1
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Hutchinson DK, Menviel L, Meissner KJ, Hogg AM. East Antarctic warming forced by ice loss during the Last Interglacial. Nat Commun 2024; 15:1026. [PMID: 38310088 PMCID: PMC10838265 DOI: 10.1038/s41467-024-45501-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 01/26/2024] [Indexed: 02/05/2024] Open
Abstract
During the Last Interglacial (LIG; 129-116 thousand years before present), the Antarctic ice sheet (AIS) was 1 to 7 m sea level equivalent smaller than at pre-industrial. Here, we assess the climatic impact of partial AIS melting at the LIG by forcing a coupled climate model with a smaller AIS and the equivalent meltwater input around the Antarctic coast. We find that changes in surface elevation induce surface warming over East Antarctica of 2 to 4 °C, and sea surface temperature (SST) increases in the Weddell and Ross Seas by up to 2 °C. Meltwater forcing causes a high latitude SST decrease and a subsurface (100-500 m) ocean temperature increase by up to 2 °C in the Ross Sea. Our results suggest that the combination of a smaller AIS and enhanced meltwater input leads to a larger sub-surface warming than meltwater alone and induces further Antarctic warming than each perturbation separately.
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Affiliation(s)
- David K Hutchinson
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia.
- The Australian Centre for Excellence in Antarctic Science, University of New South Wales, Sydney, NSW, Australia.
| | - Laurie Menviel
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
- The Australian Centre for Excellence in Antarctic Science, University of New South Wales, Sydney, NSW, Australia
| | - Katrin J Meissner
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
| | - Andrew McC Hogg
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
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2
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Li T, Robinson LF, MacGilchrist GA, Chen T, Stewart JA, Burke A, Wang M, Li G, Chen J, Rae JWB. Enhanced subglacial discharge from Antarctica during meltwater pulse 1A. Nat Commun 2023; 14:7327. [PMID: 37957152 PMCID: PMC10643554 DOI: 10.1038/s41467-023-42974-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023] Open
Abstract
Subglacial discharge from the Antarctic Ice Sheet (AIS) likely played a crucial role in the loss of the ice sheet and the subsequent rise in sea level during the last deglaciation. However, no direct proxy is currently available to document subglacial discharge from the AIS, which leaves significant gaps in our understanding of the complex interactions between subglacial discharge and ice-sheet stability. Here we present deep-sea coral 234U/238U records from the Drake Passage in the Southern Ocean to track subglacial discharge from the AIS. Our findings reveal distinctively higher seawater 234U/238U values from 15,400 to 14,000 years ago, corresponding to the period of the highest iceberg-rafted debris flux and the occurrence of the meltwater pulse 1A event. This correlation suggests a causal link between enhanced subglacial discharge, synchronous retreat of the AIS, and the rapid rise in sea levels. The enhanced subglacial discharge and subsequent AIS retreat appear to have been preconditioned by a stronger and warmer Circumpolar Deep Water, thus underscoring the critical role of oceanic heat in driving major ice-sheet retreat.
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Affiliation(s)
- Tao Li
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.
- School of Earth Sciences, University of Bristol, Bristol, UK.
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China.
| | - Laura F Robinson
- School of Earth Sciences, University of Bristol, Bristol, UK
- Department of Environment and Geography, University of York, York, UK
| | - Graeme A MacGilchrist
- Program in Atmospheric and Oceanic Science, Princeton University, Princeton, NJ, USA
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Tianyu Chen
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | | | - Andrea Burke
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Maoyu Wang
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - Gaojun Li
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - Jun Chen
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - James W B Rae
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
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3
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Vanderstraeten A, Mattielli N, Laruelle GG, Gili S, Bory A, Gabrielli P, Boxho S, Tison JL, Bonneville S. Identifying the provenance and quantifying the contribution of dust sources in EPICA Dronning Maud Land ice core (Antarctica) over the last deglaciation (7-27 kyr BP): A high-resolution, quantitative record from a new Rare Earth Element mixing model. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 881:163450. [PMID: 37061058 DOI: 10.1016/j.scitotenv.2023.163450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 04/07/2023] [Accepted: 04/07/2023] [Indexed: 06/01/2023]
Abstract
Antarctic ice cores have revealed the interplay between dust and climate in the Southern Hemisphere. Yet, so far, no continuous record of dust provenance has been established through the last deglaciation. Here, using a new database of 207 Rare Earth Element (REE) patterns measured in dust and sediments/soils from well-known potential source areas (PSA) of the Southern Hemisphere, we developed a statistical model combining those inputs to provide the best fit to the REE patterns measured in EPICA Dronning Maud Land (EDML) ice core (E. Antarctica). Out of 398 samples measured in the EDML core, 386 samples have been un-mixed with statistical significance. Combined with the total atmospheric deposition, we quantified the dust flux from each PSA to EDML between 7 and 27 kyr BP. Our results reveal that the dust composition was relatively uniform up until 14.5 kyr BP despite a large drop in atmospheric deposition at ∼18 kyr with a large contribution from Patagonia yielding ∼68 % of total dust deposition. The remaining dust was supplied from Australia (14-15 %), Southern Africa (∼9 %), New Zealand (∼3-4 %) and Puna-Altiplano (∼2-3 %). The most striking change occurred ∼14.5 kyr BP when Patagonia dropped below 50 % on average while low-latitude PSA increased their contributions to 21-23 % for Southern Africa, 13-21 % for Australia and ∼ 4-10 % for Puna-Altiplano. We argue that this shift is linked to long-lasting changes in the hydrology of Patagonian rivers and to sudden acceleration of the submersion of Patagonian shelf at 14.5 kyr BP, highlighting a relationship between dust composition and eustatic sea level. Early Holocene dust composition is highly variable, with Patagonian contribution being still prevalent, at ∼50 % on average. Provided a good coverage of local and distal PSA, our statistical model based on REE pattern offers a straightforward and cost-effective method to trace dust source in ice cores.
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Affiliation(s)
- Aubry Vanderstraeten
- Laboratoire G-Time, Département Géosciences, Environnement et Société (DGES), Université Libre de Bruxelles (ULB), Av. F. Roosevelt, 50 (CP 160/02), Brussels 1050, Belgium; Laboratoire d'Océanologie et de Géosciences UMR 8187-LOG, Univ. Lille, CNRS, Univ. Littoral Côte d'Opale, IRD, F-59000 Lille, France
| | - Nadine Mattielli
- Laboratoire G-Time, Département Géosciences, Environnement et Société (DGES), Université Libre de Bruxelles (ULB), Av. F. Roosevelt, 50 (CP 160/02), Brussels 1050, Belgium
| | - Goulven G Laruelle
- Biogéochimie et Modélisation du Système Terre, Département Géosciences, Environnement et Société (DGES), Université Libre de Bruxelles (ULB), Brussels 1050, Belgium
| | - Stefania Gili
- Department of Geosciences, Princeton University, Princeton, NJ 08544, United States of America
| | - Aloys Bory
- Laboratoire d'Océanologie et de Géosciences UMR 8187-LOG, Univ. Lille, CNRS, Univ. Littoral Côte d'Opale, IRD, F-59000 Lille, France
| | - Paolo Gabrielli
- Italian Glaciological Committee, c/o University of Turin, Turin, Italy
| | - Sibylle Boxho
- Laboratoire G-Time, Département Géosciences, Environnement et Société (DGES), Université Libre de Bruxelles (ULB), Av. F. Roosevelt, 50 (CP 160/02), Brussels 1050, Belgium
| | - Jean-Louis Tison
- Laboratoire de Glaciologie, Département Géosciences, Environnement et Société (DGES), Université Libre de Bruxelles (ULB), Av. F. Roosevelt, 50 (CP 160/02), Brussels 1050, Belgium
| | - Steeve Bonneville
- Biogéochimie et Modélisation du Système Terre, Département Géosciences, Environnement et Société (DGES), Université Libre de Bruxelles (ULB), Brussels 1050, Belgium.
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4
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Yi L, Medina-Elizalde M, Tan L, Kemp DB, Li Y, Kletetschka G, Xie Q, Yao H, He H, Deng C, Ogg JG. Plio-Pleistocene deep-sea ventilation in the eastern Pacific and potential linkages with Northern Hemisphere glaciation. SCIENCE ADVANCES 2023; 9:eadd1467. [PMID: 36827375 PMCID: PMC9956117 DOI: 10.1126/sciadv.add1467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 01/25/2023] [Indexed: 06/18/2023]
Abstract
Antarctic bottom water (AABW) production is a key factor governing global ocean circulation, and the present disintegration of the Antarctic Ice Sheet slows it. However, its long-term variability has not been well documented. On the basis of high-resolution chemical scanning of a well-dated marine ferromanganese nodule from the eastern Pacific, we derive a record of abyssal ventilation spanning the past 4.7 million years and evaluate its linkage to AABW formation over this period. We find that abyssal ventilation was relatively weak in the early Pliocene and persistently intensified from 3.4 million years ago onward. Seven episodes of markedly reduced ocean ventilation indicative of AABW formation collapse are identified since the late Pliocene, which were accompanied by key stages of Northern Hemisphere glaciation. We suggest that the interpolar climate synchronization within these inferred seven collapse events may have intensified global glaciation by inducing poleward moisture transport in the Northern Hemisphere.
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Affiliation(s)
- Liang Yi
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
| | | | - Liangcheng Tan
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, China
- Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, China
| | - David B. Kemp
- State Key Laboratory for Biogeology and Environmental Geology and Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan, China
| | - Yanzhen Li
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, China
- State Key Laboratory for Biogeology and Environmental Geology and Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan, China
| | - Gunther Kletetschka
- Institute of Hydrogeology, Engineering Geology, and Applied Geophysics, Faculty of Science, Charles University, Prague, Czech Republic
- Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA
| | - Qiang Xie
- Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China
| | - Huiqiang Yao
- Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources, Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Huaiyu He
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Chenglong Deng
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - James G. Ogg
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
- State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, China
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5
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Park JY, Schloesser F, Timmermann A, Choudhury D, Lee JY, Nellikkattil AB. Future sea-level projections with a coupled atmosphere-ocean-ice-sheet model. Nat Commun 2023; 14:636. [PMID: 36788205 PMCID: PMC9929224 DOI: 10.1038/s41467-023-36051-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 01/12/2023] [Indexed: 02/16/2023] Open
Abstract
Climate-forced, offline ice-sheet model simulations have been used extensively in assessing how much ice-sheets can contribute to future global sea-level rise. Typically, these model projections do not account for the two-way interactions between ice-sheets and climate. To quantify the impact of ice-ocean-atmosphere feedbacks, here we conduct greenhouse warming simulations with a coupled global climate-ice-sheet model of intermediate complexity. Following the Shared Socioeconomic Pathway (SSP) 1-1.9, 2-4.5, 5-8.5 emission scenarios, the model simulations ice-sheet contributions to global sea-level rise by 2150 of 0.2 ± 0.01, 0.5 ± 0.01 and 1.4 ± 0.1 m, respectively. Antarctic ocean-ice-sheet-ice-shelf interactions enhance future subsurface basal melting, while freshwater-induced atmospheric cooling reduces surface melting and iceberg calving. The combined effect is likely to decelerate global sea-level rise contributions from Antarctica relative to the uncoupled climate-forced ice-sheet model configuration. Our results demonstrate that estimates of future sea-level rise fundamentally depend on the complex interactions between ice-sheets, icebergs, ocean and the atmosphere.
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Affiliation(s)
- Jun-Young Park
- Center for Climate Physics, Institute for Basic Science, Busan, Republic of Korea. .,Department of Climate System, Pusan National University, Busan, Republic of Korea.
| | - Fabian Schloesser
- International Pacific Research Center, University of Hawaii, Honolulu, Hawaii, USA.
| | - Axel Timmermann
- grid.410720.00000 0004 1784 4496Center for Climate Physics, Institute for Basic Science, Busan, Republic of Korea ,grid.262229.f0000 0001 0719 8572Pusan National University, Busan, Republic of Korea
| | - Dipayan Choudhury
- grid.410720.00000 0004 1784 4496Center for Climate Physics, Institute for Basic Science, Busan, Republic of Korea ,grid.1005.40000 0004 4902 0432Climate Change Research Centre, University of New South Wales, Sydney, NSW Australia
| | - June-Yi Lee
- grid.410720.00000 0004 1784 4496Center for Climate Physics, Institute for Basic Science, Busan, Republic of Korea ,grid.262229.f0000 0001 0719 8572Department of Climate System, Pusan National University, Busan, Republic of Korea ,grid.262229.f0000 0001 0719 8572Research Center for Climate Sciences, Pusan National University, Busan, Republic of Korea
| | - Arjun Babu Nellikkattil
- grid.410720.00000 0004 1784 4496Center for Climate Physics, Institute for Basic Science, Busan, Republic of Korea ,grid.262229.f0000 0001 0719 8572Department of Climate System, Pusan National University, Busan, Republic of Korea
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6
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Ancient marine sediment DNA reveals diatom transition in Antarctica. Nat Commun 2022; 13:5787. [PMID: 36184671 PMCID: PMC9527250 DOI: 10.1038/s41467-022-33494-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 09/21/2022] [Indexed: 11/08/2022] Open
Abstract
Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, psbO). We find evidence of warm phases being associated with high relative diatom abundance, and a marked transition from diatoms comprising <10% of all eukaryotes prior to ~14.5 ka, to ~50% after this time, i.e., following Meltwater Pulse 1A, alongside a composition change from sea-ice to open-ocean species. Our study demonstrates that sedaDNA tools can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and paleo-productivity phases throughout multiple glacial-interglacial cycles.
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7
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Subglacial precipitates record Antarctic ice sheet response to late Pleistocene millennial climate cycles. Nat Commun 2022; 13:5428. [PMID: 36109505 PMCID: PMC9477832 DOI: 10.1038/s41467-022-33009-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 08/26/2022] [Indexed: 11/17/2022] Open
Abstract
Ice cores and offshore sedimentary records demonstrate enhanced ice loss along Antarctic coastal margins during millennial-scale warm intervals within the last glacial termination. However, the distal location and short temporal coverage of these records leads to uncertainty in both the spatial footprint of ice loss, and whether millennial-scale ice response occurs outside of glacial terminations. Here we present a >100kyr archive of periodic transitions in subglacial precipitate mineralogy that are synchronous with Late Pleistocene millennial-scale climate cycles. Geochemical and geochronologic data provide evidence for opal formation during cold periods via cryoconcentration of subglacial brine, and calcite formation during warm periods through the addition of subglacial meltwater originating from the ice sheet interior. These freeze-flush cycles represent cyclic changes in subglacial hydrologic-connectivity driven by ice sheet velocity fluctuations. Our findings imply that oscillating Southern Ocean temperatures drive a dynamic response in the Antarctic ice sheet on millennial timescales, regardless of the background climate state. Piccione et al find evidence for Antarctic ice sheet instability driven by millennial cycles in Southern Ocean temperature, providing clues for the mechanisms that link climate change and rapid Antarctic ice loss events.
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8
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Stokes CR, Abram NJ, Bentley MJ, Edwards TL, England MH, Foppert A, Jamieson SSR, Jones RS, King MA, Lenaerts JTM, Medley B, Miles BWJ, Paxman GJG, Ritz C, van de Flierdt T, Whitehouse PL. Response of the East Antarctic Ice Sheet to past and future climate change. Nature 2022; 608:275-286. [PMID: 35948707 DOI: 10.1038/s41586-022-04946-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/07/2022] [Indexed: 11/09/2022]
Abstract
The East Antarctic Ice Sheet contains the vast majority of Earth's glacier ice (about 52 metres sea-level equivalent), but is often viewed as less vulnerable to global warming than the West Antarctic or Greenland ice sheets. However, some regions of the East Antarctic Ice Sheet have lost mass over recent decades, prompting the need to re-evaluate its sensitivity to climate change. Here we review the response of the East Antarctic Ice Sheet to past warm periods, synthesize current observations of change and evaluate future projections. Some marine-based catchments that underwent notable mass loss during past warm periods are losing mass at present but most projections indicate increased accumulation across the East Antarctic Ice Sheet over the twenty-first century, keeping the ice sheet broadly in balance. Beyond 2100, high-emissions scenarios generate increased ice discharge and potentially several metres of sea-level rise within just a few centuries, but substantial mass loss could be averted if the Paris Agreement to limit warming below 2 degrees Celsius is satisfied.
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Affiliation(s)
| | - Nerilie J Abram
- Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory, Australia.,Australian Centre for Excellence in Antarctic Science, Australian National University, Canberra, Australian Capital Territory, Australia
| | | | | | - Matthew H England
- Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia.,Australian Centre for Excellence in Antarctic Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Annie Foppert
- Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | | | - Richard S Jones
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia.,Securing Antarctica's Environmental Future, Monash University, Clayton, Victoria, Australia
| | - Matt A King
- School of Geography, Planning, and Spatial Sciences, University of Tasmania, Hobart, Tasmania, Australia.,Australian Centre for Excellence in Antarctic Science, University of Tasmania, Hobart, Tasmania, Australia
| | - Jan T M Lenaerts
- Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA
| | - Brooke Medley
- Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | - Guy J G Paxman
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | - Catherine Ritz
- Institut des Géosciences de l'Environnement, Université Grenoble Alpes, Grenoble, France
| | - Tina van de Flierdt
- Department of Earth Science and Engineering, Imperial College London, London, UK
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9
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Bailey I, Hemming S, Reilly BT, Rollinson G, Williams T, Weber ME, Raymo ME, Peck VL, Ronge TA, Brachfeld S, O'Connell S, Tauxe L, Warnock JP, Armbrecht L, Cardillo FG, Du Z, Fauth G, Garcia M, Glueder A, Guitard M, Gutjahr M, Hernández‐Almeida I, Hoem FS, Hwang J, Iizuka M, Kato Y, Kenlee B, Martos YM, Pérez LF, Seki O, Tripathi S, Zheng X. Episodes of Early Pleistocene West Antarctic Ice Sheet Retreat Recorded by Iceberg Alley Sediments. PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY 2022; 37:e2022PA004433. [PMID: 36247355 PMCID: PMC9544630 DOI: 10.1029/2022pa004433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 05/11/2022] [Accepted: 06/08/2022] [Indexed: 06/16/2023]
Abstract
Ice loss in the Southern Hemisphere has been greatest over the past 30 years in West Antarctica. The high sensitivity of this region to climate change has motivated geologists to examine marine sedimentary records for evidence of past episodes of West Antarctic Ice Sheet (WAIS) instability. Sediments accumulating in the Scotia Sea are useful to examine for this purpose because they receive iceberg-rafted debris (IBRD) sourced from the Pacific- and Atlantic-facing sectors of West Antarctica. Here we report on the sedimentology and provenance of the oldest of three cm-scale coarse-grained layers recovered from this sea at International Ocean Discovery Program Site U1538. These layers are preserved in opal-rich sediments deposited ∼1.2 Ma during a relatively warm regional climate. Our microCT-based analysis of the layer's in-situ fabric confirms its ice-rafted origin. We further infer that it is the product of an intense but short-lived episode of IBRD deposition. Based on the petrography of its sand fraction and the Phanerozoic 40Ar/39Ar ages of hornblende and mica it contains, we conclude that the IBRD it contains was likely sourced from the Weddell Sea and/or Amundsen Sea embayment(s) of West Antarctica. We attribute the high concentrations of IBRD in these layers to "dirty" icebergs calved from the WAIS following its retreat inland from its modern grounding line. These layers also sit at the top of a ∼366-m thick Pliocene and early Pleistocene sequence that is much more dropstone-rich than its overlying sediments. We speculate this fact may reflect that WAIS mass-balance was highly dynamic during the ∼41-kyr (inter)glacial world.
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Affiliation(s)
- Ian Bailey
- Camborne School of MinesUniversity of ExeterPenryn CampusCornwallUK
| | - Sidney Hemming
- Lamont‐Doherty Earth ObservatoryColumbia UniversityPalisadesNYUSA
| | - Brendan T. Reilly
- Scripps Institution of OceanographyUniversity of California San DiegoLa JollaCAUSA
| | - Gavyn Rollinson
- Camborne School of MinesUniversity of ExeterPenryn CampusCornwallUK
| | - Trevor Williams
- International Ocean Discovery ProgramTexas AM UniversityCollege StationTXUSA
| | - Michael E. Weber
- Department of Geochemistry and PetrologyInstitute for GeosciencesUniversity of BonnBonnGermany
| | - Maureen E. Raymo
- Lamont‐Doherty Earth ObservatoryColumbia UniversityPalisadesNYUSA
| | | | - Thomas A. Ronge
- Alfred‐Wegener‐Institut Helmholtz‐Zentrum für Polar‐und MeeresforschungBremerhavenGermany
| | | | - Suzanne O'Connell
- Department of Earth and Environmental SciencesWesleyan UniversityMiddletownCTUSA
| | - Lisa Tauxe
- Scripps Institution of OceanographyUniversity of California San DiegoLa JollaCAUSA
| | | | - Linda Armbrecht
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaBattery PointTASAustralia
| | - Fabricio G. Cardillo
- Departmento OceanografiaServicio de Hidrografia NavalMinisterio de DefensaBuenos AiresArgentina
| | - Zhiheng Du
- State Key Laboratory of Cryospheric ScienceNorthwest Institute of Eco‐Environment and ResourcesLanzhouChina
| | - Gerson Fauth
- Geology ProgramUniversity of Vale do Rio dos SinosSão LeopoldoBrazil
| | - Marga Garcia
- Andalusian Institute of Earth Science (CSIC‐UGR)GranadaSpain
- Cádiz Oceanographic Centre (IEO‐CSIC)CádizSpain
| | - Anna Glueder
- College of Earth, Ocean, and Atmospheric SciencesOregon State UniversityCorvallisORUSA
| | - Michelle Guitard
- College of Marine ScienceUniversity of South FloridaSt. PetersburgFLUSA
| | - Marcus Gutjahr
- GEOMARHelmholtz Centre for Ocean ResearchUniversity of KielKielGermany
| | | | - Frida S. Hoem
- Department of Earth Science, Marine Palynology and PaleoceanographyUtrecht UniversityUtrechtThe Netherlands
| | - Ji‐Hwan Hwang
- Earth Environmental SciencesKorea Basic Science InstituteChungbuk CheongjuRepublic of Korea
| | | | - Yuji Kato
- Faculty of Life and Environmental SciencesUniversity of TsukubaTsukubaJapan
| | - Bridget Kenlee
- Department of Earth SciencesUniversity of California RiversideRiversideCAUSA
| | - Yasmina M. Martos
- NASA Goddard Space Flight CenterPlanetary Magnetospheres LaboratoryGreenbeltMDUSA
- Department of AstronomyUniversity of MarylandCollege ParkMDUSA
| | - Lara F. Pérez
- British Antarctic SurveyCambridgeUK
- Department of Marine GeologyGeological Survey of Denmark and GreenlandAarhus University CityAarhusDenmark
| | - Osamu Seki
- Institute of Low Temperature ScienceHokkaido UniversitySapporoJapan
| | - Shubham Tripathi
- Marine Stable Isotope LabNational Centre for Polar and Ocean ResearchMinistry of Earth SciencesVasco Da GamaIndia
| | - Xufeng Zheng
- South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhouChina
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10
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Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years. Nat Commun 2022; 13:2044. [PMID: 35440628 PMCID: PMC9018689 DOI: 10.1038/s41467-022-29642-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 03/25/2022] [Indexed: 11/08/2022] Open
Abstract
The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels.
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11
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A Myth for the Sixth Mass Extinction: Telling Noah’s Story during a Climate Crisis. RELIGIONS 2022. [DOI: 10.3390/rel13030243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Myths are open storylines that invite elaboration and modification. The flood narrative of Genesis 6–9, for example, has been readily employed to motivate endangered species protection and to reflect on the rising seas and mass extinctions associated with climate change. The distinctive features of any retelling of the Noah’s ark story reflect the needs of historically situated and culturally embedded audiences. This paper focuses on four versions of Noah’s story: in Genesis, in the Qur’an, at Ark Encounter theme park, and in Darren Aronofsky’s film Noah. Analysis identifies the narrative choices that align each telling with its cultural context and draws out insights for adapting the story for the contemporary climate crisis. A conclusion addresses issues of race and racial injustice in traditional interpretations of Noah’s story, and highlights approaches to redress those inequities in new imaginings of the flood narrative.
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12
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Obase T, Abe-Ouchi A, Saito F. Abrupt climate changes in the last two deglaciations simulated with different Northern ice sheet discharge and insolation. Sci Rep 2021; 11:22359. [PMID: 34824287 PMCID: PMC8616927 DOI: 10.1038/s41598-021-01651-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 10/21/2021] [Indexed: 11/09/2022] Open
Abstract
There were significant differences between the last two deglaciations, particularly in Atlantic Meridional Overturning Circulation (AMOC) and Antarctic warming in the deglaciations and the following interglacials. Here, we present transient simulations of deglaciation using a coupled atmosphere–ocean general circulation model for the last two deglaciations focusing on the impact of ice sheet discharge on climate changes associated with the AMOC in the first part, and the sensitivity studies using a Northern Hemisphere ice sheet model in the second part. We show that a set of abrupt climate changes of the last deglaciation, including Bolling–Allerod warming, the Younger Dryas, and onset of the Holocene were simulated with gradual changes of both ice sheet discharge and radiative forcing. On the other hand, penultimate deglaciation, with the abrupt climate change only at the beginning of the last interglacial was simulated when the ice sheet discharge was greater than in the last deglaciation by a factor of 1.5. The results, together with Northern Hemisphere ice sheet model experiments suggest the importance of the transient climate and AMOC responses to the different orbital forcing conditions of the last two deglaciations, through the mechanisms of mass loss of the Northern Hemisphere ice sheet and meltwater influx to the ocean.
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Affiliation(s)
- Takashi Obase
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan.
| | - Ayako Abe-Ouchi
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan.,National Institute of Polar Research, Tachikawa, Japan
| | - Fuyuki Saito
- Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
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13
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Decadal-scale onset and termination of Antarctic ice-mass loss during the last deglaciation. Nat Commun 2021; 12:6683. [PMID: 34795275 PMCID: PMC8602255 DOI: 10.1038/s41467-021-27053-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 11/02/2021] [Indexed: 11/25/2022] Open
Abstract
Emerging ice-sheet modeling suggests once initiated, retreat of the Antarctic Ice Sheet (AIS) can continue for centuries. Unfortunately, the short observational record cannot resolve the tipping points, rate of change, and timescale of responses. Iceberg-rafted debris data from Iceberg Alley identify eight retreat phases after the Last Glacial Maximum that each destabilized the AIS within a decade, contributing to global sea-level rise for centuries to a millennium, which subsequently re-stabilized equally rapidly. This dynamic response of the AIS is supported by (i) a West Antarctic blue ice record of ice-elevation drawdown >600 m during three such retreat events related to globally recognized deglacial meltwater pulses, (ii) step-wise retreat up to 400 km across the Ross Sea shelf, (iii) independent ice sheet modeling, and (iv) tipping point analysis. Our findings are consistent with a growing body of evidence suggesting the recent acceleration of AIS mass loss may mark the beginning of a prolonged period of ice sheet retreat and substantial global sea level rise.
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14
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Deglacial patterns of South Pacific overturning inferred from 231Pa and 230Th. Sci Rep 2021; 11:20473. [PMID: 34650117 PMCID: PMC8517020 DOI: 10.1038/s41598-021-00111-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 10/06/2021] [Indexed: 11/25/2022] Open
Abstract
The millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC) is well documented for the last glacial termination and beyond. Despite its importance for the climate system, the evolution of the South Pacific overturning circulation (SPOC) is by far less well understood. A recently published study highlights the potential applicability of the 231Pa/230Th-proxy in the Pacific. Here, we present five sedimentary down-core profiles of 231Pa/230Th-ratios measured on a depth transect from the Pacific sector of the Southern Ocean to test this hypothesis using downcore records. Our data are consistent with an increase in SPOC as early as 20 ka that peaked during Heinrich Stadial 1. The timing indicates that the SPOC did not simply react to AMOC changes via the bipolar seesaw but were triggered via Southern Hemisphere processes.
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15
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Starr A, Hall IR, Barker S, Rackow T, Zhang X, Hemming SR, van der Lubbe HJL, Knorr G, Berke MA, Bigg GR, Cartagena-Sierra A, Jiménez-Espejo FJ, Gong X, Gruetzner J, Lathika N, LeVay LJ, Robinson RS, Ziegler M. Antarctic icebergs reorganize ocean circulation during Pleistocene glacials. Nature 2021; 589:236-241. [PMID: 33442043 DOI: 10.1038/s41586-020-03094-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 10/20/2020] [Indexed: 01/29/2023]
Abstract
The dominant feature of large-scale mass transfer in the modern ocean is the Atlantic meridional overturning circulation (AMOC). The geometry and vigour of this circulation influences global climate on various timescales. Palaeoceanographic evidence suggests that during glacial periods of the past 1.5 million years the AMOC had markedly different features from today1; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled2. An absence of evidence on the origin of this phenomenon means that the sequence of events leading to global glacial conditions remains unclear. Here we present multi-proxy evidence showing that northward shifts in Antarctic iceberg melt in the Indian-Atlantic Southern Ocean (0-50° E) systematically preceded deep-water mass reorganizations by one to two thousand years during Pleistocene-era glaciations. With the aid of iceberg-trajectory model experiments, we demonstrate that such a shift in iceberg trajectories during glacial periods can result in a considerable redistribution of freshwater in the Southern Ocean. We suggest that this, in concert with increased sea-ice cover, enabled positive buoyancy anomalies to 'escape' into the upper limb of the AMOC, providing a teleconnection between surface Southern Ocean conditions and the formation of NADW. The magnitude and pacing of this mechanism evolved substantially across the mid-Pleistocene transition, and the coeval increase in magnitude of the 'southern escape' and deep circulation perturbations implicate this mechanism as a key feedback in the transition to the '100-kyr world', in which glacial-interglacial cycles occur at roughly 100,000-year periods.
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Affiliation(s)
- Aidan Starr
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK.
| | - Ian R Hall
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK.
| | - Stephen Barker
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK
| | - Thomas Rackow
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Xu Zhang
- Center for Pan Third Pole Environment (Pan-TPE), Key Laboratory of Western China's Environmental Systems, (Ministry of Education), College of Earth and Environmental Science, Lanzhou University, Lanzhou, China.,CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences (CAS), Beijing, China
| | - Sidney R Hemming
- Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA
| | - H J L van der Lubbe
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK.,Faculty of Science, Vrije University, Amsterdam, The Netherlands
| | - Gregor Knorr
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Melissa A Berke
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Grant R Bigg
- Department of Geography, University of Sheffield, Sheffield, UK
| | - Alejandra Cartagena-Sierra
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Francisco J Jiménez-Espejo
- Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Spain.,Research Institute for Marine Resources Utilization (Biogeochemistry Program), JAMSTEC, Yokosuka, Japan
| | - Xun Gong
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.,Hubei Key Laboratory of Marine Geological Resources, China University of Geosciences, Wuhan, China
| | - Jens Gruetzner
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Nambiyathodi Lathika
- National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa, India
| | - Leah J LeVay
- International Ocean Discovery Program, Texas A&M University, College Station, TX, USA
| | - Rebecca S Robinson
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Martin Ziegler
- Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
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16
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Antarctic ice dynamics amplified by Northern Hemisphere sea-level forcing. Nature 2020; 587:600-604. [PMID: 33239798 DOI: 10.1038/s41586-020-2916-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 09/16/2020] [Indexed: 11/09/2022]
Abstract
Sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing is thought to have caused grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS)1-3. Such interhemispheric sea-level forcing may explain the synchronous evolution of global ice sheets over ice-age cycles. Recent studies that indicate that the AIS experienced substantial millennial-scale variability during and after the last deglaciation4-7 (roughly 20,000 to 9,000 years ago) provide further evidence of this sea-level forcing. However, global sea-level change as a result of mass loss from ice sheets is strongly nonuniform, owing to gravitational, deformational and Earth rotational effects8, suggesting that the response of AIS grounding lines to Northern Hemisphere sea-level forcing is more complicated than previously modelled1,2,6. Here, using an ice-sheet model coupled to a global sea-level model, we show that AIS dynamics are amplified by Northern Hemisphere sea-level forcing. As a result of this interhemispheric interaction, a large or rapid Northern Hemisphere sea-level forcing enhances grounding-line advance and associated mass gain of the AIS during glaciation, and grounding-line retreat and mass loss during deglaciation. Relative to models without these interactions, the inclusion of Northern Hemisphere sea-level forcing in our model increases the volume of the AIS during the Last Glacial Maximum (about 26,000 to 20,000 years ago), triggers an earlier retreat of the grounding line and leads to millennial-scale variability throughout the last deglaciation. These findings are consistent with geologic reconstructions of the extent of the AIS during the Last Glacial Maximum and subsequent ice-sheet retreat, and with relative sea-level change in Antarctica3-7,9,10.
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17
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Foraminifer and Ostracod Occurrence in a Cool-Water Carbonate Factory of the Cape Adare (Ross Sea, Antarctica): A Key Lecture for the Climatic and Oceanographic Variations in the Last 30,000 Years. GEOSCIENCES 2020. [DOI: 10.3390/geosciences10100413] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Foraminifers and ostracods were studied in a gravity-core recovered near Cape Adare (Ross Sea, Antarctica) with the aim of identifying the climatic and oceanographic variations during the last 30 ka. The sedimentary sequence represents conditions of a cool-water carbonate factory, which evidences that during the Marine Isotope Stage 2 (MIS2) the area was ice-free and very productive. The overall preservation of delicate skeletal remains such as bryozoans and molluscs indicated moderate bottom currents. This carbonate factory was interrupted by some terrigenous levels, representing conditions of instability/retreat of the ice shelves southward. The younger levels were referred to the meltwater pulse (MWP)-1A and 1B events. The Holocene sequence comprised more terrigenous sediments, reflecting high bottom-currents similar to the present-day conditions. Very abundant and well preserved foraminifers and ostracods, representative of shelf-upper slope paleoenvironments, were recovered. Epistominella exigua, among the foraminifers, suggested the influence of the Circumpolar Deep Water during some periods of the late Quaternary. Heavy-test taxa, such as Cibicides refulgens, indicated strengthening bottom hydrodynamics. As for the ostracods, peaks in the presence of Australicythere devexa, Bairdoppilata simplex and Pseudocythere aff. caudata together with significant values of Polycope spp. allowed us to identify environments rich in nutrients with the influence of cold and deep water upwelling phenomena.
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18
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Oceanic forcing of penultimate deglacial and last interglacial sea-level rise. Nature 2020; 577:660-664. [PMID: 31996820 DOI: 10.1038/s41586-020-1931-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 11/09/2019] [Indexed: 11/08/2022]
Abstract
Sea-level histories during the two most recent deglacial-interglacial intervals show substantial differences1-3 despite both periods undergoing similar changes in global mean temperature4,5 and forcing from greenhouse gases6. Although the last interglaciation (LIG) experienced stronger boreal summer insolation forcing than the present interglaciation7, understanding why LIG global mean sea level may have been six to nine metres higher than today has proven particularly challenging2. Extensive areas of polar ice sheets were grounded below sea level during both glacial and interglacial periods, with grounding lines and fringing ice shelves extending onto continental shelves8. This suggests that oceanic forcing by subsurface warming may also have contributed to ice-sheet loss9-12 analogous to ongoing changes in the Antarctic13,14 and Greenland15 ice sheets. Such forcing would have been especially effective during glacial periods, when the Atlantic Meridional Overturning Circulation (AMOC) experienced large variations on millennial timescales16, with a reduction of the AMOC causing subsurface warming throughout much of the Atlantic basin9,12,17. Here we show that greater subsurface warming induced by the longer period of reduced AMOC during the penultimate deglaciation can explain the more-rapid sea-level rise compared with the last deglaciation. This greater forcing also contributed to excess loss from the Greenland and Antarctic ice sheets during the LIG, causing global mean sea level to rise at least four metres above modern levels. When accounting for the combined influences of penultimate and LIG deglaciation on glacial isostatic adjustment, this excess loss of polar ice during the LIG can explain much of the relative sea level recorded by fossil coral reefs and speleothems at intermediate- and far-field sites.
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19
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Huang H, Gutjahr M, Eisenhauer A, Kuhn G. No detectable Weddell Sea Antarctic Bottom Water export during the Last and Penultimate Glacial Maximum. Nat Commun 2020; 11:424. [PMID: 31969564 PMCID: PMC6976697 DOI: 10.1038/s41467-020-14302-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 12/18/2019] [Indexed: 11/30/2022] Open
Abstract
Weddell Sea-derived Antarctic Bottom Water (AABW) is one of the most important deep water masses in the Southern Hemisphere occupying large portions of the deep Southern Ocean (SO) today. While substantial changes in SO-overturning circulation were previously suggested, the state of Weddell Sea AABW export during glacial climates remains poorly understood. Here we report seawater-derived Nd and Pb isotope records that provide evidence for the absence of Weddell Sea-derived AABW in the Atlantic sector of the SO during the last two glacial maxima. Increasing delivery of Antarctic Pb to regions outside the Weddell Sea traced SO frontal displacements during both glacial terminations. The export of Weddell Sea-derived AABW resumed late during glacial terminations, coinciding with the last major atmospheric CO2 rise in the transition to the Holocene and the Eemian. Our new records lend strong support for a previously inferred AABW overturning stagnation event during the peak Eemian interglacial. The Southern Ocean plays a key role in glacial-interglacial transitions and today, Weddell Sea derived Antarctic Bottom Water is one of the most important deep water masses. New records show that in contrast to today, no Weddell Sea water was exported during the last two glacial maxima, providing new insights towards the condition of Antarctic Bottom Water formation in extreme climate states.
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Affiliation(s)
- Huang Huang
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3, 24148, Kiel, Germany.
| | - Marcus Gutjahr
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3, 24148, Kiel, Germany
| | - Anton Eisenhauer
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3, 24148, Kiel, Germany
| | - Gerhard Kuhn
- Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Alten Hafen 26, 27568, Bremerhaven, Germany
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20
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Abstract
Reductions in the thickness and extent of Antarctic ice shelves are triggering increased discharge of marine-terminating glaciers. While the impacts of recent changes are well documented, their role in modulating past ice-sheet dynamics remains poorly constrained. This reflects two persistent issues; first, the effective discrimination of sediments and landforms solely attributable to sub-ice-shelf deposition, and second, challenges in dating these records. Recent progress in deciphering the geological imprint of Antarctic ice shelves is summarised, including advances in dating methods and proxies to reconstruct drivers of change. Finally, we identify several challenges to overcome to fully exploit the paleo record. The recent collapses of ice shelves in Antarctica due to warming make it essential to understand past ice shelf conditions and mechanisms. Here Smith and colleagues review the latest progress in deciphering the geological imprint of Antarctic ice shelves via sediments, landforms and proxy indicators.
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21
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Jackson MS, Kelly MA, Russell JM, Doughty AM, Howley JA, Chipman JW, Cavagnaro D, Nakileza B, Zimmerman SRH. High-latitude warming initiated the onset of the last deglaciation in the tropics. SCIENCE ADVANCES 2019; 5:eaaw2610. [PMID: 31844659 PMCID: PMC6905867 DOI: 10.1126/sciadv.aaw2610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
Atmospheric greenhouse gas concentrations are thought to have synchronized global temperatures during Pleistocene glacial-interglacial cycles, yet their impact relative to changes in high-latitude insolation and ice-sheet extent remains poorly constrained. Here, we use tropical glacial fluctuations to assess the timing of low-latitude temperature changes relative to global climate forcings. We report 10Be ages of moraines in tropical East Africa and South America and show that glaciers reached their maxima at ~29 to 20 ka, during the global Last Glacial Maximum. Tropical glacial recession was underway by 20 ka, before the rapid CO2 rise at ~18.2 ka. This "early" tropical warming was influenced by rising high-latitude insolation and coincident ice-sheet recession in both polar regions, which lowered the meridional thermal gradient and reduced tropical heat export to the high latitudes.
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Affiliation(s)
| | - Meredith A. Kelly
- Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - James M. Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - Alice M. Doughty
- Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA
- Geology Department, Bates College, Lewiston, ME 04240, USA
| | | | | | - David Cavagnaro
- Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Bob Nakileza
- Mountain Resource Centre, Makerere University, Kampala, Uganda
| | - Susan R. H. Zimmerman
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
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22
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Enhanced glacial discharge from the eastern Antarctic Peninsula since the 1700s associated with a positive Southern Annular Mode. Sci Rep 2019; 9:14606. [PMID: 31649324 PMCID: PMC6813350 DOI: 10.1038/s41598-019-50897-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 09/19/2019] [Indexed: 11/08/2022] Open
Abstract
The Antarctic Peninsula Ice Sheet is currently experiencing sustained and accelerating loss of ice. Determining when these changes were initiated and identifying the main drivers is hampered by the short instrumental record (1992 to present). Here we present a 6,250 year record of glacial discharge based on the oxygen isotope composition of diatoms (δ18Odiatom) from a marine core located at the north-eastern tip of the Antarctic Peninsula. We find that glacial discharge - sourced primarily from ice shelf and iceberg melting along the eastern Antarctic Peninsula - remained largely stable between ~6,250 to 1,620 cal. yr BP, with a slight increase in variability until ~720 cal. yr. BP. An increasing trend in glacial discharge occurs after 550 cal. yr BP (A.D. 1400), reaching levels unprecedented during the past 6,250 years after 244 cal. yr BP (A.D. 1706). A marked acceleration in the rate of glacial discharge is also observed in the early part of twentieth century (after A.D. 1912). Enhanced glacial discharge, particularly after the 1700s is linked to a positive Southern Annular Mode (SAM). We argue that a positive SAM drove stronger westerly winds, atmospheric warming and surface ablation on the eastern Antarctic Peninsula whilst simultaneously entraining more warm water into the Weddell Gyre, potentially increasing melting on the undersides of ice shelves. A possible implication of our data is that ice shelves in this region have been thinning for at least ~300 years, potentially predisposing them to collapse under intensified anthropogenic warming.
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23
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Wadham JL, Hawkings JR, Tarasov L, Gregoire LJ, Spencer RGM, Gutjahr M, Ridgwell A, Kohfeld KE. Ice sheets matter for the global carbon cycle. Nat Commun 2019; 10:3567. [PMID: 31417076 PMCID: PMC6695407 DOI: 10.1038/s41467-019-11394-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 07/09/2019] [Indexed: 11/09/2022] Open
Abstract
The cycling of carbon on Earth exerts a fundamental influence upon the greenhouse gas content of the atmosphere, and hence global climate over millennia. Until recently, ice sheets were viewed as inert components of this cycle and largely disregarded in global models. Research in the past decade has transformed this view, demonstrating the existence of uniquely adapted microbial communities, high rates of biogeochemical/physical weathering in ice sheets and storage and cycling of organic carbon (>104 Pg C) and nutrients. Here we assess the active role of ice sheets in the global carbon cycle and potential ramifications of enhanced melt and ice discharge in a warming world.
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Affiliation(s)
- J L Wadham
- University of Bristol, Bristol, BS8 1TH, UK.
| | - J R Hawkings
- National High Magnetic Field Lab and Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL, 32306, USA
- German Research Centre for Geosciences GFZ, 14473, Potsdam, Germany
| | - L Tarasov
- Memorial University, St. John's, NF, A1B 3X9, Canada
| | | | - R G M Spencer
- National High Magnetic Field Lab and Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL, 32306, USA
| | | | - A Ridgwell
- University of California, Riverside, CA, 94720, USA
| | - K E Kohfeld
- Simon Fraser University, Burnaby, BC, 8888, Canada
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24
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Golledge NR, Keller ED, Gomez N, Naughten KA, Bernales J, Trusel LD, Edwards TL. Global environmental consequences of twenty-first-century ice-sheet melt. Nature 2019; 566:65-72. [PMID: 30728520 DOI: 10.1038/s41586-019-0889-9] [Citation(s) in RCA: 176] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 12/21/2018] [Indexed: 11/09/2022]
Abstract
Government policies currently commit us to surface warming of three to four degrees Celsius above pre-industrial levels by 2100, which will lead to enhanced ice-sheet melt. Ice-sheet discharge was not explicitly included in Coupled Model Intercomparison Project phase 5, so effects on climate from this melt are not currently captured in the simulations most commonly used to inform governmental policy. Here we show, using simulations of the Greenland and Antarctic ice sheets constrained by satellite-based measurements of recent changes in ice mass, that increasing meltwater from Greenland will lead to substantial slowing of the Atlantic overturning circulation, and that meltwater from Antarctica will trap warm water below the sea surface, creating a positive feedback that increases Antarctic ice loss. In our simulations, future ice-sheet melt enhances global temperature variability and contributes up to 25 centimetres to sea level by 2100. However, uncertainties in the way in which future changes in ice dynamics are modelled remain, underlining the need for continued observations and comprehensive multi-model assessments.
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Affiliation(s)
- Nicholas R Golledge
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand. .,GNS Science, Lower Hutt, New Zealand.
| | | | - Natalya Gomez
- Earth and Planetary Sciences, McGill University, Montreal, Quebec, Canada
| | | | - Jorge Bernales
- MARUM Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Luke D Trusel
- Department of Geology, Rowan University, Glassboro, NJ, USA
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25
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Nordic Seas polynyas and their role in preconditioning marine productivity during the Last Glacial Maximum. Nat Commun 2018; 9:3959. [PMID: 30262866 PMCID: PMC6160467 DOI: 10.1038/s41467-018-06252-8] [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: 03/26/2018] [Accepted: 08/28/2018] [Indexed: 11/22/2022] Open
Abstract
Arctic and Antarctic polynyas are crucial sites for deep-water formation, which helps sustain global ocean circulation. During glacial times, the occurrence of polynyas proximal to expansive ice sheets in both hemispheres has been proposed to explain limited ocean ventilation and a habitat requirement for marine and higher-trophic terrestrial fauna. Nonetheless, their existence remains equivocal, not least due to the hitherto paucity of sufficiently characteristic proxy data. Here we demonstrate polynya formation in front of the NW Eurasian ice sheets during the Last Glacial Maximum (LGM), which resulted from katabatic winds blowing seaward of the ice shelves and upwelling of warm, sub-surface Atlantic water. These polynyas sustained ice-sheet build-up, ocean ventilation, and marine productivity in an otherwise glacial Arctic desert. Following the catastrophic meltwater discharge from the collapsing ice sheets at ~17.5 ka BP, polynya formation ceased, marine productivity declined dramatically, and sea ice expanded rapidly to cover the entire Nordic Seas. Polynyas potentially played a role in sustaining marine life during the last glacial, yet their presence and importance remains equivocal. This multi-proxy study reconstructs a corridor of polynyas in the Nordic Seas during the last glacial maximum, and reveals a strong association with biological productivity.
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Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials. Nature 2018; 561:383-386. [PMID: 30232420 DOI: 10.1038/s41586-018-0501-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 07/25/2018] [Indexed: 11/08/2022]
Abstract
Understanding ice sheet behaviour in the geological past is essential for evaluating the role of the cryosphere in the climate system and for projecting rates and magnitudes of sea level rise in future warming scenarios1-4. Although both geological data5-7 and ice sheet models3,8 indicate that marine-based sectors of the East Antarctic Ice Sheet were unstable during Pliocene warm intervals, the ice sheet dynamics during late Pleistocene interglacial intervals are highly uncertain3,9,10. Here we provide evidence from marine sedimentological and geochemical records for ice margin retreat or thinning in the vicinity of the Wilkes Subglacial Basin of East Antarctica during warm late Pleistocene interglacial intervals. The most extreme changes in sediment provenance, recording changes in the locus of glacial erosion, occurred during marine isotope stages 5, 9, and 11, when Antarctic air temperatures11 were at least two degrees Celsius warmer than pre-industrial temperatures for 2,500 years or more. Hence, our study indicates a close link between extended Antarctic warmth and ice loss from the Wilkes Subglacial Basin, providing ice-proximal data to support a contribution to sea level from a reduced East Antarctic Ice Sheet during warm interglacial intervals. While the behaviour of other regions of the East Antarctic Ice Sheet remains to be assessed, it appears that modest future warming may be sufficient to cause ice loss from the Wilkes Subglacial Basin.
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A centuries-long delay between a paleo-ice-shelf collapse and grounding-line retreat in the Whales Deep Basin, eastern Ross Sea, Antarctica. Sci Rep 2018; 8:12392. [PMID: 30120261 PMCID: PMC6098127 DOI: 10.1038/s41598-018-29911-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 07/17/2018] [Indexed: 11/08/2022] Open
Abstract
Recent thinning and loss of Antarctic ice shelves has been followed by near synchronous acceleration of ice flow that may eventually lead to sustained deflation and significant contraction in the extent of grounded and floating ice. Here, we present radiocarbon dates from foraminifera that constrain the time elapsed between a previously described paleo-ice-shelf collapse and the subsequent major grounding-line retreat in the Whales Deep Basin (WDB) of eastern Ross Sea. The dates indicate that West Antarctic Ice Sheet (WAIS) grounding-line retreat from the continental shelf edge was underway prior to 14.7 ± 0.4 cal kyr BP. A paleo-ice-shelf collapse occurred at 12.3 ± 0.2 cal kyr BP. The grounding position was maintained on the outer-continental shelf until at least 11.5 ± 0.3 cal kyr BP before experiencing a 200-km retreat. Given the age uncertainties, the major grounding-line retreat lagged ice-shelf collapse by at least two centuries and by as much as fourteen centuries. In the WDB, the centuries-long delay in the retreat of grounded ice was partly due to rapid aggradational stacking of an unusually large volume of grounding-zone-wedge sediment as ice-stream discharge accelerated following ice-shelf collapse. This new deglacial reconstruction shows that ongoing changes to ice shelves may trigger complex dynamics whose consequences are realized only after a significant lag.
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Maier E, Zhang X, Abelmann A, Gersonde R, Mulitza S, Werner M, Méheust M, Ren J, Chapligin B, Meyer H, Stein R, Tiedemann R, Lohmann G. North Pacific freshwater events linked to changes in glacial ocean circulation. Nature 2018; 559:241-245. [PMID: 29995862 DOI: 10.1038/s41586-018-0276-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 05/14/2018] [Indexed: 11/09/2022]
Abstract
There is compelling evidence that episodic deposition of large volumes of freshwater into the oceans strongly influenced global ocean circulation and climate variability during glacial periods1,2. In the North Atlantic region, episodes of massive freshwater discharge to the North Atlantic Ocean were related to distinct cold periods known as Heinrich Stadials1-3. By contrast, the freshwater history of the North Pacific region remains unclear, giving rise to persistent debates about the existence and possible magnitude of climate links between the North Pacific and North Atlantic oceans during Heinrich Stadials4,5. Here we find that there was a strong connection between changes in North Atlantic circulation during Heinrich Stadials and injections of freshwater from the North American Cordilleran Ice Sheet to the northeastern North Pacific. Our record of diatom δ18O (a measure of the ratio of the stable oxygen isotopes 18O and 16O) over the past 50,000 years shows a decrease in surface seawater δ18O of two to three per thousand, corresponding to a decline in salinity of roughly two to four practical salinity units. This coincided with enhanced deposition of ice-rafted debris and a slight cooling of the sea surface in the northeastern North Pacific during Heinrich Stadials 1 and 4, but not during Heinrich Stadial 3. Furthermore, results from our isotope-enabled model6 suggest that warming of the eastern Equatorial Pacific during Heinrich Stadials was crucial for transmitting the North Atlantic signal to the northeastern North Pacific, where the associated subsurface warming resulted in a discernible freshwater discharge from the Cordilleran Ice Sheet during Heinrich Stadials 1 and 4. However, enhanced background cooling across the northern high latitudes during Heinrich Stadial 3-the coldest period in the past 50,000 years7-prevented subsurface warming of the northeastern North Pacific and thus increased freshwater discharge from the Cordilleran Ice Sheet. In combination, our results show that nonlinear ocean-atmosphere background interactions played a complex role in the dynamics linking the freshwater discharge responses of the North Atlantic and North Pacific during glacial periods.
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Affiliation(s)
- E Maier
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
| | - X Zhang
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
| | - A Abelmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - R Gersonde
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - S Mulitza
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - M Werner
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - M Méheust
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - J Ren
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - B Chapligin
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - H Meyer
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - R Stein
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - R Tiedemann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - G Lohmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
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Montelli A, Dowdeswell J, Ottesen D, Johansen S. 3D seismic evidence of buried iceberg ploughmarks from the mid-Norwegian continental margin reveals largely persistent North Atlantic Current through the Quaternary. MARINE GEOLOGY 2018; 399:66-83. [PMID: 29725141 PMCID: PMC5890382 DOI: 10.1016/j.margeo.2017.11.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 11/13/2017] [Accepted: 11/25/2017] [Indexed: 06/08/2023]
Abstract
Over 7500 buried linear and curvilinear depressions interpreted as iceberg ploughmarks were identified within the Quaternary Naust Formation from an extensive three-dimensional seismic dataset that covers ~ 40,000 km2 of the mid-Norwegian continental margin. The morphology and net orientation of ploughmarks were mapped and analysed. These features are up to 28 km long, 700 m wide and are incised up to 31 m deep. On average, ploughmarks are incised 5 m deep, with median width of 185 m and median lengths ranging from 1.2 to 2.7 km for individual palaeo-surfaces. Width to depth ratio ranges from 8:1 to 400:1 and is on average 36:1. The presence of ploughmarks buried deeply within some palaeo-slope surfaces implies the occasional presence of very large icebergs since the middle Quaternary, suggesting that thick ice-sheet margins with fast-flowing ice streams were present in order to calve icebergs of such dimensions into the Norwegian Sea. The wide geographical distribution of ploughmarks suggests unrestricted iceberg drift and an open Norwegian Sea during the periods of iceberg calving since the early Quaternary. Ploughmark trajectory analysis demonstrates that the ocean current circulation, now dominated by the northeasterly flowing Norwegian Atlantic Current (NwAC), has largely persisted throughout the Quaternary. Despite the overall strikingly consistent pattern of iceberg drift, ploughmark mapping also shows evidence for short-lived NwAC reductions possibly related to major phases of iceberg discharge and/or meltwater pulses from the Fennoscandian Ice Sheet during the middle and late Quaternary.
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Affiliation(s)
- A. Montelli
- Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK
| | - J.A. Dowdeswell
- Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK
| | - D. Ottesen
- Geological Survey of Norway, Trondheim N-7491, Norway
| | - S.E. Johansen
- Department of Petroleum Engineering and Applied Geophysics, Norwegian University of Science and Technology, Trondheim N-7031, Norway
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Silvano A, Rintoul SR, Peña-Molino B, Hobbs WR, van Wijk E, Aoki S, Tamura T, Williams GD. Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water. SCIENCE ADVANCES 2018; 4:eaap9467. [PMID: 29675467 PMCID: PMC5906079 DOI: 10.1126/sciadv.aap9467] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Accepted: 03/06/2018] [Indexed: 05/21/2023]
Abstract
Strong heat loss and brine release during sea ice formation in coastal polynyas act to cool and salinify waters on the Antarctic continental shelf. Polynya activity thus both limits the ocean heat flux to the Antarctic Ice Sheet and promotes formation of Dense Shelf Water (DSW), the precursor to Antarctic Bottom Water. However, despite the presence of strong polynyas, DSW is not formed on the Sabrina Coast in East Antarctica and in the Amundsen Sea in West Antarctica. Using a simple ocean model driven by observed forcing, we show that freshwater input from basal melt of ice shelves partially offsets the salt flux by sea ice formation in polynyas found in both regions, preventing full-depth convection and formation of DSW. In the absence of deep convection, warm water that reaches the continental shelf in the bottom layer does not lose much heat to the atmosphere and is thus available to drive the rapid basal melt observed at the Totten Ice Shelf on the Sabrina Coast and at the Dotson and Getz ice shelves in the Amundsen Sea. Our results suggest that increased glacial meltwater input in a warming climate will both reduce Antarctic Bottom Water formation and trigger increased mass loss from the Antarctic Ice Sheet, with consequences for the global overturning circulation and sea level rise.
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Affiliation(s)
- Alessandro Silvano
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
- Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Hobart, Tasmania, Australia
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
- Corresponding author.
| | - Stephen Rich Rintoul
- Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Hobart, Tasmania, Australia
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
- Centre for Southern Hemisphere Oceans Research, Hobart, Tasmania, Australia
| | - Beatriz Peña-Molino
- Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Hobart, Tasmania, Australia
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
- Centre for Southern Hemisphere Oceans Research, Hobart, Tasmania, Australia
| | - William Richard Hobbs
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
- Australian Research Council Centre of Excellence for Climate System Science, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Esmee van Wijk
- Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Hobart, Tasmania, Australia
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
| | - Shigeru Aoki
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - Takeshi Tamura
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
- National Institute of Polar Research, Tachikawa, Japan
- SOKENDAI, Graduate University for Advanced Studies, Tachikawa, Japan
| | - Guy Darvall Williams
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
- Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
- Australian Research Council Centre of Excellence for Climate System Science, University of New South Wales, Sydney, New South Wales 2052, Australia
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31
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Abstract
Climate models generally fail to produce a warmer (by as much as 0.5 °C) early to mid-Holocene than the pre-industrial in the global annual temperature, which has been termed the Holocene temperature conundrum. Here we use a fully coupled atmosphere-ocean general circulation model to test whether the conundrum can be partially resolved by considering the fact that atmospheric dust loading was much reduced during the early to mid-Holocene. Our experiments show that the global annual mean surface temperature increases by 0.30 °C and 0.23 °C for the mid-Holocene (6 ka) and early Holocene (9 ka), respectively, if the dust is completely removed. The temperature increase scales almost linearly with the fraction of dust being removed, with the 50% dust reduction experiment for the 6 ka being the only one deviating from the linear trend. The indirect effect of dust, which is highly uncertain and is not included in the model, may further enhance the warming. Therefore, the neglect of dust reduction in the Holocene in climate models could contribute significantly to the model-data discrepancy, especially in the Northern Hemisphere.
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32
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Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation. Nat Commun 2017; 8:14798. [PMID: 28303885 PMCID: PMC5357866 DOI: 10.1038/ncomms14798] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 02/01/2017] [Indexed: 01/29/2023] Open
Abstract
The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies. The glaciated history of South Georgia is debated, with many suggesting a coastal limit to the island's ice cap during the last glaciation. Here, the authors show extensive ice-cap cover of the continental block during this time and a readvance of glaciers to fjord mouths during the Antarctic Cold Reversal.
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33
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Fogwill CJ, Turney CSM, Golledge NR, Etheridge DM, Rubino M, Thornton DP, Baker A, Woodward J, Winter K, van Ommen TD, Moy AD, Curran MAJ, Davies SM, Weber ME, Bird MI, Munksgaard NC, Menviel L, Rootes CM, Ellis B, Millman H, Vohra J, Rivera A, Cooper A. Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination. Sci Rep 2017; 7:39979. [PMID: 28054598 PMCID: PMC5215443 DOI: 10.1038/srep39979] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 11/29/2016] [Indexed: 11/17/2022] Open
Abstract
Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.
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Affiliation(s)
- C J Fogwill
- PANGEA Research Centre, University of New South Wales, 2052, Australia.,Climate Change Research Centre, School of Biological Earth and Environmental Sciences, University of New South Wales, 2052, Australia
| | - C S M Turney
- PANGEA Research Centre, University of New South Wales, 2052, Australia.,Climate Change Research Centre, School of Biological Earth and Environmental Sciences, University of New South Wales, 2052, Australia
| | - N R Golledge
- Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand.,GNS Science, Avalon, Lower Hutt, New Zealand
| | - D M Etheridge
- CSIRO Climate Science Centre, Oceans and Atmosphere, Aspendale, Victoria, 3195 Australia
| | - M Rubino
- CSIRO Climate Science Centre, Oceans and Atmosphere, Aspendale, Victoria, 3195 Australia.,Dipartimento di Matematica e Fisica, Università della Campania - Luigi Vanvitelli, viale Lincoln, 5-81100 Caserta, Italy
| | - D P Thornton
- CSIRO Climate Science Centre, Oceans and Atmosphere, Aspendale, Victoria, 3195 Australia
| | - A Baker
- PANGEA Research Centre, University of New South Wales, 2052, Australia
| | - J Woodward
- Department of Geography, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, NE1 8ST, United Kingdom
| | - K Winter
- Department of Geography, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, NE1 8ST, United Kingdom
| | - T D van Ommen
- Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania 7050, Australia.,Antarctic Climate &Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
| | - A D Moy
- Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania 7050, Australia.,Antarctic Climate &Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
| | - M A J Curran
- Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania 7050, Australia.,Antarctic Climate &Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
| | - S M Davies
- Department of Geography, College of Science, Swansea University, Swansea, United Kingdom
| | - M E Weber
- Department of Earth Sciences, University of Cambridge, Drummond Street, Cambridge, United Kingdom.,Steinmann Institute, University of Bonn, Poppelsdorfer Schloss, Bonn, Germany
| | - M I Bird
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Australia
| | - N C Munksgaard
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Australia.,Research Institute for the Environment and Livelihoods, Charles Darwin University, Australia
| | - L Menviel
- PANGEA Research Centre, University of New South Wales, 2052, Australia.,Climate Change Research Centre, School of Biological Earth and Environmental Sciences, University of New South Wales, 2052, Australia
| | - C M Rootes
- Department of Geography, University of Sheffield, United Kingdom
| | - B Ellis
- Research School of Earth Sciences, Australian National University, Canberra, Australia
| | - H Millman
- Climate Change Research Centre, School of Biological Earth and Environmental Sciences, University of New South Wales, 2052, Australia
| | - J Vohra
- PANGEA Research Centre, University of New South Wales, 2052, Australia.,Climate Change Research Centre, School of Biological Earth and Environmental Sciences, University of New South Wales, 2052, Australia
| | - A Rivera
- Glaciology and Climate Change Laboratory, Centro de Estudios Cientficos, Valdivia, Arturo Prat 514, Chile.,Department of Geography, University of Chile, Santiago, Chile
| | - A Cooper
- Australian Centre for Ancient DNA, University of Adelaide, 5005, Australia
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34
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Bakker P, Clark PU, Golledge NR, Schmittner A, Weber ME. Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge. Nature 2016; 541:72-76. [DOI: 10.1038/nature20582] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 10/25/2016] [Indexed: 11/09/2022]
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35
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Gregoire LJ, Otto‐Bliesner B, Valdes PJ, Ivanovic R. Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise. GEOPHYSICAL RESEARCH LETTERS 2016; 43:9130-9137. [PMID: 27773954 PMCID: PMC5053285 DOI: 10.1002/2016gl070356] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/11/2016] [Accepted: 08/19/2016] [Indexed: 06/06/2023]
Abstract
Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions of 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.
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Affiliation(s)
| | | | | | - Ruza Ivanovic
- School of Earth and EnvironmentUniversity of LeedsLeedsUK
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36
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Hein AS, Marrero SM, Woodward J, Dunning SA, Winter K, Westoby MJ, Freeman SPHT, Shanks RP, Sugden DE. Mid-Holocene pulse of thinning in the Weddell Sea sector of the West Antarctic ice sheet. Nat Commun 2016; 7:12511. [PMID: 27545202 PMCID: PMC4996935 DOI: 10.1038/ncomms12511] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 07/09/2016] [Indexed: 11/09/2022] Open
Abstract
Establishing the trajectory of thinning of the West Antarctic ice sheet (WAIS) since the last glacial maximum (LGM) is important for addressing questions concerning ice sheet (in)stability and changes in global sea level. Here we present detailed geomorphological and cosmogenic nuclide data from the southern Ellsworth Mountains in the heart of the Weddell Sea embayment that suggest the ice sheet, nourished by increased snowfall until the early Holocene, was close to its LGM thickness at 10 ka. A pulse of rapid thinning caused the ice elevation to fall ∼400 m to the present level at 6.5-3.5 ka, and could have contributed 1.4-2 m to global sea-level rise. These results imply that the Weddell Sea sector of the WAIS contributed little to late-glacial pulses in sea-level rise but was involved in mid-Holocene rises. The stepped decline is argued to reflect marine downdraw triggered by grounding line retreat into Hercules Inlet.
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Affiliation(s)
- Andrew S Hein
- School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK
| | - Shasta M Marrero
- School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK
| | - John Woodward
- Department of Geography, Northumbria University, Ellison Place, Newcastle upon Tyne NE1 8ST, UK
| | - Stuart A Dunning
- Department of Geography, Northumbria University, Ellison Place, Newcastle upon Tyne NE1 8ST, UK.,School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - Kate Winter
- Department of Geography, Northumbria University, Ellison Place, Newcastle upon Tyne NE1 8ST, UK
| | - Matthew J Westoby
- Department of Geography, Northumbria University, Ellison Place, Newcastle upon Tyne NE1 8ST, UK
| | - Stewart P H T Freeman
- Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride G75 0QF, UK
| | - Richard P Shanks
- Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride G75 0QF, UK
| | - David E Sugden
- School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK
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37
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Marcott SA, Bauska TK, Buizert C, Steig EJ, Rosen JL, Cuffey KM, Fudge TJ, Severinghaus JP, Ahn J, Kalk ML, McConnell JR, Sowers T, Taylor KC, White JWC, Brook EJ. Centennial-scale changes in the global carbon cycle during the last deglaciation. Nature 2014; 514:616-9. [PMID: 25355363 DOI: 10.1038/nature13799] [Citation(s) in RCA: 319] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 08/27/2014] [Indexed: 11/09/2022]
Abstract
Global climate and the concentration of atmospheric carbon dioxide (CO2) are correlated over recent glacial cycles. The combination of processes responsible for a rise in atmospheric CO2 at the last glacial termination (23,000 to 9,000 years ago), however, remains uncertain. Establishing the timing and rate of CO2 changes in the past provides critical insight into the mechanisms that influence the carbon cycle and helps put present and future anthropogenic emissions in context. Here we present CO2 and methane (CH4) records of the last deglaciation from a new high-accumulation West Antarctic ice core with unprecedented temporal resolution and precise chronology. We show that although low-frequency CO2 variations parallel changes in Antarctic temperature, abrupt CO2 changes occur that have a clear relationship with abrupt climate changes in the Northern Hemisphere. A significant proportion of the direct radiative forcing associated with the rise in atmospheric CO2 occurred in three sudden steps, each of 10 to 15 parts per million. Every step took place in less than two centuries and was followed by no notable change in atmospheric CO2 for about 1,000 to 1,500 years. Slow, millennial-scale ventilation of Southern Ocean CO2-rich, deep-ocean water masses is thought to have been fundamental to the rise in atmospheric CO2 associated with the glacial termination, given the strong covariance of CO2 levels and Antarctic temperatures. Our data establish a contribution from an abrupt, centennial-scale mode of CO2 variability that is not directly related to Antarctic temperature. We suggest that processes operating on centennial timescales, probably involving the Atlantic meridional overturning circulation, seem to be influencing global carbon-cycle dynamics and are at present not widely considered in Earth system models.
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Affiliation(s)
- Shaun A Marcott
- 1] College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA [2] Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Thomas K Bauska
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Christo Buizert
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Eric J Steig
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA
| | - Julia L Rosen
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Kurt M Cuffey
- Department of Geography, University of California, Berkeley, California 94720, USA
| | - T J Fudge
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA
| | - Jeffery P Severinghaus
- Scripps Institution of Oceanography, University of California, San Diego, California 92037, USA
| | - Jinho Ahn
- School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742, South Korea
| | - Michael L Kalk
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Joseph R McConnell
- Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512, USA
| | - Todd Sowers
- Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Kendrick C Taylor
- Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512, USA
| | - James W C White
- INSTAAR, University of Colorado, Boulder, Colorado 80309, USA
| | - Edward J Brook
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
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Permafrost thawing as a possible source of abrupt carbon release at the onset of the Bølling/Allerød. Nat Commun 2014; 5:5520. [PMID: 25409739 PMCID: PMC4263146 DOI: 10.1038/ncomms6520] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 10/09/2014] [Indexed: 11/09/2022] Open
Abstract
One of the most abrupt and yet unexplained past rises in atmospheric CO2 (>10 p.p.m.v. in two centuries) occurred in quasi-synchrony with abrupt northern hemispheric warming into the Bølling/Allerød, ~14,600 years ago. Here we use a U/Th-dated record of atmospheric Δ14C from Tahiti corals to provide an independent and precise age control for this CO2 rise. We also use model simulations to show that the release of old (nearly 14C-free) carbon can explain these changes in CO2 and Δ14C. The Δ14C record provides an independent constraint on the amount of carbon released (~125 Pg C). We suggest, in line with observations of atmospheric CH4 and terrigenous biomarkers, that thawing permafrost in high northern latitudes could have been the source of carbon, possibly with contribution from flooding of the Siberian continental shelf during meltwater pulse 1A. Our findings highlight the potential of the permafrost carbon reservoir to modulate abrupt climate changes via greenhouse-gas feedbacks. Ice core records show evidence for an abrupt, and thus far unexplained, increase in atmospheric CO2 levels ~14,600 years ago. Here, the authors combine ice core data, a precisely dated decline in atmospheric 14C and numerical simulations, and propose thawing permafrost as a possible source of this event.
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Golledge NR, Menviel L, Carter L, Fogwill CJ, England MH, Cortese G, Levy RH. Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning. Nat Commun 2014; 5:5107. [DOI: 10.1038/ncomms6107] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 08/29/2014] [Indexed: 11/09/2022] Open
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