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Hernandez LV, Agrawal D, Skole KS, Crockett SD, Shimpi RA, von Renteln D, Pohl H. Meeting the environmental challenges of endoscopy: a pathway from strategy to implementation. Gastrointest Endosc 2023; 98:881-888.e1. [PMID: 37977670 DOI: 10.1016/j.gie.2023.07.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 07/18/2023] [Indexed: 11/19/2023]
Affiliation(s)
- Lyndon V Hernandez
- Division of Gastroenterology and Hepatology, Oregon Health & Science University, Portland, Oregon, USA
| | - Deepak Agrawal
- Division of Gastroenterology, Duke University Medical Center, Durham, North Carolina, USA
| | - Kevin S Skole
- Department of Gastroenterology, Penn Medicine Princeton Medical Center, Plainsboro, New Jersey, USA
| | | | - Rahul A Shimpi
- Division of Gastroenterology, Montreal University Hospital Center (CHUM) and Montreal University Hospital Research Center (CRCHUM), Montreal, Quebec, Canada
| | - Daniel von Renteln
- Division of Gastroenterology and Hepatology, Dell Medical School, University Texas at Austin, Austin, Texas, USA
| | - Heiko Pohl
- Department of Gastroenterology, VA Medical Center, White River Junction, Vermont, USA; Department of Gastroenterology, VA Medical Center, White River Junction, Vermont; Dartmouth Hitchcock Medical Center, New Hampshire, USA
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Hoefs J, Harmon RS. Isotopic history of seawater: the stable isotope character of the global ocean at present and in the geological past. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2023; 59:349-411. [PMID: 37877261 DOI: 10.1080/10256016.2023.2271127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 09/10/2023] [Indexed: 10/26/2023]
Abstract
After the atmosphere, the ocean is the most well-mixed and homogeneous global geochemical reservoir. Both physical and biological processes generate elemental and isotope variations in seawater. Contrasting geochemical behaviors cause elements to be susceptible to different fractionation mechanisms, with their isotopes providing unique insights into the composition and evolution of the ocean over the course of geological history. Supplementing the traditional stable isotopes (H, C, O, N, S) that provide information about ocean processes and past environmental conditions, radiogenic isotope (Sr, Nd, Os, Pb, U) systems can be used as time markers, indicators of terrestrial weathering, and ocean water mass mixing. Recent instrumentation advances have made possible the measurement of natural stable isotope variations produced by both mass-dependent and mass-independent fractionation for an ever-increasing number of metal elements (e.g. Li, B, Mg, Si, Ca, V, Cr, Fe, Ni, Cu, Zn, Se, Mo, Cd, Tl, U). The major emphasis in this review is on the isotopic composition of the light elements based on a comparatively large literature. Unlike O, H and S, the stable isotopes of C, N and Si do not have a constant isotopic composition in the modern ocean. The major cations Ca, Mg, and Sr fixed in carbonate shells provide the best proxies for reconstruction of the composition of the ocean in the past. Exhibiting large isotope enrichments in ocean water, B and Li are suitable for the investigation of water/rock interactions and can act as monitors of former oceanic pH. The bioessential elements Zn, Cd, and Ni are indicators of paleoproductivity in the ocean. Characteristic isotope enrichments or depletions of the multivalent elements V, Cr, Fe, Se, Mo, and U record the past redox state of the ocean/atmosphere system. Case studies describe how isotopes have been used to define the seawater composition in the geological past.
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Affiliation(s)
- Jochen Hoefs
- Geowissenschaftliches Zentrum, Universität Göttingen, Göttingen, Germany
| | - Russell S Harmon
- Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA
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Steinhoefel G, Beck KK, Benthien A, Richter KU, Schmidt-Grieb GM, Bijma J. Matrix-independent boron isotope analysis of silicate and carbonate reference materials by ultraviolet femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry with application to the cold-water coral Desmophyllum dianthus. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9508. [PMID: 37072155 DOI: 10.1002/rcm.9508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 03/10/2023] [Accepted: 03/11/2023] [Indexed: 06/17/2023]
Abstract
RATIONALE Boron isotopes are a powerful tool for pH reconstruction in marine carbonates and as a tracer for fluid-mineral interaction in geochemistry. Microanalytical approaches based on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) often suffer from effects induced by the sample matrix. In this study, we investigate matrix-independent analyses of B isotopic ratios and apply this technique to cold-water corals. METHODS We employ a customized 193 nm femtosecond laser ablation system (Solstice, Spectra-Physics) coupled to a MC-ICP-MS system (Nu Plasma II, Nu Instruments) equipped with electron multipliers for in situ measurements of B isotopic ratios (11 B/10 B) at the micrometric scale. We analyzed various reference materials of silicate and carbonate matrices using non-matrix matched calibration without employing any correction. This approach was then applied to investigate defined increments in coral samples from a Chilean fjord. RESULTS We obtained accurate B isotopic ratios with a reproducibility of ±0.9‰ (2 SD) for various reference materials including silicate glasses (GOR132-G, StHs6/80-G, ATHO-G and NIST SRM 612), clay (IAEA-B-8) and carbonate (JCp-1) using the silicate glass NIST SRM 610 as calibration standard, which shows that neither laser-induced nor ICP-related matrix effects are detectable. The application to cold-water corals (Desmophyllum dianthus) reveals minor intra-skeleton variations in δ11 B with average values between 23.01‰ and 25.86‰. CONCLUSIONS Our instrumental set-up provides accurate and precise B isotopic ratios independently of the sample matrix at the micrometric scale. This approach opens a wide field of application in geochemistry, including pH reconstruction in biogenic carbonates and deciphering processes related to fluid-mineral interaction.
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Affiliation(s)
- Grit Steinhoefel
- Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut, Bremerhaven, Germany
| | - Kristina K Beck
- Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut, Bremerhaven, Germany
- Universität Bremen, Bremen, Germany
- University of Edinburgh, Edinburgh, UK
| | - Albert Benthien
- Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut, Bremerhaven, Germany
| | - Klaus-Uwe Richter
- Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut, Bremerhaven, Germany
| | | | - Jelle Bijma
- Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut, Bremerhaven, Germany
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Gong L, Holbourn A, Kuhnt W, Opdyke B, Zhang Y, Ravelo AC, Zhang P, Xu J, Matsuzaki K, Aiello I, Beil S, Andersen N. Middle Pleistocene re-organization of Australian Monsoon. Nat Commun 2023; 14:2002. [PMID: 37037802 PMCID: PMC10086051 DOI: 10.1038/s41467-023-37639-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 03/24/2023] [Indexed: 04/12/2023] Open
Abstract
The sensitivity of the Australian Monsoon to changing climate boundary conditions remains controversial due to limited understanding of forcing processes and past variability. Here, we reconstruct austral summer monsoonal discharge and wind-driven winter productivity across the Middle Pleistocene Transition (MPT) in a sediment sequence drilled off NW Australia. We show that monsoonal precipitation and runoff primarily responded to precessional insolation forcing until ~0.95 Ma, but exhibited heightened sensitivity to ice volume and pCO2 related feedbacks following intensification of glacial-interglacial cycles. Our records further suggest that summer monsoon variability at the precessional band was closely tied to the thermal evolution of the Indo-Pacific Warm Pool and strength of the Walker circulation over the past ~1.6 Myr. By contrast, productivity proxy records consistently tracked glacial-interglacial variability, reflecting changing rhythms in polar ice fluctuations and Hadley circulation strength. We conclude that the Australian Monsoon underwent a major re-organization across the MPT and that extratropical feedbacks were instrumental in driving short- and long-term variability.
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Affiliation(s)
- Li Gong
- Institute of Geosciences, Christian-Albrechts-University, D-24118, Kiel, Germany
| | - Ann Holbourn
- Institute of Geosciences, Christian-Albrechts-University, D-24118, Kiel, Germany.
| | - Wolfgang Kuhnt
- Institute of Geosciences, Christian-Albrechts-University, D-24118, Kiel, Germany
| | - Bradley Opdyke
- Research School of Earth Sciences, Australian National University, Mills Road, Acton, ACT, 2601, Australia
| | - Yan Zhang
- Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Ana Christina Ravelo
- Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Peng Zhang
- Institute of Cenozoic Geology and Environment, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, 710069, Xi'an, China
| | - Jian Xu
- Institute of Cenozoic Geology and Environment, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, 710069, Xi'an, China
| | - Kenji Matsuzaki
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Ivano Aiello
- Department of Geological Oceanography, Moss Landing Marine Laboratories, San Jose State University, Moss Landing, CA, 95039, USA
| | - Sebastian Beil
- Institute of Geosciences, Christian-Albrechts-University, D-24118, Kiel, Germany
| | - Nils Andersen
- Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, Christian-Albrechts-University Kiel, D-24118, Kiel, Germany
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Shackleton JD, Follows MJ, Thomas PJ, Omta AW. The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? CLIMATE DYNAMICS 2022; 60:4083-4098. [PMID: 37292246 PMCID: PMC10244291 DOI: 10.1007/s00382-022-06544-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 10/14/2022] [Indexed: 06/10/2023]
Abstract
Glacial-interglacial cycles constitute large natural variations in Earth's climate. The Mid-Pleistocene Transition (MPT) marks a shift of the dominant periodicity of these climate cycles from ∼ 40 to ∼ 100 kyr. Recently, it has been suggested that this shift resulted from a gradual increase in the internal period (or equivalently, a decrease in the natural frequency) of the system. As a result, the system would then have locked to ever higher multiples of the external forcing period. We find that the internal period is sensitive to the strength of positive feedbacks in the climate system. Using a carbon cycle model in which feedbacks between calcifier populations and ocean alkalinity mediate atmospheric CO2 , we simulate stepwise periodicity changes similar to the MPT through such a mechanism. Due to the internal dynamics of the system, the periodicity shift occurs up to millions of years after the change in the feedback strength is imposed. This suggests that the cause for the MPT may have occurred a significant time before the observed periodicity shift.
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Affiliation(s)
- J. D. Shackleton
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - M. J. Follows
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - P. J. Thomas
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH 44106 USA
| | - A. W. Omta
- Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, OH 44106 USA
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Erdogan S, Pata UK, Solarin SA, Okumus I. On the persistence of shocks to global CO 2 emissions: a historical data perspective (0 to 2014). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:77311-77320. [PMID: 35675017 DOI: 10.1007/s11356-022-21278-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Anthropogenic emissions of carbon dioxide (CO2) are the most important greenhouse gas. However, until now, no research has investigated the persistence of global CO2 emissions over a very long period of time. This work aims to fill this gap by examining the persistence of shocks to global CO2 emissions with a dataset of more than 2000 years. To this end, the study applies a battery of unit root tests by considering sharp and smooth structural shifts as well as the frequency domain properties of the series. Lee-Strazicich method results reveal that sharp break dates relate to the influenza pandemic of 1557 and the invention of the steam engine in 1712, and these historical events led to changes in the trend function of CO2 emissions. The findings of the Fourier Lagrange Multiplier and Fourier wavelet unit root tests illustrate that global CO2 emissions contain a unit root and do not exhibit mean-reverting behavior, thus external shocks have permanent effects on CO2 emissions. The results suggest that a reduction in global CO2 emissions is possible if effective environmental and energy policies established in international meetings such as Rio Conference, Kyoto Protocol Paris Agreement, and the United Nations Sustainable Development Summit are properly implemented.
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Affiliation(s)
- Sinan Erdogan
- Faculty of Economics and Administrative Sciences, Hatay Mustafa Kemal University, Hatay, Turkey
| | - Ugur Korkut Pata
- Faculty of Economics and Administrative Sciences, Osmaniye Korkut Ata University, Osmaniye, Turkey.
| | | | - Ilyas Okumus
- Faculty of Economics and Administrative Sciences, Kahramanmaras Sutcu Imam University, Kahramanmaras, Turkey
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Dowsett H, Jacobs P, de Mutsert K. Using paleoecological data to inform decision making: A deep-time perspective. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.972179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Latest climate models project conditions for the end of this century that are generally outside of the human experience. These future conditions affect the resilience and sustainability of ecosystems, alter biogeographic zones, and impact biodiversity. Deep-time records of paleoclimate provide insight into the climate system over millions of years and provide examples of conditions very different from the present day, and in some cases similar to model projections for the future. In addition, the deep-time paleoecologic and sedimentologic archives provide insight into how species and habitats responded to past climate conditions. Thus, paleoclimatology provides essential context for the scientific understanding of climate change needed to inform resource management policy decisions. The Pliocene Epoch (5.3–2.6 Ma) is the most recent deep-time interval with relevance to future global warming. Analysis of marine sediments using a combination of paleoecology, biomarkers, and geochemistry indicates a global mean annual temperature for the Late Pliocene (3.6–2.6 Ma) ∼3°C warmer than the preindustrial. However, the inability of state-of-the-art climate models to capture some key regional features of Pliocene warming implies future projections using these same models may not span the full range of plausible future climate conditions. We use the Late Pliocene as one example of a deep-time interval relevant to management of biodiversity and ecosystems in a changing world. Pliocene reconstructed sea surface temperatures are used to drive a marine ecosystem model for the North Atlantic Ocean. Given that boundary conditions for the Late Pliocene are roughly analogous to present day, driving the marine ecosystem model with Late Pliocene paleoenvironmental conditions allows policymakers to consider a future ocean state and associated fisheries impacts independent of climate models, informed directly by paleoclimate information.
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8
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Thomas NC, Bradbury HJ, Hodell DA. Changes in North Atlantic deep-water oxygenation across the Middle Pleistocene Transition. Science 2022; 377:654-659. [PMID: 35926027 DOI: 10.1126/science.abj7761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The oxygen concentrations of oceanic deep-water and atmospheric carbon dioxide (pCO2) are intrinsically linked through organic carbon remineralization and storage as dissolved inorganic carbon in the deep sea. We present a high-resolution reconstruction of relative changes in oxygen concentration in the deep North Atlantic for the past 1.5 million years using the carbon isotope gradient between epifaunal and infaunal benthic foraminifera species as a proxy for paleo-oxygen. We report a significant (>40 micromole per kilogram) reduction in glacial Atlantic deep-water oxygenation at ~960 thousand to 900 thousand years ago that coincided with increased continental ice volume and a major change in ocean thermohaline circulation. Paleo-oxygen results support a scenario of decreasing deep-water oxygen concentrations, increased respired carbon storage, and a reduction in glacial pCO2 across the Middle Pleistocene Transition.
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Affiliation(s)
- Nicola C Thomas
- Department of Earth Science, University of Cambridge, Cambridge, UK
| | | | - David A Hodell
- Department of Earth Science, University of Cambridge, Cambridge, UK
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9
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Wang Y, Pei W, Yang J, Fan Y, Zhang R, Li T, Russell J, Zhang F, Yu X, Hu J, Song Y, Liu Z, Guan M, Han Q. The relationship between volcanism and global climate changes in the Tropical Western Pacific over the mid-Pleistocene transition: Evidence from mercury concentration and isotopic composition. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 823:153482. [PMID: 35122862 DOI: 10.1016/j.scitotenv.2022.153482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/24/2022] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Volcanoes are a significant component of the Earth system, influencing the interaction between oceans and the atmosphere over large spatial and temporal scales. Being a volcanically dynamic region, the Tropical Western Pacific (TWP) can significantly impact variations in global climate. However, high-resolution continuous records of volcanic activity in this region are lacking, resulting in significant uncertainties regarding the coupling between the deep earth, climate changes, and atmospheric CO2 in the TWP. To address this issue, mercury (Hg) levels, isotopic compositions, and Hg/total organic carbon (Hg/TOC) ratios were determined at site U1486 to track volcanic activity throughout the mid-Pleistocene transition (MPT) from 1.3 Myr to 0.6 Myr. Our results of anomalously high Hg concentrations and Hg/TOC ratios provide evidence of time-varying volcanism throughout the MPT. Mercury isotopes in the Hg-enriched sediments were characterized by near-zero Δ199Hg values, which is consistent with volcanism acting as the primary source of Hg to the sediments. Spectral analysis of the Hg/TOC ratio showed significant periodicity at ~100 kyr and ~ 23 kyr as well as a weaker signal at ~41 kyr consistent with Milankovitch cycles. A cross spectral analysis of Hg/TOC and the LR04 δ18O stack record suggests that the peak in volcanism lags the temperature minimum by ~6 kyr, and occurs prior to the δ18O minimum known as the glacial termination by ~14 ± 2 kyr. The records of volcanic activity in this site are also consistent with a prominent rise in atmospheric CO2 and negative excursion of benthic carbon isotopes throughout the MPT. This study provides direct sedimentary evidence in the TWP of the feedback between volcanic activity, climate change and atmospheric CO2.
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Affiliation(s)
- Yipeng Wang
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Wenlong Pei
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Jialei Yang
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Yujin Fan
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Rui Zhang
- Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China; Jiangsu Key Laboratory of Marine Bioresources and Environment, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China; School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China; Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA.
| | - Tiegang Li
- First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, Shandong Province, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - James Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - Fan Zhang
- Department of Chemical Engineering, Jiangsu Ocean University, 222005, Jiangsu Province, China
| | - Xiaoxiao Yu
- State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Junjie Hu
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Yuehuo Song
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Zhiyong Liu
- School of Radiation Medicine and Protection, Medicine College, Soochow University, Suzhou 215123, Jiangsu Province, China
| | - Minglei Guan
- School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China
| | - Qi Han
- School of Ocean Sciences, China University of Geosciences, Beijing 100083, China
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Geochronological Evidence Inferring Carbonate Compensation Depth Shoaling in the Philippine Sea after the Mid-Brunhes Event. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2022. [DOI: 10.3390/jmse10060745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Carbonate compensation depth (CCD) is an important factor in the global deep ocean and in global carbon cycling; however, its variabilities have not been well documented in previous studies. In this study, we investigate two deep-sea cores collected from the Philippine Sea in terms of geochronology and geochemical properties over the past ~900 kyr. The principle results are as follows: (1) Two magnetozones are determined from the sediment’s magnetic records, which can be correlated with the Brunhes and Matuyama chrons in the geomagnetic polarity timescale. (2) The age models can be refined by tuning the Ba and Sm intensities of the two studied cores to the global ice volume, and the estimated sediment accumulation rate is ~4 mm/kyr. (3) Chalky mud and the bulk carbon δ13C record vary abruptly at ~430 ka and imply 200 m shoaling of the CCD. Based on these results, a close link is inferred between marine productivity, aeolian dust, and CCD changes, which can be correlated with a major change that occurred during the Mid-Brunhes Event. Therefore, we propose that the sedimentary processes in the Philippine Sea are evidence of global climate change, providing a unique window to observe interactions between various environmental systems.
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11
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Evidence for a Northern Hemispheric trigger of the 100,000-y glacial cyclicity. Proc Natl Acad Sci U S A 2021; 118:2020260118. [PMID: 34750249 DOI: 10.1073/pnas.2020260118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2021] [Indexed: 11/18/2022] Open
Abstract
The causes of the Mid-Pleistocene Transition, the shift from ∼41-ky to 100-ky interglacial-glacial cycles and more intense ice ages, remain intensely debated, as this fundamental change occurred between ∼1,250 and 650 ka without substantial changes in astronomical climate forcings. Recent studies disagree about the relative importance of events and processes in the Northern and Southern Hemispheres, as well as whether the shift occurred gradually over several interglacial-glacial cycles or abruptly at ∼900 ka. We address these issues using a north-to-south reconstruction of the Atlantic arm of the global meridional overturning ocean circulation, a primary means for distributing heat around the globe, using neodymium (Nd) isotopes. Results reveal a period of intense erosion affecting the cratonic shields surrounding the North Atlantic between Marine Isotope Stages (MIS) 27 and 25 (∼980 and 950 ka), reflected by unusually low Nd isotope ratios in deep North Atlantic seawater. This episode preceded a major ocean circulation weakening between MIS 25 and 21 (950 and 860 ka) that coincided with the first ∼100-ky-long interglacial-glacial onset of Northern Hemisphere glaciation at around 2.4 to 2.8 Ma. The data point to a Northern Hemisphere-sourced initiation for the transition, possibly induced through regolith loss and increased exposure of the crystalline bedrock, which would lead to increased friction, enabling larger ice sheets that are characteristic of the 100-ky interglacial-glacial cycles.
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12
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Pliocene decoupling of equatorial Pacific temperature and pH gradients. Nature 2021; 598:457-461. [PMID: 34671138 DOI: 10.1038/s41586-021-03884-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 08/06/2021] [Indexed: 02/08/2023]
Abstract
Ocean dynamics in the equatorial Pacific drive tropical climate patterns that affect marine and terrestrial ecosystems worldwide. How this region will respond to global warming has profound implications for global climate, economic stability and ecosystem health. As a result, numerous studies have investigated equatorial Pacific dynamics during the Pliocene (5.3-2.6 million years ago) and late Miocene (around 6 million years ago) as an analogue for the future behaviour of the region under global warming1-12. Palaeoceanographic records from this time present an apparent paradox with proxy evidence of a reduced east-west sea surface temperature gradient along the equatorial Pacific1,3,7,8-indicative of reduced wind-driven upwelling-conflicting with evidence of enhanced biological productivity in the east Pacific13-15 that typically results from stronger upwelling. Here we reconcile these observations by providing new evidence for a radically different-from-modern circulation regime in the early Pliocene/late Miocene16 that results in older, more acidic and more nutrient-rich water reaching the equatorial Pacific. These results provide a mechanism for enhanced productivity in the early Pliocene/late Miocene east Pacific even in the presence of weaker wind-driven upwelling. Our findings shed new light on equatorial Pacific dynamics and help to constrain the potential changes they will undergo in the near future, given that the Earth is expected to reach Pliocene-like levels of warming in the next century.
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13
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Renforth P, Campbell JS. The role of soils in the regulation of ocean acidification. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200174. [PMID: 34365827 PMCID: PMC8349639 DOI: 10.1098/rstb.2020.0174] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/14/2021] [Indexed: 01/22/2023] Open
Abstract
Soils play an important role in mediating chemical weathering reactions and carbon transfer from the land to the ocean. Proposals to increase the contribution of alkalinity to the oceans through 'enhanced weathering' as a means to help prevent climate change are gaining increasing attention. This would augment the existing connection between the biogeochemical function of soils and alkalinity levels in the ocean. The feasibility of enhanced weathering depends on the combined influence of what minerals are added to soils, the formation of secondary minerals in soils and the drainage regime, and the partial pressure of respired CO2 around the dissolving mineral. Increasing the alkalinity levels in the ocean through enhanced weathering could help to ameliorate the effects of ocean acidification in two ways. First, enhanced weathering would slightly elevate the pH of drainage waters, and the receiving coastal waters. The elevated pH would result in an increase in carbonate mineral saturation states, and a partial reversal in the effects of elevated CO2. Second, the increase in alkalinity would help to replenish the ocean's buffering capacity by maintaining the 'Revelle Factor', making the oceans more resilient to further CO2 emissions. However, there is limited research on the downstream and oceanic impacts of enhanced weathering on which to base deployment decisions. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.
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Affiliation(s)
- P. Renforth
- The Research Centre for Carbon Solutions, Heriot-Watt University, Edinburgh EH14 4AS, UK
| | - J. S. Campbell
- The Research Centre for Carbon Solutions, Heriot-Watt University, Edinburgh EH14 4AS, UK
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1.36 million years of Mediterranean forest refugium dynamics in response to glacial-interglacial cycle strength. Proc Natl Acad Sci U S A 2021; 118:2026111118. [PMID: 34400496 DOI: 10.1073/pnas.2026111118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The sediment record from Lake Ohrid (Southwestern Balkans) represents the longest continuous lake archive in Europe, extending back to 1.36 Ma. We reconstruct the vegetation history based on pollen analysis of the DEEP core to reveal changes in vegetation cover and forest diversity during glacial-interglacial (G-IG) cycles and early basin development. The earliest lake phase saw a significantly different composition rich in relict tree taxa and few herbs. Subsequent establishment of a permanent steppic herb association around 1.2 Ma implies a threshold response to changes in moisture availability and temperature and gradual adjustment of the basin morphology. A change in the character of G-IG cycles during the Early-Middle Pleistocene Transition is reflected in the record by reorganization of the vegetation from obliquity- to eccentricity-paced cycles. Based on a quantitative analysis of tree taxa richness, the first large-scale decline in tree diversity occurred around 0.94 Ma. Subsequent variations in tree richness were largely driven by the amplitude and duration of G-IG cycles. Significant tree richness declines occurred in periods with abundant dry herb associations, pointing to aridity affecting tree population survival. Assessment of long-term legacy effects between global climate and regional vegetation change reveals a significant influence of cool interglacial conditions on subsequent glacial vegetation composition and diversity. This effect is contrary to observations at high latitudes, where glacial intensity is known to control subsequent interglacial vegetation, and the evidence demonstrates that the Lake Ohrid catchment functioned as a refugium for both thermophilous and temperate tree species.
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Biller-Celander N, Shakun JD, McGee D, Wong CI, Reyes AV, Hardt B, Tal I, Ford DC, Lauriol B. Increasing Pleistocene permafrost persistence and carbon cycle conundrums inferred from Canadian speleothems. SCIENCE ADVANCES 2021; 7:7/18/eabe5799. [PMID: 33910910 PMCID: PMC8081356 DOI: 10.1126/sciadv.abe5799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 03/10/2021] [Indexed: 06/12/2023]
Abstract
Permafrost carbon represents a potentially powerful amplifier of climate change, but little is known about permafrost sensitivity and associated carbon cycling during past warm intervals. We reconstruct permafrost history in western Canada during Pleistocene interglacials from 130 uranium-thorium ages on 72 speleothems, cave deposits that only accumulate with deep ground thaw. We infer that permafrost thaw extended to the high Arctic during one or more periods between ~1.5 million and 0.5 million years ago but has been limited to the sub-Arctic since 400,000 years ago. Our Canadian speleothem growth history closely parallels an analogous reconstruction from Siberia, suggesting that this shift toward more stable permafrost across the Pleistocene may have been Arctic-wide. In contrast, interglacial greenhouse gas concentrations were relatively stable throughout the Pleistocene, suggesting that either permafrost thaw did not trigger substantial carbon release to the atmosphere or it was offset by carbon uptake elsewhere on glacial-interglacial time scales.
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Affiliation(s)
- Nicole Biller-Celander
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
| | - Jeremy D Shakun
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA.
| | - David McGee
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Corinne I Wong
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
| | - Alberto V Reyes
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
| | - Ben Hardt
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Irit Tal
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Derek C Ford
- Department of Geography and Earth Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Bernard Lauriol
- Department of Geography, Environment and Geomatics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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16
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Pascual F. CO2 and Lung Function: An in Vivo Exploration of Potential Climate Change Implications. ENVIRONMENTAL HEALTH PERSPECTIVES 2021; 129:34002. [PMID: 33750192 PMCID: PMC7984582 DOI: 10.1289/ehp8975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 02/16/2021] [Indexed: 06/12/2023]
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17
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Larcombe AN, Papini MG, Chivers EK, Berry LJ, Lucas RM, Wyrwoll CS. Mouse Lung Structure and Function after Long-Term Exposure to an Atmospheric Carbon Dioxide Level Predicted by Climate Change Modeling. ENVIRONMENTAL HEALTH PERSPECTIVES 2021; 129:17001. [PMID: 33439053 PMCID: PMC7805407 DOI: 10.1289/ehp7305] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 11/30/2020] [Accepted: 12/03/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND Climate change models predict that atmospheric carbon dioxide [CO2] levels will be between 700 and 900 ppm within the next 80 y. Despite this, the direct physiological effects of exposure to slightly elevated atmospheric CO2 (as compared with ∼410 ppm experienced today), especially when exposures extend from preconception to adulthood, have not been thoroughly studied. OBJECTIVES In this study we aimed to assess the respiratory structure and function effects of long-term exposure to 890 ppm CO2 from preconception to adulthood using a mouse model. METHODS We exposed mice to CO2 (∼890 ppm) from prepregnancy, through the in utero and early life periods, until 3 months of age, at which point we assessed respiratory function using the forced oscillation technique, and lung structure. RESULTS CO2 exposure resulted in a range of respiratory impairments, particularly in female mice, including higher tissue elastance, longer chord length, and lower lung compliance. Importantly, we also assessed the lung function of the dams that gave birth to our experimental subjects. Even though these mice had been exposed to the same level of increased CO2 for a similar amount of time (∼8wk), we measured no impairments in lung function. This suggests that the early life period, when lungs are undergoing rapid growth and development, is particularly sensitive to CO2. DISCUSSION To the best of our knowledge, this study, for the first time, shows that long-term exposure to environmentally relevant levels of CO2 can impact respiratory function in the mouse. https://doi.org/10.1289/EHP7305.
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Affiliation(s)
- Alexander N. Larcombe
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
- Occupation, Environment and Safety, School of Population Health, Curtin University, Perth, Australia
| | - Melissa G. Papini
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
- School of Human Sciences, University of Western Australia, Nedlands, Western Australia, Australia
| | - Emily K. Chivers
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
| | - Luke J. Berry
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
| | - Robyn M. Lucas
- National Centre for Epidemiology and Population Health, Research School of Population Health, College of Health and Medicine, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Caitlin S. Wyrwoll
- School of Human Sciences, University of Western Australia, Nedlands, Western Australia, Australia
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18
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Resonantly Forced Baroclinic Waves in the Oceans: A New Approach to Climate Variability. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2020. [DOI: 10.3390/jmse9010013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
How variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary are probably one of the greatest mysteries of modern climate science. These changes in the forcing are too small to explain the observed climate variations as simple linear responses. Consequently, to strictly apply the Milankovitch’s theory, a mediator involving positive feedbacks must be found, endowing the climate response with a resonant feature. This mediation should help explain the Mid-Pleistocene Transition (MPT) by involving orbital variations as the only external forcing, contrary to the current theory that supposes the coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. Supported by both observational and theoretical considerations, recent work shows that long-period Rossby waves winding around subtropical ocean gyres meet the requirements of the sought mediator. Propagating cyclonically around the subtropical gyres, the so-called Gyral Rossby waves (GRWs) owe their origin to the gradient β of the Coriolis parameter relative to the mean radius of the gyres. The resulting modulated western boundary current, whose velocity is added to that of the steady anticyclonic wind-driven current, accelerates/decelerates according to the phase of GRWs. This amplifies the oscillation of the thermocline because of a positive feedback loop ensuing from the temperature gradient between the high and low latitudes of the gyres. Multi-frequency GRWs overlap, behaving as coupled oscillators with inertia resonantly forced by solar and orbital cycles in subharmonic modes. So, the efficiency of forcing increases considerably as the forcing period approaches a natural period of the GRWs. Taking advantage of (1) the alkenone paleothermometer in sediment cores sampled in the Tasman Sea floor, we show that, in the same way as during the MPT, but with periods 10 times longer, a transition occurred at the hinge of Pliocene-Pleistocene. Both transitions as well as the observed adjustment of the South Pacific gyre to the resonance conditions during the MPT are explained from orbital forcing alone—(2) data set of individual Globigerinoides ruberδO 18 spanning the Holocene and the Last Glacial Maximum from sediment core in the eastern equatorial Pacific, we show how the El Niño–Southern Oscillation (ENSO) activity is modulated according to subharmonic modes. Periods of warming induce a decrease in ENSO activity while periods of cooling induce an increase.
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Köhler P, van de Wal RSW. Interglacials of the Quaternary defined by northern hemispheric land ice distribution outside of Greenland. Nat Commun 2020; 11:5124. [PMID: 33046715 PMCID: PMC7550566 DOI: 10.1038/s41467-020-18897-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 09/18/2020] [Indexed: 11/16/2022] Open
Abstract
Glacial/interglacial dynamics during the Quaternary were suggested to be mainly driven by obliquity (41-kyr periodicity), including irregularities during the last 1 Myr that resulted in on average 100-kyr cycles. Here, we investigate this so-called Mid-Pleistocene Transition via model-based deconvolution of benthic δ18O, redefining interglacials by lack of substantial northern hemispheric land ice outside of Greenland. We find that in 67%, 88% and 52% of the obliquity cycles during the early, middle and late Quaternary, respectively, a glacial termination is realized leading to irregular appearances of new interglacials during various parts of the last 2.6 Myr. This finding suggests that the proposed idea of terminations leading to new interglacials in the Quaternary as obliquity driven with growing influence of land ice volume on the timing of deglaciations during the last 1 Myr might be too simple. Alternatively, the land ice-based definition of interglacials needs revision if applied to the entire Quaternary. This study presents a new definition of interglacials during the Quaternary. The authors find the appearance of interglacials is in general following the 41-kyr cycle of obliquity with various exceptions, suggesting a more complex physical mechanism triggering glacial terminations.
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Affiliation(s)
- Peter Köhler
- Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI), P.O. Box 12 01 61, Bremerhaven, 27515, Germany.
| | - Roderik S W van de Wal
- Institute for Marine and Atmospheric Research Utrecht (IMAU) and Faculty of Geosciences, Department of Physical Geography, Utrecht University, Princetonplein 5, Utrecht, 3584 CC, The Netherlands
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20
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Modelling the effects of CO 2 on C 3 and C 4 grass competition during the mid-Pleistocene transition in South Africa. Sci Rep 2020; 10:16234. [PMID: 33004831 PMCID: PMC7530989 DOI: 10.1038/s41598-020-72614-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 09/02/2020] [Indexed: 11/25/2022] Open
Abstract
Palaeoenvironmental reconstructions of the interior of South Africa show a wetter environment than today and a non-analogous vegetation structure in the Early Pleistocene. This includes the presence of grasses following both C3 and C4 photosynthetic pathways, whereas C3 grasses decline after the mid-Pleistocene transition (MPT, c. 1.2–0.8 Ma). However, the local terrestrial proxy record cannot distinguish between the potential drivers of these vegetation changes. In this study we show that low glacial CO2 levels, similar to those at the MPT, lead to the local decline of C3 grasses under conditions of decreased water availability, using a vegetation model (LPX) driven by Atmosphere–Ocean coupled General Climate Model climate reconstructions. We modelled vegetation for glacial climates under different levels of CO2 and fire regimes and find evidence that a combination of low CO2 and changed seasonality is driving the changes in grass cover, whereas fire has little influence on the ratio of C3:C4 grasses. Our results suggest the prevalence of a less vegetated landscape with limited, seasonal water availability, which could potentially explain the much sparser mid-Pleistocene archaeological record in the southern Kalahari.
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21
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de la Vega E, Chalk TB, Wilson PA, Bysani RP, Foster GL. Atmospheric CO 2 during the Mid-Piacenzian Warm Period and the M2 glaciation. Sci Rep 2020; 10:11002. [PMID: 32647351 PMCID: PMC7347535 DOI: 10.1038/s41598-020-67154-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 05/18/2020] [Indexed: 11/28/2022] Open
Abstract
The Piacenzian stage of the Pliocene (2.6 to 3.6 Ma) is the most recent past interval of sustained global warmth with mean global temperatures markedly higher (by ~2–3 °C) than today. Quantifying CO2 levels during the mid-Piacenzian Warm Period (mPWP) provides a means, therefore, to deepen our understanding of Earth System behaviour in a warm climate state. Here we present a new high-resolution record of atmospheric CO2 using the δ11B-pH proxy from 3.35 to 3.15 million years ago (Ma) at a temporal resolution of 1 sample per 3–6 thousand years (kyrs). Our study interval covers both the coolest marine isotope stage of the mPWP, M2 (~3.3 Ma) and the transition into its warmest phase including interglacial KM5c (centered on ~3.205 Ma) which has a similar orbital configuration to present. We find that CO2 ranged from \documentclass[12pt]{minimal}
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\begin{document}$${{\bf{394}}}_{{\boldsymbol{-}}{\bf{9}}}^{{\boldsymbol{+}}{\bf{34}}}$$\end{document}394−9+34 ppm to \documentclass[12pt]{minimal}
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\begin{document}$${{\bf{330}}}_{{\boldsymbol{-}}{\bf{21}}}^{{\boldsymbol{+}}{\bf{14}}}$$\end{document}330−21+14 ppm: with CO2 during the KM5c interglacial being \documentclass[12pt]{minimal}
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\begin{document}$${{\bf{391}}}_{{\boldsymbol{-}}{\bf{28}}}^{{\boldsymbol{+}}{\bf{30}}}$$\end{document}391−28+30 ppm (at 95% confidence). Our findings corroborate the idea that changes in atmospheric CO2 levels played a distinct role in climate variability during the mPWP. They also facilitate ongoing data-model comparisons and suggest that, at present rates of human emissions, there will be more CO2 in Earth’s atmosphere by 2025 than at any time in at least the last 3.3 million years.
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Affiliation(s)
- Elwyn de la Vega
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton,Waterfront Campus Southampton, Southampton, SO14 3ZH, UK.
| | - Thomas B Chalk
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton,Waterfront Campus Southampton, Southampton, SO14 3ZH, UK
| | - Paul A Wilson
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton,Waterfront Campus Southampton, Southampton, SO14 3ZH, UK
| | - Ratna Priya Bysani
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton,Waterfront Campus Southampton, Southampton, SO14 3ZH, UK
| | - Gavin L Foster
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton,Waterfront Campus Southampton, Southampton, SO14 3ZH, UK
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22
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Arnaut LG, Ibáñez S. Self-sustained oscillations and global climate changes. Sci Rep 2020; 10:11200. [PMID: 32641755 PMCID: PMC7343778 DOI: 10.1038/s41598-020-68052-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 05/29/2020] [Indexed: 11/29/2022] Open
Abstract
The periodic changes of atmospheric CO2 and temperature over the last 5 Myr reveal three features that challenge current climate research, namely: (i) the mid-Pleistocene transition of dominant 41-kyr cycles to dominant 100-kyr cycles, (ii) the absence of a strong precession signal of approximately 20 kyr, and (iii) the cooling through the middle and late Holocene. These features are not directly addressable by Earth's orbital changes described by Milankovitch. Here we show that a closed photochemical system exposed to a constant illumination source can sustain oscillations. In this simple conceptual model, the oscillations are intrinsic to the system and occur even in the absence of periodic radiative forcing. With proper adaptations to the Earth system, this oscillator explains the main features of past climate dynamics. Our model places photosynthesis and the carbon cycle as key drivers of climate change. We use this model to predict the relaxation of a 1,000 PgC pulse of CO2. The removal of 50% of this CO2 will require one century, and will lead to a warmer and wetter future. However, more pronounced glaciation cycles emerge on the millennial timescale.
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Affiliation(s)
- Luis G Arnaut
- Chemistry Department, University of Coimbra, Coimbra, Portugal.
| | - Santiago Ibáñez
- Departamento de Matemáticas, Universidad de Oviedo, Oviedo, Spain
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23
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Zhao Y, Tzedakis PC, Li Q, Qin F, Cui Q, Liang C, Birks HJB, Liu Y, Zhang Z, Ge J, Zhao H, Felde VA, Deng C, Cai M, Li H, Ren W, Wei H, Yang H, Zhang J, Yu Z, Guo Z. Evolution of vegetation and climate variability on the Tibetan Plateau over the past 1.74 million years. SCIENCE ADVANCES 2020; 6:eaay6193. [PMID: 32494698 PMCID: PMC7202886 DOI: 10.1126/sciadv.aay6193] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 02/13/2020] [Indexed: 05/22/2023]
Abstract
The Tibetan Plateau exerts a major influence on Asian climate, but its long-term environmental history remains largely unknown. We present a detailed record of vegetation and climate changes over the past 1.74 million years in a lake sediment core from the Zoige Basin, eastern Tibetan Plateau. Results show three intervals with different orbital- and millennial-scale features superimposed on a stepwise long-term cooling trend. The interval of 1.74-1.54 million years ago is characterized by an insolation-dominated mode with strong ~20,000-year cyclicity and quasi-absent millennial-scale signal. The interval of 1.54-0.62 million years ago represents a transitional insolation-ice mode marked by ~20,000- and ~40,000-year cycles, with superimposed millennial-scale oscillations. The past 620,000 years are characterized by an ice-driven mode with 100,000-year cyclicity and less frequent millennial-scale variability. A pronounced transition occurred 620,000 years ago, as glacial cycles intensified. These new findings reveal how the interaction of low-latitude insolation and high-latitude ice-volume forcing shaped the evolution of the Tibetan Plateau climate.
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Affiliation(s)
- Yan Zhao
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Polychronis C. Tzedakis
- Environmental Change Research Centre, Department of Geography, University College London, Gower Street, London WC1E 6BT, UK
| | - Quan Li
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Feng Qin
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiaoyu Cui
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Chen Liang
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - H. John B. Birks
- Environmental Change Research Centre, Department of Geography, University College London, Gower Street, London WC1E 6BT, UK
- Department of Biological Sciences and Bjerknes Centre for Climate Research, University of Bergen, PO Box 7803, N-5020 Bergen, Norway
| | - Yaoliang Liu
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhiyong Zhang
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
- Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang 332900, China
| | - Junyi Ge
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
- CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China
| | - Hui Zhao
- Key Laboratory of Desert and Desertification, Cold and Arid Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Vivian A. Felde
- Department of Biological Sciences and Bjerknes Centre for Climate Research, University of Bergen, PO Box 7803, N-5020 Bergen, Norway
| | - Chenglong Deng
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Maotang Cai
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Huan Li
- Department of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands
| | - Weihe Ren
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Haicheng Wei
- Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China
| | - Hanfei Yang
- Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Jiawu Zhang
- MOE Key Laboratory of Western China’s Environmental Systems, Lanzhou University, Lanzhou 730000, China
| | - Zicheng Yu
- Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18015, USA
- Northeast Normal University, Changchun, China
| | - Zhengtang Guo
- University of Chinese Academy of Sciences, Beijing 100049, China
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
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24
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Two-million-year-old snapshots of atmospheric gases from Antarctic ice. Nature 2019; 574:663-666. [PMID: 31666720 DOI: 10.1038/s41586-019-1692-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 08/02/2019] [Indexed: 11/09/2022]
Abstract
Over the past eight hundred thousand years, glacial-interglacial cycles oscillated with a period of one hundred thousand years ('100k world'1). Ice core and ocean sediment data have shown that atmospheric carbon dioxide, Antarctic temperature, deep ocean temperature, and global ice volume correlated strongly with each other in the 100k world2-6. Between about 2.8 and 1.2 million years ago, glacial cycles were smaller in magnitude and shorter in duration ('40k world'7). Proxy data from deep-sea sediments suggest that the variability of atmospheric carbon dioxide in the 40k world was also lower than in the 100k world8-10, but we do not have direct observations of atmospheric greenhouse gases from this period. Here we report the recovery of stratigraphically discontinuous ice more than two million years old from the Allan Hills Blue Ice Area, East Antarctica. Concentrations of carbon dioxide and methane in ice core samples older than two million years have been altered by respiration, but some younger samples are pristine. The recovered ice cores extend direct observations of atmospheric carbon dioxide, methane, and Antarctic temperature (based on the deuterium/hydrogen isotope ratio δDice, a proxy for regional temperature) into the 40k world. All climate properties before eight hundred thousand years ago fall within the envelope of observations from continuous deep Antarctic ice cores that characterize the 100k world. However, the lowest measured carbon dioxide and methane concentrations and Antarctic temperature in the 40k world are well above glacial values from the past eight hundred thousand years. Our results confirm that the amplitudes of glacial-interglacial variations in atmospheric greenhouse gases and Antarctic climate were reduced in the 40k world, and that the transition from the 40k to the 100k world was accompanied by a decline in minimum carbon dioxide concentrations during glacial maxima.
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Abstract
Quantifying ancient atmospheric pCO2 provides valuable insights into the interplay between greenhouse gases and global climate. Beyond the 800-ky history uncovered by ice cores, discrepancies in both the trend and magnitude of pCO2 changes remain among different proxy-derived results. The traditional paleosol pCO2 paleobarometer suffers from largely unconstrained soil-respired CO2 concentration (S(z)). Using finely disseminated carbonates precipitated in paleosols from the Chinese Loess Plateau, here we identified that their S(z) can be quantitatively constrained by soil magnetic susceptibility. Based on this approach, we reconstructed pCO2 during 2.6–0.9 Ma, which documents overall low pCO2 levels (<300 ppm) comparable with ice core records, indicating that the Earth system has operated under late Pleistocene pCO2 levels for an extended period. The pCO2 levels do not show statistically significant differences across the mid-Pleistocene Transition (ca. 1.2–0.8 Ma), suggesting that CO2 is probably not the driver of this important climate change event. Climate dynamics in Earth’s distant history can provide important forecasting for future changes, but uncertainties in proxy-derived carbon dioxide results are common. Here Da and colleagues present a refined paleosol proxy for carbon dioxide reconstruction, and report persistently low levels ( < 300 ppm) throughout the Pleistocene interglacials.
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26
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Hasenfratz AP, Jaccard SL, Martínez-García A, Sigman DM, Hodell DA, Vance D, Bernasconi SM, Kleiven HKF, Haumann FA, Haug GH. The residence time of Southern Ocean surface waters and the 100,000-year ice age cycle. Science 2019; 363:1080-1084. [PMID: 30846597 DOI: 10.1126/science.aat7067] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 01/23/2019] [Indexed: 11/02/2022]
Abstract
From 1.25 million to 700,000 years ago, the ice age cycle deepened and lengthened from 41,000- to 100,000-year periodicity, a transition that remains unexplained. Using surface- and bottom-dwelling foraminifera from the Antarctic Zone of the Southern Ocean to reconstruct the deep-to-surface supply of water during the ice ages of the past 1.5 million years, we found that a reduction in deep water supply and a concomitant freshening of the surface ocean coincided with the emergence of the high-amplitude 100,000-year glacial cycle. We propose that this slowing of deep-to-surface circulation (i.e., a longer residence time for Antarctic surface waters) prolonged ice ages by allowing the Antarctic halocline to strengthen, which increased the resistance of the Antarctic upper water column to orbitally paced drivers of carbon dioxide release.
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Affiliation(s)
- Adam P Hasenfratz
- Geological Institute, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland. .,Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Samuel L Jaccard
- Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland.
| | | | - Daniel M Sigman
- Department of Geosciences, Guyot Hall, Princeton University, Princeton, NJ, USA
| | - David A Hodell
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Derek Vance
- Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
| | - Stefano M Bernasconi
- Geological Institute, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
| | - Helga Kikki F Kleiven
- Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
| | - F Alexander Haumann
- British Antarctic Survey, Cambridge, UK.,Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA
| | - Gerald H Haug
- Geological Institute, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland.,Max Planck Institute for Chemistry, Mainz, Germany
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Chen XY, Teng FZ, Catling DC. Fast and precise boron isotopic analysis of carbonates and seawater using Nu Plasma II multi-collector inductively coupled plasma mass spectrometry and a simple sample introduction system. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:1169-1178. [PMID: 30989736 DOI: 10.1002/rcm.8456] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 04/03/2019] [Accepted: 04/05/2019] [Indexed: 06/09/2023]
Abstract
RATIONALE The boron (B) isotopic composition in marine carbonates provides important insights into paleoclimate reconstruction and biomineralization. However, precise and accurate measurements of B isotopes using plasma-based mass spectrometry is difficult due to the volatile nature of B, which typically requires complex and more specialized sample introduction systems. Existing analytical protocols have mostly been based on Thermo Scientific Neptune Plus multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) instruments, whereas methods based on Nu Plasma mass spectrometers are scarce. METHODS We have developed a simplified analytical protocol using Nu Plasma II MC-ICPMS with standard glass sample introduction systems. Boron extraction and purification were conducted using a two-stage column chemistry with cation-exchange and Amberlite IRA 743 B-specific resin. A sample drying step was avoided, which allows for direct isotopic analysis after column chemistry. A wet plasma mode with a standard glass cyclonic spray chamber and a glass nebulizer was used instead of a more specialized perfluoroalkoxy (PFA) sample introduction system. Low residual B signals were achieved with a relatively short period of wash-out with 0.5 N HNO3 . RESULTS The external precision is better than 0.30‰ (2SD) calculated from the long-term bracketing standard, NIST SRM 951a. The overall robustness of the method was demonstrated by measurements of the international carbonate standard JCp-1 (δ11 B = +24.49 ± 0.36‰, 2SD) and seawater (δ11 B = +39.98 ± 0.35‰), which are consistent with reported values. CONCLUSIONS Our method provides an alternative approach for B isotope analysis using a routine wet plasma MC-ICPMS setup that can facilitate geochemical and environmental application of B isotopes.
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Affiliation(s)
- Xin-Yang Chen
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, 98195, USA
| | - Fang-Zhen Teng
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, 98195, USA
| | - David C Catling
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, 98195, USA
- Astrobiology Program/Virtual Planetary Laboratory Team, NASA Astrobiology Institute, Seattle, WA, 98195, USA
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28
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Neogene cooling driven by land surface reactivity rather than increased weathering fluxes. Nature 2019; 571:99-102. [DOI: 10.1038/s41586-019-1332-y] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 04/26/2019] [Indexed: 11/09/2022]
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Willeit M, Ganopolski A, Calov R, Brovkin V. Mid-Pleistocene transition in glacial cycles explained by declining CO 2 and regolith removal. SCIENCE ADVANCES 2019; 5:eaav7337. [PMID: 30949580 PMCID: PMC6447376 DOI: 10.1126/sciadv.aav7337] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 02/08/2019] [Indexed: 05/03/2023]
Abstract
Variations in Earth's orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2 and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2 decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2 decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2 concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.
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Affiliation(s)
- M. Willeit
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
- Corresponding author.
| | - A. Ganopolski
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - R. Calov
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - V. Brovkin
- Max Planck Institute for Meteorology, Hamburg, Germany
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30
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31
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Diverse manifestations of the mid-Pleistocene climate transition. Nat Commun 2019; 10:352. [PMID: 30664647 PMCID: PMC6341081 DOI: 10.1038/s41467-018-08257-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 12/20/2018] [Indexed: 12/03/2022] Open
Abstract
The mid-Pleistocene transition (MPT) is widely recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles, which largely reflects integrated changes in global ice volume, sea level, and ocean temperature from the marine realm. However, much less is known about monsoon-induced terrestrial vegetation change across the MPT. Here, on the basis of a 1.7-million-year δ13C record of loess carbonates from the Chinese Loess Plateau, we document a unique MPT reflecting terrestrial vegetation changes from a dominant 23-kyr periodicity before 1.2 Ma to combined 100, 41, and 23-kyr cycles after 0.7 Ma, very different from the conventional MPT characteristics. Model simulations further reveal that the MPT transition likely reflects decreased sensitivity of monsoonal hydroclimate to insolation forcing as the Northern Hemisphere became increasingly glaciated through the MPT. Our proxy-model comparison suggests varied responses of temperature and precipitation to astronomical forcing under different ice/CO2 boundary conditions, which greatly improves our understanding of monsoon variability and dynamics from the natural past to the anthropogenic future. The mid-Pleistocene transition is recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles. Here the authors present a unique mid-Pleistocene transition of coupled monsoon-vegetation changes from 23- to 100-kyr cycles, which indicates varied sensitivity of past climate to astronomical and ice/CO2 forcing.
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Closure of the Bering Strait caused Mid-Pleistocene Transition cooling. Nat Commun 2018; 9:5386. [PMID: 30568245 PMCID: PMC6300599 DOI: 10.1038/s41467-018-07828-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Accepted: 11/28/2018] [Indexed: 11/17/2022] Open
Abstract
The Mid-Pleistocene Transition (MPT) is characterised by cooling and lengthening glacial cycles from 600–1200 ka, thought to be driven by reductions in glacial CO2 in particular from ~900 ka onwards. Reduced high latitude upwelling, a process that retains CO2 within the deep ocean over glacials, could have aided drawdown but has so far not been constrained in either hemisphere over the MPT. Here, we find that reduced nutrient upwelling in the Bering Sea, and North Pacific Intermediate Water expansion, coincided with the MPT and became more persistent at ~900 ka. We propose reduced upwelling was controlled by expanding sea ice and North Pacific Intermediate Water formation, which may have been enhanced by closure of the Bering Strait. The regional extent of North Pacific Intermediate Water across the subarctic northwest Pacific would have contributed to lower atmospheric CO2 and global cooling during the MPT. The causes of Mid-Pleistocene Transition global cooling 1 million years ago are still unknown. Here, the authors find the subarctic North Pacific became stratified during these glaciations due to closure of the Bering Strait, which would have removed CO2 from the atmosphere and caused global cooling.
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Pouchon C, Fernández A, Nassar JM, Boyer F, Aubert S, Lavergne S, Mavárez J. Phylogenomic Analysis of the Explosive Adaptive Radiation of the Espeletia Complex (Asteraceae) in the Tropical Andes. Syst Biol 2018; 67:1041-1060. [PMID: 30339252 DOI: 10.1093/sysbio/syy022] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 03/15/2018] [Indexed: 01/17/2023] Open
Abstract
The subtribe Espeletiinae (Asteraceae), endemic to the high-elevations in the Northern Andes, exhibits an exceptional diversity of species, growth-forms, and reproductive strategies. This complex of 140 species includes large trees, dichotomous trees, shrubs and the extraordinary giant caulescent rosettes, considered as a classic example of adaptation in tropical high-elevation ecosystems. The subtribe has also long been recognized as a prominent case of adaptive radiation, but the understanding of its evolution has been hampered by a lack of phylogenetic resolution. Herein, we produce the first fully resolved phylogeny of all morphological groups of Espeletiinae, using whole plastomes and about a million nuclear nucleotides obtained with an original de novo assembly procedure without reference genome, and analyzed with traditional and coalescent-based approaches that consider the possible impact of incomplete lineage sorting and hybridization on phylogenetic inference. We show that the diversification of Espeletiinae started from a rosette ancestor about 2.3 Ma, after the final uplift of the Northern Andes. This was followed by two independent radiations in the Colombian and Venezuelan Andes, with a few trans-cordilleran dispersal events among low-elevation tree lineages but none among high-elevation rosettes. We demonstrate complex scenarios of morphological change in Espeletiinae, usually implying the convergent evolution of growth-forms with frequent loss/gains of various traits. For instance, caulescent rosettes evolved independently in both countries, likely as convergent adaptations to life in tropical high-elevation habitats. Tree growth-forms evolved independently three times from the repeated colonization of lower elevations by high-elevation rosette ancestors. The rate of morphological diversification increased during the early phase of the radiation, after which it decreased steadily towards the present. On the other hand, the rate of species diversification in the best-sampled Venezuelan radiation was on average very high (3.1 spp/My), with significant rate variation among growth-forms (much higher in polycarpic caulescent rosettes). Our results point out a scenario where both adaptive morphological evolution and geographical isolation due to Pleistocene climatic oscillations triggered an exceptionally rapid radiation for a continental plant group.
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Affiliation(s)
- Charles Pouchon
- Laboratoire d'Ecologie Alpine, UMR 5553, Université Grenoble Alpes-CNRS, Grenoble, France
| | - Angel Fernández
- Herbario IVIC, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, Apartado 20632, Caracas 1020-A, Venezuela
| | - Jafet M Nassar
- Laboratorio de Biología de Organismos, Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apartado 20632, Caracas 1020-A, Venezuela
| | - Frédéric Boyer
- Laboratoire d'Ecologie Alpine, UMR 5553, Université Grenoble Alpes-CNRS, Grenoble, France
| | - Serge Aubert
- Laboratoire d'Ecologie Alpine, UMR 5553, Université Grenoble Alpes-CNRS, Grenoble, France.,Station alpine Joseph-Fourier, UMS 3370, Université Grenoble Alpes-CNRS, Grenoble, France
| | - Sébastien Lavergne
- Laboratoire d'Ecologie Alpine, UMR 5553, Université Grenoble Alpes-CNRS, Grenoble, France
| | - Jesús Mavárez
- Laboratoire d'Ecologie Alpine, UMR 5553, Université Grenoble Alpes-CNRS, Grenoble, France
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Dyez KA, Hönisch B, Schmidt GA. Early Pleistocene obliquity-scale pCO 2 variability at ~1.5 million years ago. PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY 2018; 33:1270-1291. [PMID: 32715282 PMCID: PMC7380090 DOI: 10.1029/2018pa003349] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 10/31/2018] [Indexed: 05/12/2023]
Abstract
In the early Pleistocene, global temperature cycles predominantly varied with ~41-kyr (obliquity-scale) periodicity. Atmospheric greenhouse gas concentrations likely played a role in these climate cycles; marine sediments provide an indirect geochemical means to estimate early Pleistocene CO2. Here we present a boron isotope-based record of continuous high-resolution surface ocean pH and inferred atmospheric CO2 changes. Our results show that, within a window of time in the early Pleistocene (1.38-1.54 Ma), pCO2 varied with obliquity, confirming that, analogous to late Pleistocene conditions, the carbon cycle and climate covaried at ~1.5 Ma. Pairing the reconstructed early Pleistocene pCO2 amplitude (92 ±13 μatm) with a comparably smaller global surface temperature glacial/interglacial amplitude (3.0 ±0.5 K), yields a surface temperature change to CO2 radiative forcing ratio of S [CO2]~0.75 (± 0.5) °C/Wm-2, as compared to the late Pleistocene S [CO2] value of ~1.75 (± 0.6) °C/Wm-2. This direct comparison of pCO2 and temperature implicitly incorporates the large ice sheet forcing as an internal feedback and is not directly applicable to future warming. We evaluate this result with a simple climate model, and show that the presumably thinner, though extensive, northern hemisphere ice sheets would increase surface temperature sensitivity to radiative forcing. Thus, the mechanism to dampen actual temperature variability in the early Pleistocene more likely lies with Southern Ocean circulation dynamics or antiphase hemispheric forcing. We also compile this new carbon dioxide record with published Plio-Pleistocene δ11B records using consistent boundary conditions and explore potential reasons for the discrepancy between Pliocene pCO2 based on different planktic foraminifera.
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Affiliation(s)
- Kelsey A. Dyez
- Lamont-Doherty Earth Observatory, Columbia University, New York, NY, USA
- Now at Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Bärbel Hönisch
- Lamont-Doherty Earth Observatory, Columbia University, New York, NY, USA
- Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
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Novel biomineralization strategy in calcareous foraminifera. Sci Rep 2018; 8:10201. [PMID: 29976938 PMCID: PMC6033919 DOI: 10.1038/s41598-018-28400-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 06/21/2018] [Indexed: 11/08/2022] Open
Abstract
This work shows that calcareous benthic foraminifera are capable of agglutinating sedimentary particles also. In particular, we focus on Melonis barleeanus. Traditionally considered a calcareous species, our data revealed the presence of minute (~3 μm) sedimentary particles (silicate grains) inside the chamber walls of the examined shells. These particles were arranged in a definitive and systematic pattern, and the similar grain chemical characterization and size suggested a relatively high degree of selectivity in both modern and fossil specimens. Based on these results, we propose that M. barleeanus is capable of agglutinating sedimentary particles during the formation of a new chamber. The analysis of other calcareous foraminiferal species (e.g., Cassidulina neoteretis, Lobatula lobatula, Nonionella stella) did not reveal the presence of silicate grains in the shell of the specimens analyzed confirming this to be a characteristic of M. barleeanus. Considering that the isotopic and chemical composition of this species is widely used in paleoclimatic and paleoceanographic reconstructions, we used a mixing model to better constrain the influence of sedimentary particles on M. barleeanus δ18O data. Our model showed that the calcite δ18O would increase by ~0.9-2‰ if 10 wt% of feldspars (i.e., anorthite, albite, orthoclase) and quartz, respectively, were included in the analyzed shell. Based on these results, we emphasize that it is of paramount importance to consider M. barleeanus unusual biomineralization strategy during the interpretation of geological records and to investigate the presence of similar processes in other calcareous foraminiferal species.
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36
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Surface ocean pH variations since 1689 CE and recent ocean acidification in the tropical South Pacific. Nat Commun 2018; 9:2543. [PMID: 29959313 PMCID: PMC6026204 DOI: 10.1038/s41467-018-04922-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 05/18/2018] [Indexed: 11/23/2022] Open
Abstract
Increasing atmospheric CO2 from man-made climate change is reducing surface ocean pH. Due to limited instrumental measurements and historical pH records in the world’s oceans, seawater pH variability at the decadal and centennial scale remains largely unknown and requires documentation. Here we present evidence of striking secular trends of decreasing pH since the late nineteenth century with pronounced interannual to decadal–interdecadal pH variability in the South Pacific Ocean from 1689 to 2011 CE. High-amplitude oceanic pH changes, likely related to atmospheric CO2 uptake and seawater dissolved inorganic carbon fluctuations, reveal a coupled relationship to sea surface temperature variations and highlight the marked influence of El Niño/Southern Oscillation and Interdecadal Pacific Oscillation. We suggest changing surface winds strength and zonal advection processes as the main drivers responsible for regional pH variability up to 1881 CE, followed by the prominent role of anthropogenic CO2 in accelerating the process of ocean acidification. Ocean acidification due to the industrial era is a major marine environmental concern, yet little is known on the historical ocean pH changes prior to human influence. Here, Wu et al. show that tropical South Pacific seawater pH is linked to ENSO pacing and has recently been decreasing rapidly.
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37
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The palaeoecological context of the Oldowan–Acheulean in southern Africa. Nat Ecol Evol 2018; 2:1080-1086. [DOI: 10.1038/s41559-018-0560-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 04/18/2018] [Indexed: 11/08/2022]
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Gu X, Li K, Pang K, Ma Y, Wang X. Effects of pH on the growth and NH 4-N uptake of Skeletonema costatum and Nitzschia closterium. MARINE POLLUTION BULLETIN 2017; 124:946-952. [PMID: 28162247 DOI: 10.1016/j.marpolbul.2017.01.048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 01/20/2017] [Accepted: 01/24/2017] [Indexed: 06/06/2023]
Abstract
Ocean acidification (OA) and eutrophication intensifies in coastal sea under anthropogenic impact. OA coupled with the NH4-N source effect in coastal water is likely to affect the planktonic ecosystem. In this work, Skeletonema costatum and Nitzschia closterium were chosen as typical species of diatom in Chinese coastal ecosystems to test the potential effect of OA and NH4-N. Results showed that the growth and NH4-N uptake of S. costatum and N. closterium were significantly inhibited by pH decline. The maximum uptake rate is higher than the maximum growth rate, implying that NH4-N was assimilated faster for S. costatum and N. closterium with decreasing pH. Therefore, the inhibition rate of the growth of the two diatoms by the coupling effect of OA and eutrophication (pH7.45) is higher that than in the coastal sea by the end of the 21st century (pH7.71).
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Affiliation(s)
- Xingyan Gu
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Keqiang Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China.
| | - Kai Pang
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Yunpeng Ma
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Xiulin Wang
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
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Abstract
Conflicting sets of hypotheses highlight either the role of ice sheets or atmospheric carbon dioxide (CO2) in causing the increase in duration and severity of ice age cycles ∼1 Mya during the Mid-Pleistocene Transition (MPT). We document early MPT CO2 cycles that were smaller than during recent ice age cycles. Using model simulations, we attribute this to post-MPT increase in glacial-stage dustiness and its effect on Southern Ocean productivity. Detailed analysis reveals the importance of CO2 climate forcing as a powerful positive feedback that magnified MPT climate change originally triggered by a change in ice sheet dynamics. These findings offer insights into the close coupling of climate, oceans, and ice sheets within the Earth System. During the Mid-Pleistocene Transition (MPT; 1,200–800 kya), Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40,000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical. Testing hypotheses that implicate changing atmospheric CO2 levels as a driver of the MPT has proven difficult with available observations. Here, we use orbitally resolved, boron isotope CO2 data to show that the glacial to interglacial CO2 difference increased from ∼43 to ∼75 μatm across the MPT, mainly because of lower glacial CO2 levels. Through carbon cycle modeling, we attribute this decline primarily to the initiation of substantive dust-borne iron fertilization of the Southern Ocean during peak glacial stages. We also observe a twofold steepening of the relationship between sea level and CO2-related climate forcing that is suggestive of a change in the dynamics that govern ice sheet stability, such as that expected from the removal of subglacial regolith or interhemispheric ice sheet phase-locking. We argue that neither ice sheet dynamics nor CO2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets.
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Pack A, Höweling A, Hezel DC, Stefanak MT, Beck AK, Peters STM, Sengupta S, Herwartz D, Folco L. Tracing the oxygen isotope composition of the upper Earth's atmosphere using cosmic spherules. Nat Commun 2017; 8:15702. [PMID: 28569769 PMCID: PMC5461487 DOI: 10.1038/ncomms15702] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 04/21/2017] [Indexed: 11/30/2022] Open
Abstract
Molten I-type cosmic spherules formed by heating, oxidation and melting of extraterrestrial Fe,Ni metal alloys. The entire oxygen in these spherules sources from the atmosphere. Therefore, I-type cosmic spherules are suitable tracers for the isotopic composition of the upper atmosphere at altitudes between 80 and 115 km. Here we present data on I-type cosmic spherules collected in Antarctica. Their composition is compared with the composition of tropospheric O2. Our data suggest that the Earth's atmospheric O2 is isotopically homogenous up to the thermosphere. This makes fossil I-type micrometeorites ideal proxies for ancient atmospheric CO2 levels.
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Affiliation(s)
- Andreas Pack
- Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstraße 1, 37077 Göttingen, Germany
| | - Andres Höweling
- Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstraße 1, 37077 Göttingen, Germany
- Karlsruher Institut für Technologie, Institut für Angewandte Materialien - Werkstoffprozesstechnik, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Dominik C. Hezel
- Universität Köln, Institut für Geologie und Mineralogie, Greinstraße 4-6, 50939 Köln, Germany
| | - Maren T. Stefanak
- Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstraße 1, 37077 Göttingen, Germany
| | - Anne-Katrin Beck
- Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstraße 1, 37077 Göttingen, Germany
| | - Stefan T. M. Peters
- Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstraße 1, 37077 Göttingen, Germany
| | - Sukanya Sengupta
- Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstraße 1, 37077 Göttingen, Germany
| | - Daniel Herwartz
- Universität Köln, Institut für Geologie und Mineralogie, Greinstraße 4-6, 50939 Köln, Germany
| | - Luigi Folco
- Universitá di Pisa, Dipartimento di Scienze della Terra, Via Santa Maria 53, 56126 Pisa, Italy
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Episodic release of CO 2 from the high-latitude North Atlantic Ocean during the last 135 kyr. Nat Commun 2017; 8:14498. [PMID: 28224985 PMCID: PMC5322501 DOI: 10.1038/ncomms14498] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 01/06/2017] [Indexed: 11/21/2022] Open
Abstract
Antarctic ice cores document glacial-interglacial and millennial-scale variability in atmospheric pCO2 over the past 800 kyr. The ocean, as the largest active carbon reservoir on this timescale, is thought to have played a dominant role in these pCO2 fluctuations, but it remains unclear how and where in the ocean CO2 was stored during glaciations and released during (de)glacial millennial-scale climate events. The evolution of surface ocean pCO2 in key locations can therefore provide important clues for understanding the ocean's role in Pleistocene carbon cycling. Here we present a 135-kyr record of shallow subsurface pCO2 and nutrient levels from the Norwegian Sea, an area of intense CO2 uptake from the atmosphere today. Our results suggest that the Norwegian Sea probably acted as a CO2 source towards the end of Heinrich stadials HS1, HS4 and HS11, and may have contributed to the increase in atmospheric pCO2 at these times. Glacial-interglacial variations in atmospheric pCO2 remain unexplained. Here, the authors show that the Norwegian Sea, an modern area of intense CO2 uptake, acted as a CO2 source during the terminations of Heinrich stadials 1, 4 and 11, sometimes characterized by rapid increases in atmospheric pCO2.
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Evolution of global temperature over the past two million years. Nature 2016; 538:226-228. [DOI: 10.1038/nature19798] [Citation(s) in RCA: 157] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 08/24/2016] [Indexed: 11/08/2022]
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Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate. Nature 2016; 533:380-4. [PMID: 27111509 DOI: 10.1038/nature17423] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 02/10/2016] [Indexed: 11/08/2022]
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Bolton CT, Hernández-Sánchez MT, Fuertes MÁ, González-Lemos S, Abrevaya L, Mendez-Vicente A, Flores JA, Probert I, Giosan L, Johnson J, Stoll HM. Decrease in coccolithophore calcification and CO2 since the middle Miocene. Nat Commun 2016; 7:10284. [PMID: 26762469 PMCID: PMC4735581 DOI: 10.1038/ncomms10284] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 11/26/2015] [Indexed: 12/11/2022] Open
Abstract
Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone ɛp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity.
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Affiliation(s)
- Clara T. Bolton
- Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain
- Aix-Marseille University, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France
| | | | - Miguel-Ángel Fuertes
- Grupo de Geociencias Oceánicas, Geology Department, University of Salamanca, Salamanca 37008, Spain
| | - Saúl González-Lemos
- Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain
| | - Lorena Abrevaya
- Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain
| | - Ana Mendez-Vicente
- Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain
| | - José-Abel Flores
- Grupo de Geociencias Oceánicas, Geology Department, University of Salamanca, Salamanca 37008, Spain
| | - Ian Probert
- CNRS, Sorbonne Universités-Université Pierre et Marie Curie (UPMC) Paris 06, FR2424, Roscoff Culture Collection, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France
| | - Liviu Giosan
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 266 Woods Hole Road, MS# 22, Woods Hole, Massachusetts 02543-1050, USA
| | - Joel Johnson
- University of New Hampshire, Department of Earth Sciences, 56 College Road, James Hall, Durham, New Hampshire 03824-3589, USA
| | - Heather M. Stoll
- Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain
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Does plant size affect growth responses to water availability at glacial, modern and future CO2 concentrations? Ecol Res 2016. [DOI: 10.1007/s11284-015-1330-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Hernández-Delgado EA. The emerging threats of climate change on tropical coastal ecosystem services, public health, local economies and livelihood sustainability of small islands: Cumulative impacts and synergies. MARINE POLLUTION BULLETIN 2015; 101:5-28. [PMID: 26455783 DOI: 10.1016/j.marpolbul.2015.09.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/08/2015] [Accepted: 09/15/2015] [Indexed: 06/05/2023]
Abstract
Climate change has significantly impacted tropical ecosystems critical for sustaining local economies and community livelihoods at global scales. Coastal ecosystems have largely declined, threatening the principal source of protein, building materials, tourism-based revenue, and the first line of defense against storm swells and sea level rise (SLR) for small tropical islands. Climate change has also impacted public health (i.e., altered distribution and increased prevalence of allergies, water-borne, and vector-borne diseases). Rapid human population growth has exacerbated pressure over coupled social-ecological systems, with concomitant non-sustainable impacts on natural resources, water availability, food security and sovereignty, public health, and quality of life, which should increase vulnerability and erode adaptation and mitigation capacity. This paper examines cumulative and synergistic impacts of climate change in the challenging context of highly vulnerable small tropical islands. Multiple adaptive strategies of coupled social-ecological ecosystems are discussed. Multi-level, multi-sectorial responses are necessary for adaptation to be successful.
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Affiliation(s)
- E A Hernández-Delgado
- University of Puerto Rico, Center for Applied Tropical Ecology and Conservation, Coral Reef Research Group, PO Box 23360, San Juan 00931-3360, Puerto Rico; University of Puerto Rico, Department of Biology, PO Box 23360, San Juan 00931-3360, Puerto Rico.
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Temme AA, Liu JC, Cornwell WK, Cornelissen JHC, Aerts R. Winners always win: growth of a wide range of plant species from low to future high CO2. Ecol Evol 2015; 5:4949-61. [PMID: 26640673 PMCID: PMC4662314 DOI: 10.1002/ece3.1687] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 06/16/2015] [Accepted: 07/09/2015] [Indexed: 02/06/2023] Open
Abstract
Evolutionary adaptation to variation in resource supply has resulted in plant strategies that are based on trade-offs in functional traits. Here, we investigate, for the first time across multiple species, whether such trade-offs are also apparent in growth and morphology responses to past low, current ambient, and future high CO 2 concentrations. We grew freshly germinated seedlings of up to 28 C3 species (16 forbs, 6 woody, and 6 grasses) in climate chambers at 160 ppm, 450 ppm, and 750 ppm CO 2. We determined biomass, allocation, SLA (specific leaf area), LAR (leaf area ratio), and RGR (relative growth rate), thereby doubling the available data on these plant responses to low CO 2. High CO 2 increased RGR by 8%; low CO 2 decreased RGR by 23%. Fast growers at ambient CO 2 had the greatest reduction in RGR at low CO 2 as they lost the benefits of a fast-growth morphology (decoupling of RGR and LAR [leaf area ratio]). Despite these shifts species ranking on biomass and RGR was unaffected by CO 2, winners continued to win, regardless of CO 2. Unlike for other plant resources we found no trade-offs in morphological and growth responses to CO 2 variation, changes in morphological traits were unrelated to changes in growth at low or high CO 2. Thus, changes in physiology may be more important than morphological changes in response to CO 2 variation.
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Affiliation(s)
- Andries A. Temme
- Department of Ecological ScienceVU UniversityDe Boelelaan 10851081HVAmsterdamThe Netherlands
| | - Jin Chun Liu
- Department of Ecological ScienceVU UniversityDe Boelelaan 10851081HVAmsterdamThe Netherlands
- Key Laboratory of Eco‐Environment in Three Gorges Reservoir RegionSchool of Life ScienceSouthwest UniversityBeibeiChongqing400715China
| | - William K. Cornwell
- Department of Ecological ScienceVU UniversityDe Boelelaan 10851081HVAmsterdamThe Netherlands
- Ecology and Evolution Research CentreSchool of Biological, Earth, and Environmental SciencesUniversity of New South WalesKensington 2052SydneyNew South WalesAustralia
| | | | - Rien Aerts
- Department of Ecological ScienceVU UniversityDe Boelelaan 10851081HVAmsterdamThe Netherlands
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Atmospheric composition 1 million years ago from blue ice in the Allan Hills, Antarctica. Proc Natl Acad Sci U S A 2015; 112:6887-91. [PMID: 25964367 DOI: 10.1073/pnas.1420232112] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Here, we present direct measurements of atmospheric composition and Antarctic climate from the mid-Pleistocene (∼1 Ma) from ice cores drilled in the Allan Hills blue ice area, Antarctica. The 1-Ma ice is dated from the deficit in (40)Ar relative to the modern atmosphere and is present as a stratigraphically disturbed 12-m section at the base of a 126-m ice core. The 1-Ma ice appears to represent most of the amplitude of contemporaneous climate cycles and CO2 and CH4 concentrations in the ice range from 221 to 277 ppm and 411 to 569 parts per billion (ppb), respectively. These concentrations, together with measured δD of the ice, are at the warm end of the field for glacial-interglacial cycles of the last 800 ky and span only about one-half of the range. The highest CO2 values in the 1-Ma ice fall within the range of interglacial values of the last 400 ka but are up to 7 ppm higher than any interglacial values between 450 and 800 ka. The lowest CO2 values are 30 ppm higher than during any glacial period between 450 and 800 ka. This study shows that the coupling of Antarctic temperature and atmospheric CO2 extended into the mid-Pleistocene and demonstrates the feasibility of discontinuously extending the current ice core record beyond 800 ka by shallow coring in Antarctic blue ice areas.
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50
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Martínez-Botí MA, Foster GL, Chalk TB, Rohling EJ, Sexton PF, Lunt DJ, Pancost RD, Badger MPS, Schmidt DN. Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records. Nature 2015; 518:49-54. [PMID: 25652996 DOI: 10.1038/nature14145] [Citation(s) in RCA: 233] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 12/05/2014] [Indexed: 11/09/2022]
Abstract
Theory and climate modelling suggest that the sensitivity of Earth's climate to changes in radiative forcing could depend on the background climate. However, palaeoclimate data have thus far been insufficient to provide a conclusive test of this prediction. Here we present atmospheric carbon dioxide (CO2) reconstructions based on multi-site boron-isotope records from the late Pliocene epoch (3.3 to 2.3 million years ago). We find that Earth's climate sensitivity to CO2-based radiative forcing (Earth system sensitivity) was half as strong during the warm Pliocene as during the cold late Pleistocene epoch (0.8 to 0.01 million years ago). We attribute this difference to the radiative impacts of continental ice-volume changes (the ice-albedo feedback) during the late Pleistocene, because equilibrium climate sensitivity is identical for the two intervals when we account for such impacts using sea-level reconstructions. We conclude that, on a global scale, no unexpected climate feedbacks operated during the warm Pliocene, and that predictions of equilibrium climate sensitivity (excluding long-term ice-albedo feedbacks) for our Pliocene-like future (with CO2 levels up to maximum Pliocene levels of 450 parts per million) are well described by the currently accepted range of an increase of 1.5 K to 4.5 K per doubling of CO2.
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Affiliation(s)
- M A Martínez-Botí
- Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK
| | - G L Foster
- Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK
| | - T B Chalk
- Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK
| | - E J Rohling
- 1] Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK [2] Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - P F Sexton
- Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes, MK7 6AA, UK
| | - D J Lunt
- 1] School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK [2] The Cabot Institute, University of Bristol, Bristol BS8 1UJ, UK
| | - R D Pancost
- 1] The Cabot Institute, University of Bristol, Bristol BS8 1UJ, UK [2] Organic Geochemistry Unit, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | - M P S Badger
- 1] The Cabot Institute, University of Bristol, Bristol BS8 1UJ, UK [2] Organic Geochemistry Unit, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | - D N Schmidt
- 1] The Cabot Institute, University of Bristol, Bristol BS8 1UJ, UK [2] School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ, UK
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