1
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Fastovich D, Radeloff VC, Zuckerberg B, Williams JW. Legacies of millennial-scale climate oscillations in contemporary biodiversity in eastern North America. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230012. [PMID: 38583476 PMCID: PMC10999273 DOI: 10.1098/rstb.2023.0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 01/22/2024] [Indexed: 04/09/2024] Open
Abstract
The Atlantic meridional overturning circulation (AMOC) has caused significant climate changes over the past 90 000 years. Prior work has hypothesized that these millennial-scale climate variations effected past and contemporary biodiversity, but the effects are understudied. Moreover, few biogeographic models have accounted for uncertainties in palaeoclimatic simulations of millennial-scale variability. We examine whether refuges from millennial-scale climate oscillations have left detectable legacies in the patterns of contemporary species richness in eastern North America. We analyse 13 palaeoclimate estimates from climate simulations and proxy-based reconstructions as predictors for the contemporary richness of amphibians, passerine birds, mammals, reptiles and trees. Results suggest that past climate changes owing to AMOC variations have left weak but detectable imprints on the contemporary richness of mammals and trees. High temperature stability, precipitation increase, and an apparent climate fulcrum in the southeastern United States across millennial-scale climate oscillations aligns with high biodiversity in the region. These findings support the hypothesis that the southeastern United States may have acted as a biodiversity refuge. However, for some taxa, the strength and direction of palaeoclimate-richness relationships varies among different palaeoclimate estimates, pointing to the importance of palaeoclimatic ensembles and the need for caution when basing biogeographic interpretations on individual palaeoclimate simulations. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.
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Affiliation(s)
- David Fastovich
- Department of Geography, University of Wisconsin–Madison, 550 North Park Street, Madison, WI 53706, USA
- Department of Earth and Environmental Sciences, Syracuse University, 141 Crouse Drive, Syracuse, NY 13210, USA
| | - Volker C. Radeloff
- SILVIS Laboratory, Department of Forest and Wildlife Ecology, University of Wisconsin–Madison, 1630 Linden Drive, Madison, WI 53706, USA
| | - Benjamin Zuckerberg
- Department of Forest and Wildlife Ecology, University of Wisconsin–Madison, 1630 Linden Drive, Madison, WI 53706, USA
| | - John W. Williams
- Department of Geography, University of Wisconsin–Madison, 550 North Park Street, Madison, WI 53706, USA
- Center for Climatic Research, University of Wisconsin–Madison, 550 North Park Street, Madison, WI 53706, USA
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2
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Masoum A, Nerger L, Willeit M, Ganopolski A, Lohmann G. Paleoclimate data assimilation with CLIMBER-X: An ensemble Kalman filter for the last deglaciation. PLoS One 2024; 19:e0300138. [PMID: 38573935 PMCID: PMC10994341 DOI: 10.1371/journal.pone.0300138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 02/21/2024] [Indexed: 04/06/2024] Open
Abstract
Using the climate model CLIMBER-X, we present an efficient method for assimilating the temporal evolution of surface temperatures for the last deglaciation covering the period 22000 to 6500 years before the present. The data assimilation methodology combines the data and the underlying dynamical principles governing the climate system to provide a state estimate of the system, which is better than that which could be obtained using just the data or the model alone. In applying an ensemble Kalman filter approach, we make use of the advances in the parallel data assimilation framework (PDAF), which provides parallel data assimilation functionality with a relatively small increase in computation time. We find that the data assimilation solution depends strongly on the background evolution of the decaying ice sheets rather than the assimilated temperatures. Two different ice sheet reconstructions result in a different deglacial meltwater history, affecting the large-scale ocean circulation and, consequently, the surface temperature. We find that the influence of data assimilation is more pronounced on regional scales than on the global mean. In particular, data assimilation has a stronger effect during millennial warming and cooling phases, such as the Bølling-Allerød and Younger Dryas, especially at high latitudes with heterogeneous temperature patterns. Our approach is a step toward a comprehensive paleo-reanalysis on multi-millennial time scales, including incorporating available paleoclimate data and accounting for their uncertainties in representing regional climates.
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Affiliation(s)
- Ahmadreza Masoum
- Section Paleoclimate Dynamics, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Lars Nerger
- Section Paleoclimate Dynamics, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Matteo Willeit
- Department of Earth System Analysis, Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - Andrey Ganopolski
- Department of Earth System Analysis, Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - Gerrit Lohmann
- Section Paleoclimate Dynamics, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
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3
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Christ AJ, Rittenour TM, Bierman PR, Keisling BA, Knutz PC, Thomsen TB, Keulen N, Fosdick JC, Hemming SR, Tison JL, Blard PH, Steffensen JP, Caffee MW, Corbett LB, Dahl-Jensen D, Dethier DP, Hidy AJ, Perdrial N, Peteet DM, Steig EJ, Thomas EK. Deglaciation of northwestern Greenland during Marine Isotope Stage 11. Science 2023; 381:330-335. [PMID: 37471537 DOI: 10.1126/science.ade4248] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 06/21/2023] [Indexed: 07/22/2023]
Abstract
Past interglacial climates with smaller ice sheets offer analogs for ice sheet response to future warming and contributions to sea level rise; however, well-dated geologic records from formerly ice-free areas are rare. Here we report that subglacial sediment from the Camp Century ice core preserves direct evidence that northwestern Greenland was ice free during the Marine Isotope Stage (MIS) 11 interglacial. Luminescence dating shows that sediment just beneath the ice sheet was deposited by flowing water in an ice-free environment 416 ± 38 thousand years ago. Provenance analyses and cosmogenic nuclide data and calculations suggest the sediment was reworked from local materials and exposed at the surface <16 thousand years before deposition. Ice sheet modeling indicates that ice-free conditions at Camp Century require at least 1.4 meters of sea level equivalent contribution from the Greenland Ice Sheet.
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Affiliation(s)
- Andrew J Christ
- Rubenstein School of the Environment and Natural Resources, University of Vermont, Burlington, VT 05405, USA
- Gund Institute for Environment, University of Vermont, Burlington, VT 05405, USA
| | - Tammy M Rittenour
- Department of Geosciences, Utah State University, Logan, UT 84322, USA
| | - Paul R Bierman
- Rubenstein School of the Environment and Natural Resources, University of Vermont, Burlington, VT 05405, USA
- Gund Institute for Environment, University of Vermont, Burlington, VT 05405, USA
| | - Benjamin A Keisling
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78754, USA
| | - Paul C Knutz
- Geological Survey of Denmark and Greenland, 1350 Copenhagen, Denmark
| | - Tonny B Thomsen
- Geological Survey of Denmark and Greenland, 1350 Copenhagen, Denmark
| | - Nynke Keulen
- Geological Survey of Denmark and Greenland, 1350 Copenhagen, Denmark
| | - Julie C Fosdick
- Department of Earth Sciences, University of Connecticut, Storrs, CT 06269, USA
| | - Sidney R Hemming
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
| | - Jean-Louis Tison
- Laboratoire de Glaciologie, DGES-IGEOS, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Pierre-Henri Blard
- Laboratoire de Glaciologie, DGES-IGEOS, Université Libre de Bruxelles, 1050 Brussels, Belgium
- Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, 54500 Nancy, France
| | - Jørgen P Steffensen
- Centre for Ice and Climate, PICE, Niels Bohr Institute, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Marc W Caffee
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Lee B Corbett
- Gund Institute for Environment, University of Vermont, Burlington, VT 05405, USA
| | - Dorthe Dahl-Jensen
- Centre for Ice and Climate, PICE, Niels Bohr Institute, University of Copenhagen, 2200 Copenhagen, Denmark
- Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - David P Dethier
- Department of Geosciences, Williams College, Williamstown, MA 01267, USA
| | - Alan J Hidy
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Nicolas Perdrial
- Rubenstein School of the Environment and Natural Resources, University of Vermont, Burlington, VT 05405, USA
- Department of Geography and Geosciences, University of Vermont, Burlington, VT 05405, USA
| | - Dorothy M Peteet
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
- NASA Goddard Institute for Space Studies, New York, NY 10025, USA
| | - Eric J Steig
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
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4
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Martin KC, Buizert C, Edwards JS, Kalk ML, Riddell-Young B, Brook EJ, Beaudette R, Severinghaus JP, Sowers TA. Bipolar impact and phasing of Heinrich-type climate variability. Nature 2023; 617:100-104. [PMID: 37095266 DOI: 10.1038/s41586-023-05875-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 02/09/2023] [Indexed: 04/26/2023]
Abstract
During the last ice age, the Laurentide Ice Sheet exhibited extreme iceberg discharge events that are recorded in North Atlantic sediments1. These Heinrich events have far-reaching climate impacts, including widespread disruptions to hydrological and biogeochemical cycles2-4. They occurred during Heinrich stadials-cold periods with strongly weakened Atlantic overturning circulation5-7. Heinrich-type variability is not distinctive in Greenland water isotope ratios, a well-dated site temperature proxy8, complicating efforts to assess their regional climate impact and phasing against Antarctic climate change. Here we show that Heinrich events have no detectable temperature impact on Greenland and cooling occurs at the onset of several Heinrich stadials, and that both types of Heinrich variability have a distinct imprint on Antarctic climate. Antarctic ice cores show accelerated warming that is synchronous with increases in methane during Heinrich events, suggesting an atmospheric teleconnection9, despite the absence of a Greenland climate signal. Greenland ice-core nitrogen stable isotope ratios, a sensitive temperature proxy, indicate an abrupt cooling of about three degrees Celsius at the onset of Heinrich Stadial 1 (17.8 thousand years before present, where present is defined as 1950). Antarctic warming lags this cooling by 133 ± 93 years, consistent with an oceanic teleconnection. Paradoxically, proximal sites are less affected by Heinrich events than remote sites, suggesting spatially complex event dynamics.
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Affiliation(s)
- Kaden C Martin
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA.
| | - Christo Buizert
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Jon S Edwards
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Michael L Kalk
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Ben Riddell-Young
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Edward J Brook
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Ross Beaudette
- Scripps Institution of Oceanography, University of California, San Diego, CA, USA
| | | | - Todd A Sowers
- Department of Geosciences, Pennsylvania State University, State College, PA, USA
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5
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Buizert C, Fudge TJ, Roberts WHG, Steig EJ, Sherriff-Tadano S, Ritz C, Lefebvre E, Edwards J, Kawamura K, Oyabu I, Motoyama H, Kahle EC, Jones TR, Abe-Ouchi A, Obase T, Martin C, Corr H, Severinghaus JP, Beaudette R, Epifanio JA, Brook EJ, Martin K, Chappellaz J, Aoki S, Nakazawa T, Sowers TA, Alley RB, Ahn J, Sigl M, Severi M, Dunbar NW, Svensson A, Fegyveresi JM, He C, Liu Z, Zhu J, Otto-Bliesner BL, Lipenkov VY, Kageyama M, Schwander J. Antarctic surface temperature and elevation during the Last Glacial Maximum. Science 2021; 372:1097-1101. [PMID: 34083489 DOI: 10.1126/science.abd2897] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 04/29/2021] [Indexed: 11/02/2022]
Abstract
Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations.
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Affiliation(s)
- Christo Buizert
- College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.
| | - T J Fudge
- Department of Earth and Space Science, University of Washington, Seattle, WA 98195, USA
| | - William H G Roberts
- Geographical and Environmental Sciences, Northumbria University, Newcastle, UK
| | - Eric J Steig
- Department of Earth and Space Science, University of Washington, Seattle, WA 98195, USA
| | - Sam Sherriff-Tadano
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8568, Japan
| | - Catherine Ritz
- Université Grenoble Alpes, CNRS, IRD, IGE, Grenoble, France
| | - Eric Lefebvre
- Université Grenoble Alpes, CNRS, IRD, IGE, Grenoble, France
| | - Jon Edwards
- College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Kenji Kawamura
- National Institute of Polar Research, Tachikawa, Tokyo, Japan.,Department of Polar Science, The Graduate University of Advanced Studies (SOKENDAI), Tokyo, Japan.,Japan Agency for Marine Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Ikumi Oyabu
- National Institute of Polar Research, Tachikawa, Tokyo, Japan
| | | | - Emma C Kahle
- Department of Earth and Space Science, University of Washington, Seattle, WA 98195, USA
| | - Tyler R Jones
- Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA
| | - Ayako Abe-Ouchi
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8568, Japan
| | - Takashi Obase
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8568, Japan
| | | | - Hugh Corr
- British Antarctic Survey, Cambridge, UK
| | - Jeffrey P Severinghaus
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ross Beaudette
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jenna A Epifanio
- College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Edward J Brook
- College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Kaden Martin
- College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | | | - Shuji Aoki
- Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Takakiyo Nakazawa
- Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Todd A Sowers
- School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, South Korea
| | - Richard B Alley
- The Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA
| | - Jinho Ahn
- School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, South Korea
| | - Michael Sigl
- Climate and Environmental Physics, Physics Institute & Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland
| | - Mirko Severi
- Department of Chemistry "Ugo Schiff," University of Florence, Florence, Italy.,Institute of Polar Sciences, ISP-CNR, Venice-Mestre, Italy
| | - Nelia W Dunbar
- New Mexico Bureau of Geology & Mineral Resources, Earth and Environmental Science Department, New Mexico Tech, Socorro, NM 87801, USA
| | - Anders Svensson
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - John M Fegyveresi
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Chengfei He
- Department of Geography, Ohio State University, Columbus, OH 43210, USA
| | - Zhengyu Liu
- Department of Geography, Ohio State University, Columbus, OH 43210, USA
| | - Jiang Zhu
- National Center for Atmospheric Research, Boulder, CO 80307, USA
| | | | - Vladimir Y Lipenkov
- Climate and Environmental Research Laboratory, Arctic and Antarctic Research Institute, St. Petersburg 199397, Russia
| | - Masa Kageyama
- Laboratoire des Sciences du Climat et de l'Environnement-IPSL, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Jakob Schwander
- Climate and Environmental Physics, Physics Institute & Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland
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6
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He C, Liu Z, Otto-Bliesner BL, Brady EC, Zhu C, Tomas R, Buizert C, Severinghaus JP. Abrupt Heinrich Stadial 1 cooling missing in Greenland oxygen isotopes. SCIENCE ADVANCES 2021; 7:7/25/eabh1007. [PMID: 34134984 PMCID: PMC8208719 DOI: 10.1126/sciadv.abh1007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/29/2021] [Indexed: 05/10/2023]
Abstract
Abrupt climate changes during the last deglaciation have been well preserved in proxy records across the globe. However, one long-standing puzzle is the apparent absence of the onset of the Heinrich Stadial 1 (HS1) cold event around 18 ka in Greenland ice core oxygen isotope δ18 O records, inconsistent with other proxies. Here, combining proxy records with an isotope-enabled transient deglacial simulation, we propose that a substantial HS1 cooling onset did indeed occur over the Arctic in winter. However, this cooling signal in the depleted oxygen isotopic composition is completely compensated by the enrichment because of the loss of winter precipitation in response to sea ice expansion associated with AMOC slowdown during extreme glacial climate. In contrast, the Arctic summer warmed during HS1 and YD because of increased insolation and greenhouse gases, consistent with snowline reconstructions. Our work suggests that Greenland δ18 O may substantially underestimate temperature variability during cold glacial conditions.
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Affiliation(s)
- Chengfei He
- College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, China
- Department of Geography, The Ohio State University, Columbus, OH 43210, USA
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Zhengyu Liu
- Department of Geography, The Ohio State University, Columbus, OH 43210, USA.
- College of Geography Sciences, Nanjing Normal University, Nanjing, China
| | - Bette L Otto-Bliesner
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80305, USA
| | - Esther C Brady
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80305, USA
| | - Chenyu Zhu
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao, China
| | - Robert Tomas
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80305, USA
| | - Christo Buizert
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Jeffrey P Severinghaus
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037, USA
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7
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A 120,000-year long climate record from a NW-Greenland deep ice core at ultra-high resolution. Sci Data 2021; 8:141. [PMID: 34040008 PMCID: PMC8155095 DOI: 10.1038/s41597-021-00916-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/07/2021] [Indexed: 11/12/2022] Open
Abstract
We report high resolution measurements of the stable isotope ratios of ancient ice (δ18O, δD) from the North Greenland Eemian deep ice core (NEEM, 77.45° N, 51.06° E). The record covers the period 8–130 ky b2k (y before 2000) with a temporal resolution of ≈0.5 and 7 y at the top and the bottom of the core respectively and contains important climate events such as the 8.2 ky event, the last glacial termination and a series of glacial stadials and interstadials. At its bottom part the record contains ice from the Eemian interglacial. Isotope ratios are calibrated on the SMOW/SLAP scale and reported on the GICC05 (Greenland Ice Core Chronology 2005) and AICC2012 (Antarctic Ice Core Chronology 2012) time scales interpolated accordingly. We also provide estimates for measurement precision and accuracy for both δ18O and δD. Measurement(s) | isotope analysis • water ice core | Technology Type(s) | cavity ring-down spectroscopy | Factor Type(s) | δ18O • δD | Sample Characteristic - Location | Greenland Ice Sheet |
Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14216441
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8
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Lin Y, Hibbert FD, Whitehouse PL, Woodroffe SA, Purcell A, Shennan I, Bradley SL. A reconciled solution of Meltwater Pulse 1A sources using sea-level fingerprinting. Nat Commun 2021; 12:2015. [PMID: 33795667 PMCID: PMC8016857 DOI: 10.1038/s41467-021-21990-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/17/2021] [Indexed: 02/01/2023] Open
Abstract
The most rapid global sea-level rise event of the last deglaciation, Meltwater Pulse 1A (MWP-1A), occurred ∼14,650 years ago. Considerable uncertainty regarding the sources of meltwater limits understanding of the relationship between MWP-1A and the concurrent fast-changing climate. Here we present a data-driven inversion approach, using a glacio-isostatic adjustment model to invert for the sources of MWP-1A via sea-level constraints from six geographically distributed sites. The results suggest contributions from Antarctica, 1.3 m (0-5.9 m; 95% probability), Scandinavia, 4.6 m (3.2-6.4 m) and North America, 12.0 m (5.6-15.4 m), giving a global mean sea-level rise of 17.9 m (15.7-20.2 m) in 500 years. Only a North American dominant scenario successfully predicts the observed sea-level change across our six sites and an Antarctic dominant scenario is firmly refuted by Scottish isolation basin records. Our sea-level based results therefore reconcile with field-based ice-sheet reconstructions.
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Affiliation(s)
- Yucheng Lin
- Department of Geography, Durham University, Durham, UK.
- Research School of Earth Sciences, Australian National University, ACT, Canberra, Australia.
| | - Fiona D Hibbert
- Research School of Earth Sciences, Australian National University, ACT, Canberra, Australia
- Department of Environment and Geography, University of York, York, UK
| | | | | | - Anthony Purcell
- Research School of Earth Sciences, Australian National University, ACT, Canberra, Australia
| | - Ian Shennan
- Department of Geography, Durham University, Durham, UK
| | - Sarah L Bradley
- Department of Geography, The University of Sheffield, Sheffield, UK
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9
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He C, Liu Z, Otto-Bliesner BL, Brady EC, Zhu C, Tomas R, Clark PU, Zhu J, Jahn A, Gu S, Zhang J, Nusbaumer J, Noone D, Cheng H, Wang Y, Yan M, Bao Y. Hydroclimate footprint of pan-Asian monsoon water isotope during the last deglaciation. SCIENCE ADVANCES 2021; 7:eabe2611. [PMID: 33523950 DOI: 10.1126/sciadv.abe2611] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 12/04/2020] [Indexed: 05/05/2023]
Abstract
Oxygen isotope speleothem records exhibit coherent variability over the pan-Asian summer monsoon (AM) region. The hydroclimatic representation of these oxygen isotope records for the AM, however, has remained poorly understood. Here, combining an isotope-enabled Earth system model in transient experiments with proxy records, we show that the widespread AM δ18Oc signal during the last deglaciation (20 to 11 thousand years ago) is accompanied by a continental-scale, coherent hydroclimate footprint, with spatially opposite signs in rainfall. This footprint is generated as a dynamically coherent response of the AM system primarily to meltwater forcing and secondarily to insolation forcing and is further reinforced by atmospheric teleconnection. Hence, widespread δ18Op depletion in the AM region is accompanied by a northward migration of the westerly jet and enhanced southwesterly monsoon wind, as well as increased rainfall from South Asia (India) to northern China but decreased rainfall in southeast China.
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Affiliation(s)
- C He
- College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, China
- Department of Geography, The Ohio State University, Columbus, OH, USA
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Z Liu
- College of Geography Science, Nanjing Normal University, Nanjing, China.
- Department of Geography, The Ohio State University, Columbus, OH, USA
| | - B L Otto-Bliesner
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - E C Brady
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - C Zhu
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
- Department of Geography, The Ohio State University, Columbus, OH, USA
| | - R Tomas
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - P U Clark
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
- School of Geography and Environmental Sciences, University of Ulster, Coleraine, Northern Ireland BT52 1SA, UK
| | - J Zhu
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - A Jahn
- Department for Atmospheric and Oceanic Sciences and Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
| | - S Gu
- School of Oceanography, Shanghai Jiao Tong University, Shanghai, China
- Department of Geography, The Ohio State University, Columbus, OH, USA
| | - J Zhang
- Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, Seattle, WA, USA
- NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, USA
| | - J Nusbaumer
- College of Geography Science, Nanjing Normal University, Nanjing, China
| | - D Noone
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - H Cheng
- Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an, China
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China
- Department of Earth Sciences, University of Minnesota, Minneapolis, MN, USA
| | - Y Wang
- College of Geography Science, Nanjing Normal University, Nanjing, China
| | - M Yan
- College of Geography Science, Nanjing Normal University, Nanjing, China
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Y Bao
- Department of Geography, The Ohio State University, Columbus, OH, USA
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10
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A unifying framework for studying and managing climate-driven rates of ecological change. Nat Ecol Evol 2020; 5:17-26. [PMID: 33288870 DOI: 10.1038/s41559-020-01344-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 10/12/2020] [Indexed: 01/22/2023]
Abstract
During the Anthropocene and other eras of rapidly changing climates, rates of change of ecological systems can be described as fast, slow or abrupt. Fast ecological responses closely track climate change, slow responses substantively lag climate forcing, causing disequilibria and reduced fitness, and abrupt responses are characterized by nonlinear, threshold-type responses at rates that are large relative to background variability and forcing. All three kinds of climate-driven ecological dynamics are well documented in contemporary studies, palaeoecology and invasion biology. This fast-slow-abrupt conceptual framework helps unify a bifurcated climate-change literature, which tends to separately consider the ecological risks posed by slow or abrupt ecological dynamics. Given the prospect of ongoing climate change for the next several decades to centuries of the Anthropocene and wide variations in ecological rates of change, the theory and practice of managing ecological systems should shift attention from target states to target rates. A rates-focused framework broadens the strategic menu for managers to include options to both slow and accelerate ecological rates of change, seeks to reduce mismatch among climate and ecological rates of change, and provides a unified conceptual framework for tackling the distinct risks associated with fast, slow and abrupt ecological rates of change.
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11
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Li T, Robinson LF, Chen T, Wang XT, Burke A, Rae JWB, Pegrum-Haram A, Knowles TDJ, Li G, Chen J, Ng HC, Prokopenko M, Rowland GH, Samperiz A, Stewart JA, Southon J, Spooner PT. Rapid shifts in circulation and biogeochemistry of the Southern Ocean during deglacial carbon cycle events. SCIENCE ADVANCES 2020; 6:6/42/eabb3807. [PMID: 33067227 PMCID: PMC7567589 DOI: 10.1126/sciadv.abb3807] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 08/25/2020] [Indexed: 06/11/2023]
Abstract
The Southern Ocean plays a crucial role in regulating atmospheric CO2 on centennial to millennial time scales. However, observations of sufficient resolution to explore this have been lacking. Here, we report high-resolution, multiproxy records based on precisely dated deep-sea corals from the Southern Ocean. Paired deep (∆14C and δ11B) and surface (δ15N) proxy data point to enhanced upwelling coupled with reduced efficiency of the biological pump at 14.6 and 11.7 thousand years (ka) ago, which would have facilitated rapid carbon release to the atmosphere. Transient periods of unusually well-ventilated waters in the deep Southern Ocean occurred at 16.3 and 12.8 ka ago. Contemporaneous atmospheric carbon records indicate that these Southern Ocean ventilation events are also important in releasing respired carbon from the deep ocean to the atmosphere. Our results thus highlight two distinct modes of Southern Ocean circulation and biogeochemistry associated with centennial-scale atmospheric CO2 jumps during the last deglaciation.
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Affiliation(s)
- Tao Li
- MOE Key Laboratory of Surficial Geochemistry, Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China.
- School of Earth Sciences, University of Bristol, Bristol, UK
| | | | - Tianyu Chen
- MOE Key Laboratory of Surficial Geochemistry, Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - Xingchen T Wang
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA, USA
| | - Andrea Burke
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - James W B Rae
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Albertine Pegrum-Haram
- School of Earth Sciences, University of Bristol, Bristol, UK
- School of Earth Science and Engineering, Imperial College London, London, UK
| | - Timothy D J Knowles
- Bristol Radiocarbon Accelerator Mass Spectrometry Facility, School of Chemistry and School of Arts, University of Bristol, Bristol, UK
| | - Gaojun Li
- MOE Key Laboratory of Surficial Geochemistry, Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - Jun Chen
- MOE Key Laboratory of Surficial Geochemistry, Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - Hong Chin Ng
- School of Earth Sciences, University of Bristol, Bristol, UK
| | | | | | - Ana Samperiz
- School of Earth Sciences, University of Bristol, Bristol, UK
| | | | - John Southon
- School of Physical Sciences, University of California, Irvine, Irvine, CA, USA
| | - Peter T Spooner
- School of Earth Sciences, University of Bristol, Bristol, UK
- Department of Geography, University College London, London, UK
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12
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Praetorius SK, Condron A, Mix AC, Walczak MH, McKay JL, Du J. The role of Northeast Pacific meltwater events in deglacial climate change. SCIENCE ADVANCES 2020; 6:eaay2915. [PMID: 32133399 PMCID: PMC7043920 DOI: 10.1126/sciadv.aay2915] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 11/22/2019] [Indexed: 06/10/2023]
Abstract
Columbia River megafloods occurred repeatedly during the last deglaciation, but the impacts of this fresh water on Pacific hydrography are largely unknown. To reconstruct changes in ocean circulation during this period, we used a numerical model to simulate the flow trajectory of Columbia River megafloods and compiled records of sea surface temperature, paleo-salinity, and deep-water radiocarbon from marine sediment cores in the Northeast Pacific. The North Pacific sea surface cooled and freshened during the early deglacial (19.0-16.5 ka) and Younger Dryas (12.9-11.7 ka) intervals, coincident with the appearance of subsurface water masses depleted in radiocarbon relative to the sea surface. We infer that Pacific meltwater fluxes contributed to net Northern Hemisphere cooling prior to North Atlantic Heinrich Events, and again during the Younger Dryas stadial. Abrupt warming in the Northeast Pacific similarly contributed to hemispheric warming during the Bølling and Holocene transitions. These findings underscore the importance of changes in North Pacific freshwater fluxes and circulation in deglacial climate events.
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Affiliation(s)
| | - Alan Condron
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Alan C. Mix
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Maureen H. Walczak
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Jennifer L. McKay
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Jianghui Du
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
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13
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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: 19] [Impact Index Per Article: 4.8] [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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14
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Muschitiello F, D'Andrea WJ, Schmittner A, Heaton TJ, Balascio NL, deRoberts N, Caffee MW, Woodruff TE, Welten KC, Skinner LC, Simon MH, Dokken TM. Deep-water circulation changes lead North Atlantic climate during deglaciation. Nat Commun 2019; 10:1272. [PMID: 30894523 PMCID: PMC6426850 DOI: 10.1038/s41467-019-09237-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Accepted: 02/26/2019] [Indexed: 11/21/2022] Open
Abstract
Constraining the response time of the climate system to changes in North Atlantic Deep Water (NADW) formation is fundamental to improving climate and Atlantic Meridional Overturning Circulation predictability. Here we report a new synchronization of terrestrial, marine, and ice-core records, which allows the first quantitative determination of the response time of North Atlantic climate to changes in high-latitude NADW formation rate during the last deglaciation. Using a continuous record of deep water ventilation from the Nordic Seas, we identify a ∼400-year lead of changes in high-latitude NADW formation ahead of abrupt climate changes recorded in Greenland ice cores at the onset and end of the Younger Dryas stadial, which likely occurred in response to gradual changes in temperature- and wind-driven freshwater transport. We suggest that variations in Nordic Seas deep-water circulation are precursors to abrupt climate changes and that future model studies should address this phasing. The response time of North Atlantic climate to changes in high-latitude deep-water formation during the last deglaciation is still unclear. Here the authors show that gradual changes in Nordic Seas deep-water circulation systematically lead ahead of abrupt regional climate shifts by ~400 years.
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Affiliation(s)
- Francesco Muschitiello
- Department of Geography, University of Cambridge, Cambridge, CB2 3EN, UK. .,Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, 10964, USA. .,NORCE Norwegian Research Centre and Bjerknes Centre for Climate Research, 5007, Bergen, Norway.
| | - William J D'Andrea
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, 10964, USA
| | - Andreas Schmittner
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, 97331-5503, USA
| | - Timothy J Heaton
- School of Mathematics and Statistics, University of Sheffield, Sheffield, S3 7RH, UK
| | - Nicholas L Balascio
- Department of Geology, College of William and Mary, Williamsburg, VA, 23187, USA
| | - Nicole deRoberts
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, 10964, USA
| | - Marc W Caffee
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN, 47907, USA.,Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Thomas E Woodruff
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN, 47907, USA
| | - Kees C Welten
- Space Sciences Laboratory, University of California, Berkeley, CA, 94720, USA
| | - Luke C Skinner
- Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Margit H Simon
- NORCE Norwegian Research Centre and Bjerknes Centre for Climate Research, 5007, Bergen, Norway
| | - Trond M Dokken
- NORCE Norwegian Research Centre and Bjerknes Centre for Climate Research, 5007, Bergen, Norway
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15
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Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period. Proc Natl Acad Sci U S A 2019; 116:4099-4104. [PMID: 30760586 PMCID: PMC6410777 DOI: 10.1073/pnas.1807261116] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Dansgaard–Oeschger events contained in Greenland ice cores constitute the archetypal record of abrupt climate change. An accurate understanding of these events hinges on interpretation of Greenland records of oxygen and nitrogen isotopes. We present here the important results from a suite of modeled Dansgaard–Oeschger events. These simulations show that the change in oxygen isotope per degree of warming becomes smaller during larger events. Abrupt reductions in sea ice also emerge as a strong control on ice core oxygen isotopes because of the influence on both the moisture source and the regional temperature increase. This work confirms the significance of sea ice for past abrupt warming events. Greenland ice cores provide excellent evidence of past abrupt climate changes. However, there is no universally accepted theory of how and why these Dansgaard–Oeschger (DO) events occur. Several mechanisms have been proposed to explain DO events, including sea ice, ice shelf buildup, ice sheets, atmospheric circulation, and meltwater changes. DO event temperature reconstructions depend on the stable water isotope (δ18O) and nitrogen isotope measurements from Greenland ice cores: interpretation of these measurements holds the key to understanding the nature of DO events. Here, we demonstrate the primary importance of sea ice as a control on Greenland ice core δ18O: 95% of the variability in δ18O in southern Greenland is explained by DO event sea ice changes. Our suite of DO events, simulated using a general circulation model, accurately captures the amplitude of δ18O enrichment during the abrupt DO event onsets. Simulated geographical variability is broadly consistent with available ice core evidence. We find an hitherto unknown sensitivity of the δ18O paleothermometer to the magnitude of DO event temperature increase: the change in δ18O per Kelvin temperature increase reduces with DO event amplitude. We show that this effect is controlled by precipitation seasonality.
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16
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Reconciling glacial Antarctic water stable isotopes with ice sheet topography and the isotopic paleothermometer. Nat Commun 2018; 9:3537. [PMID: 30166550 PMCID: PMC6117368 DOI: 10.1038/s41467-018-05430-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 06/28/2018] [Indexed: 11/26/2022] Open
Abstract
Stable water isotope records from Antarctica are key for our understanding of Quaternary climate variations. However, the exact quantitative interpretation of these important climate proxy records in terms of surface temperature, ice sheet height and other climatic changes is still a matter of debate. Here we report results obtained with an atmospheric general circulation model equipped with water isotopes, run at a high-spatial horizontal resolution of one-by-one degree. Comparing different glacial maximum ice sheet reconstructions, a best model data match is achieved for the PMIP3 reconstruction. Reduced West Antarctic elevation changes between 400 and 800 m lead to further improved agreement with ice core data. Our modern and glacial climate simulations support the validity of the isotopic paleothermometer approach based on the use of present-day observations and reveal that a glacial ocean state as displayed in the GLAMAP reconstruction is suitable for capturing the observed glacial isotope changes in Antarctic ice cores. Despite their importance, the accuracy of the quantitative interpretation of Antarctic ice core stable water isotope records remains a matter of debate. Here, the authors use an isotope-enabled atmospheric general circulation model to test and validate the isotopic paleothermometer approach.
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17
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Cole-Dai J, Peterson KM, Kennedy JA, Cox TS, Ferris DG. Evidence of Influence of Human Activities and Volcanic Eruptions on Environmental Perchlorate from a 300-Year Greenland Ice Core Record. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:8373-8380. [PMID: 29943569 DOI: 10.1021/acs.est.8b01890] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A 300-year (1700-2007) chronological record of environmental perchlorate, reconstructed from high-resolution analysis of a central Greenland ice core, shows that perchlorate levels in the post-1980 atm were two-to-three times those of the pre-1980 environment. While this confirms recent reports of increased perchlorate in Arctic snow since 1980 compared with the levels for the prior decades (1930-1980), the longer Greenland record demonstrates that the Industrial Revolution and other human activities, which emitted large quantities of pollutants and contaminants, did not significantly impact environmental perchlorate, as perchlorate levels remained stable throughout the 18th, 19th, and much of the 20th centuries. The increased levels since 1980 likely result from enhanced atmospheric perchlorate production, rather than from direct release from perchlorate manufacturing and applications. The enhancement is probably influenced by the emission of organic chlorine compounds in the last several decades. Prior to 1980, no significant long-term temporal trends in perchlorate concentration are observed. Brief (a few years) high-concentration episodes appear frequently over an apparently stable and low background (∼1 ng kg-1). Several such episodes coincide in time with large explosive volcanic eruptions including the 1912 Novarupta/Katmai eruption in Alaska. It appears that atmospheric perchlorate production is impacted by large eruptions in both high- and low-latitudes, but not by small eruptions and nonexplosive degassing.
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Affiliation(s)
- Jihong Cole-Dai
- Department of Chemistry and Biochemistry , South Dakota State University , Avera Health and Science Center , Box 2202, Brookings , South Dakota 57007 , United States
| | - Kari M Peterson
- Department of Chemistry and Biochemistry , South Dakota State University , Avera Health and Science Center , Box 2202, Brookings , South Dakota 57007 , United States
| | - Joshua A Kennedy
- Department of Chemistry and Biochemistry , South Dakota State University , Avera Health and Science Center , Box 2202, Brookings , South Dakota 57007 , United States
| | - Thomas S Cox
- Department of Physical Sciences , Butte College , Oroville , California 95965 , United States
| | - David G Ferris
- Department of Earth Sciences , Dartmouth College , Hanover , New Hampshire 03755 , United States
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18
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Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux. Nat Commun 2018; 9:3124. [PMID: 30087327 PMCID: PMC6081422 DOI: 10.1038/s41467-018-05337-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 06/27/2018] [Indexed: 12/22/2022] Open
Abstract
Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North Pacific and North Atlantic in a climate model to determine the sensitivity of Arctic temperatures to zonal heterogeneities in northern hemisphere SST patterns. Both positive and negative ocean heat flux perturbations from the North Pacific result in greater global and Arctic surface air temperature anomalies than equivalent magnitude perturbations from the North Atlantic; a response we primarily attribute to greater moisture flux from the subpolar extratropics to Arctic. Enhanced poleward latent heat and moisture transport drive sea-ice retreat and low-cloud formation in the Arctic, amplifying Arctic surface warming through the ice-albedo feedback and infrared warming effect of low clouds. Our results imply that global climate sensitivity may be dependent on patterns of ocean heat flux in the northern hemisphere.
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19
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Menviel L, Spence P, Yu J, Chamberlain MA, Matear RJ, Meissner KJ, England MH. Southern Hemisphere westerlies as a driver of the early deglacial atmospheric CO 2 rise. Nat Commun 2018; 9:2503. [PMID: 29950652 PMCID: PMC6021399 DOI: 10.1038/s41467-018-04876-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Accepted: 05/25/2018] [Indexed: 11/13/2022] Open
Abstract
The early part of the last deglaciation is characterised by a ~40 ppm atmospheric CO2 rise occurring in two abrupt phases. The underlying mechanisms driving these increases remain a subject of intense debate. Here, we successfully reproduce changes in CO2, δ13C and Δ14C as recorded by paleo-records during Heinrich stadial 1 (HS1). We show that HS1 CO2 increase can be explained by enhanced Southern Ocean upwelling of carbon-rich Pacific deep and intermediate waters, resulting from intensified Southern Ocean convection and Southern Hemisphere (SH) westerlies. While enhanced Antarctic Bottom Water formation leads to a millennial CO2 outgassing, intensified SH westerlies induce a multi-decadal atmospheric CO2 rise. A strengthening of SH westerlies in a global eddy-permitting ocean model further supports a multi-decadal CO2 outgassing from the Southern Ocean. Our results highlight the crucial role of SH westerlies in the global climate and carbon cycle system with important implications for future climate projections. Despite decades of research, the sequence of events leading to the deglacial atmospheric CO2 rise remains unclear. Menviel et al. show that Southern Ocean convection driven by intensified Southern Hemisphere westerlies during Heinrich stadial 1 can explain the abrupt pCO2 rise and changes in atmosphere and ocean carbon isotopes.
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Affiliation(s)
- L Menviel
- Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, University of New South Wales, NSW 2052, Sydney, Australia. .,Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Sydney, Australia.
| | - P Spence
- Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, University of New South Wales, NSW 2052, Sydney, Australia
| | - J Yu
- Research School of Earth Sciences, The Australian National University, ACT 0200, Canberra, Australia
| | | | - R J Matear
- CSIRO Oceans and Atmosphere, ATAS 7004, Hobart, Australia
| | - K J Meissner
- Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, University of New South Wales, NSW 2052, Sydney, Australia
| | - M H England
- Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, University of New South Wales, NSW 2052, Sydney, Australia
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20
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Instability of the Northeast Greenland Ice Stream over the last 45,000 years. Nat Commun 2018; 9:1872. [PMID: 29760384 PMCID: PMC5951810 DOI: 10.1038/s41467-018-04312-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 04/20/2018] [Indexed: 11/16/2022] Open
Abstract
The sensitivity of the Northeast Greenland Ice Stream (NEGIS) to prolonged warm periods is largely unknown and geological records documenting such long-term changes are needed to place current observations in perspective. Here we use cosmogenic surface exposure and radiocarbon ages to determine the magnitude of NEGIS margin fluctuations over the last 45 kyr (thousand years). We find that the NEGIS experienced slow early Holocene ice-margin retreat of 30–40 m a−1, likely as a result of the buttressing effect of sea-ice or shelf-ice. The NEGIS was ~20–70 km behind its present ice-extent ~41–26 ka and ~7.8–1.2 ka; both periods of high orbital precession index and/or summer temperatures within the projected warming for the end of this century. We show that the NEGIS was smaller than present for approximately half of the last ~45 kyr and is susceptible to subtle changes in climate, which has implications for future stability of this ice stream. The outlet glaciers that comprise the Northeast Greenland Ice Stream (NEGIS) have experienced accelerated retreat in recent years, yet their longterm stability remains unclear. Here, via cosmogenic surface exposure and radiocarbon ages, the authors investigate the stability of the NEGIS for the past 45 kyr.
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21
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Schenk F, Väliranta M, Muschitiello F, Tarasov L, Heikkilä M, Björck S, Brandefelt J, Johansson AV, Näslund JO, Wohlfarth B. Warm summers during the Younger Dryas cold reversal. Nat Commun 2018; 9:1634. [PMID: 29691388 PMCID: PMC5915408 DOI: 10.1038/s41467-018-04071-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 03/29/2018] [Indexed: 11/26/2022] Open
Abstract
The Younger Dryas (YD) cold reversal interrupts the warming climate of the deglaciation with global climatic impacts. The sudden cooling is typically linked to an abrupt slowdown of the Atlantic Meridional Overturning Circulation (AMOC) in response to meltwater discharges from ice sheets. However, inconsistencies regarding the YD-response of European summer temperatures have cast doubt whether the concept provides a sufficient explanation. Here we present results from a high-resolution global climate simulation together with a new July temperature compilation based on plant indicator species and show that European summers remain warm during the YD. Our climate simulation provides robust physical evidence that atmospheric blocking of cold westerly winds over Fennoscandia is a key mechanism counteracting the cooling impact of an AMOC-slowdown during summer. Despite the persistence of short warm summers, the YD is dominated by a shift to a continental climate with extreme winter to spring cooling and short growing seasons. Mechanisms causing the Younger Dryas cold reversal have been questioned by inconsistencies between proxy and modelling results. Here, the authors show that the concept of a strong North Atlantic Ocean cooling event as major driver is consistent with warm European summers caused by intensified atmospheric blocking.
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Affiliation(s)
- Frederik Schenk
- Bolin Centre for Climate Research and Department of Geological Sciences, Stockholm University, Svante Arrhenius väg 8, SE106-91, Stockholm, Sweden. .,Department of Mechanics, Linné FLOW Centre, KTH Royal Institute of Technology, Osquars backe 18, SE100-44, Stockholm, Sweden.
| | - Minna Väliranta
- Environmental Change Research Unit (ECRU), Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences and Helsinki Institute of Sustainability Science (HELSUS), University of Helsinki, P.O. Box 65, 00014, Helsinki, Finland
| | - Francesco Muschitiello
- Bolin Centre for Climate Research and Department of Geological Sciences, Stockholm University, Svante Arrhenius väg 8, SE106-91, Stockholm, Sweden.,Department of Geography, University of Cambridge, Cambridge, CB2 3EN, UK.,Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9 W, Palisades, New York, NY, 10964-8000, USA
| | - Lev Tarasov
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, NL, A1B 3X7, Canada
| | - Maija Heikkilä
- Environmental Change Research Unit (ECRU), Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences and Helsinki Institute of Sustainability Science (HELSUS), University of Helsinki, P.O. Box 65, 00014, Helsinki, Finland
| | - Svante Björck
- Bolin Centre for Climate Research and Department of Geological Sciences, Stockholm University, Svante Arrhenius väg 8, SE106-91, Stockholm, Sweden.,Department of Geology, Quaternary Sciences, Lund University, Box 117, SE221-00, Lund, Sweden
| | - Jenny Brandefelt
- Swedish Nuclear Fuel and Waste Management Company (SKB), Box 250, SE101-24, Stockholm, Sweden
| | - Arne V Johansson
- Department of Mechanics, Linné FLOW Centre, KTH Royal Institute of Technology, Osquars backe 18, SE100-44, Stockholm, Sweden
| | - Jens-Ove Näslund
- Swedish Nuclear Fuel and Waste Management Company (SKB), Box 250, SE101-24, Stockholm, Sweden.,Department of Physical Geography and Quaternary Geology, Stockholm University, Svante Arrhenius väg 8, SE106-91, Stockholm, Sweden
| | - Barbara Wohlfarth
- Bolin Centre for Climate Research and Department of Geological Sciences, Stockholm University, Svante Arrhenius väg 8, SE106-91, Stockholm, Sweden
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22
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Cook E, Davies SM, Guðmundsdóttir ER, Abbott PM, Pearce NJG. First identification and characterization of Borrobol-type tephra in the Greenland ice cores: new deposits and improved age estimates. JOURNAL OF QUATERNARY SCIENCE 2018; 33:212-224. [PMID: 29576671 PMCID: PMC5856069 DOI: 10.1002/jqs.3016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 12/02/2017] [Accepted: 12/18/2017] [Indexed: 06/08/2023]
Abstract
Contiguous sampling of ice spanning key intervals of the deglaciation from the Greenland ice cores of NGRIP, GRIP and NEEM has revealed three new silicic cryptotephra deposits that are geochemically similar to the well-known Borrobol Tephra (BT). The BT is complex and confounded by the younger closely timed and compositionally similar Penifiler Tephra (PT). Two of the deposits found in the ice are in Greenland Interstadial 1e (GI-1e) and an older deposit is found in Greenland Stadial 2.1 (GS-2.1). Until now, the BT was confined to GI-1-equivalent lacustrine sequences in the British Isles, Sweden and Germany, and our discovery in Greenland ice extends its distribution and geochemical composition. However, the two cryptotephras that fall within GI-1e ice cannot be separated on the basis of geochemistry and are dated to 14358 ± 177 a b2k and 14252 ± 173 a b2k, just 106 ± 3 years apart. The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI-1e events identified in the ice-cores or that it relates to just one of the ice-core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice-cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine sediment cores from the North Iceland Shelf (ca. 17179-16754 cal a BP). Despite showing similarities to the BT, this deposit can be distinguished on the basis of lower CaO and TiO2 and is a valuable new tie-point that could eventually be used in high-resolution marine records to compare the climate signals from the ocean and atmosphere.
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Affiliation(s)
- Eliza Cook
- Department of GeographySwansea UniversitySwanseaUK
- Centre for Ice and ClimateNiels Bohr InstituteUniversity of CopenhagenDenmark
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23
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Asynchronous warming and δ 18O evolution of deep Atlantic water masses during the last deglaciation. Proc Natl Acad Sci U S A 2017; 114:11075-11080. [PMID: 28973944 DOI: 10.1073/pnas.1704512114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ18O of benthic foraminiferal calcite (δ18Oc). Here, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ18O evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep δ18Oc likely reflects early warming of the deep northern North Atlantic by ∼1.4 °C, while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong middepth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way that ocean circulation affects heat, a dynamic tracer, is considerably different from how it affects passive tracers, like δ18O, and call for caution when inferring water mass changes from δ18Oc records while assuming uniform changes in deep temperatures.
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24
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Nowak RS, Nowak CL, Tausch RJ. Vegetation dynamics during last 35,000 years at a cold desert locale: preferential loss of forbs with increased aridity. Ecosphere 2017. [DOI: 10.1002/ecs2.1873] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Robert S. Nowak
- Department of Natural Resources & Environmental Sciences University of Nevada Reno MS 186, 1664 North Virginia Street Reno Nevada 89557 USA
| | - Cheryl L. Nowak
- U.S. Forest Service Great Basin Research Laboratory 920 Valley Road Reno Nevada 89521 USA
| | - Robin J. Tausch
- U.S. Forest Service Great Basin Research Laboratory 920 Valley Road Reno Nevada 89521 USA
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25
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Kobashi T, Menviel L, Jeltsch-Thömmes A, Vinther BM, Box JE, Muscheler R, Nakaegawa T, Pfister PL, Döring M, Leuenberger M, Wanner H, Ohmura A. Volcanic influence on centennial to millennial Holocene Greenland temperature change. Sci Rep 2017; 7:1441. [PMID: 28469185 PMCID: PMC5431187 DOI: 10.1038/s41598-017-01451-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 03/30/2017] [Indexed: 11/23/2022] Open
Abstract
Solar variability has been hypothesized to be a major driver of North Atlantic millennial-scale climate variations through the Holocene along with orbitally induced insolation change. However, another important climate driver, volcanic forcing has generally been underestimated prior to the past 2,500 years partly owing to the lack of proper proxy temperature records. Here, we reconstruct seasonally unbiased and physically constrained Greenland Summit temperatures over the Holocene using argon and nitrogen isotopes within trapped air in a Greenland ice core (GISP2). We show that a series of volcanic eruptions through the Holocene played an important role in driving centennial to millennial-scale temperature changes in Greenland. The reconstructed Greenland temperature exhibits significant millennial correlations with K+ and Na+ ions in the GISP2 ice core (proxies for atmospheric circulation patterns), and δ18O of Oman and Chinese Dongge cave stalagmites (proxies for monsoon activity), indicating that the reconstructed temperature contains hemispheric signals. Climate model simulations forced with the volcanic forcing further suggest that a series of large volcanic eruptions induced hemispheric-wide centennial to millennial-scale variability through ocean/sea-ice feedbacks. Therefore, we conclude that volcanic activity played a critical role in driving centennial to millennial-scale Holocene temperature variability in Greenland and likely beyond.
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Affiliation(s)
- Takuro Kobashi
- Climate and Environmental Physics, University of Bern, 3012, Bern, Switzerland. .,Oeschger Centre for Climate Change Research, University of Bern, 3012, Bern, Switzerland. .,Renewable Energy Institute, Minato-ku, 105-0003, Tokyo, Japan.
| | - Laurie Menviel
- Climate Change Research Centre and PANGEA Research Centre, University of New South Wales, New South Wales, 2052, Australia.,ARC Centre of Excellence for Climate System Science, New South Wales, Sydney, Australia
| | - Aurich Jeltsch-Thömmes
- Climate and Environmental Physics, University of Bern, 3012, Bern, Switzerland.,Oeschger Centre for Climate Change Research, University of Bern, 3012, Bern, Switzerland
| | - Bo M Vinther
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Jason E Box
- Geological Survey of Greenland and Denmark, 1350, Copenhagen, Denmark
| | - Raimund Muscheler
- Department of Geology, Quaternary Sciences, Lund University, 22362, Lund, Sweden
| | | | - Patrik L Pfister
- Climate and Environmental Physics, University of Bern, 3012, Bern, Switzerland.,Oeschger Centre for Climate Change Research, University of Bern, 3012, Bern, Switzerland
| | - Michael Döring
- Climate and Environmental Physics, University of Bern, 3012, Bern, Switzerland.,Oeschger Centre for Climate Change Research, University of Bern, 3012, Bern, Switzerland
| | - Markus Leuenberger
- Climate and Environmental Physics, University of Bern, 3012, Bern, Switzerland.,Oeschger Centre for Climate Change Research, University of Bern, 3012, Bern, Switzerland
| | - Heinz Wanner
- Oeschger Centre for Climate Change Research, University of Bern, 3012, Bern, Switzerland
| | - Atsumu Ohmura
- Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology ETH Zurich, 8092, Zurich, Switzerland
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26
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Putnam AE, Broecker WS. Human-induced changes in the distribution of rainfall. SCIENCE ADVANCES 2017; 3:e1600871. [PMID: 28580418 PMCID: PMC5451196 DOI: 10.1126/sciadv.1600871] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 04/13/2017] [Indexed: 05/24/2023]
Abstract
A likely consequence of global warming will be the redistribution of Earth's rain belts, affecting water availability for many of Earth's inhabitants. We consider three ways in which planetary warming might influence the global distribution of precipitation. The first possibility is that rainfall in the tropics will increase and that the subtropics and mid-latitudes will become more arid. A second possibility is that Earth's thermal equator, around which the planet's rain belts and dry zones are organized, will migrate northward. This northward shift will be a consequence of the Northern Hemisphere, with its large continental area, warming faster than the Southern Hemisphere, with its large oceanic area. A third possibility is that both of these scenarios will play out simultaneously. We review paleoclimate evidence suggesting that (i) the middle latitudes were wetter during the last glacial maximum, (ii) a northward shift of the thermal equator attended the abrupt Bølling-Allerød climatic transition ~14.6 thousand years ago, and (iii) a southward shift occurred during the more recent Little Ice Age. We also inspect trends in seasonal surface heating between the hemispheres over the past several decades. From these clues, we predict that there will be a seasonally dependent response in rainfall patterns to global warming. During boreal summer, in which the rate of recent warming has been relatively uniform between the hemispheres, wet areas will get wetter and dry regions will become drier. During boreal winter, rain belts and drylands will expand northward in response to differential heating between the hemispheres.
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Affiliation(s)
- Aaron E. Putnam
- School of Earth and Climate Sciences and Climate Change Institute, 224 Bryand Global Sciences Center, University of Maine, Orono, ME 04469, USA
- Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/PO Box 1000, Palisades, NY 10964, USA
| | - Wallace S. Broecker
- Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/PO Box 1000, Palisades, NY 10964, USA
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27
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Abstract
The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth's climate responds to various forcings, including a rise in atmospheric CO2 This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes' sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was [Formula: see text]C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted.
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28
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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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29
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Chen T, Robinson LF, Burke A, Southon J, Spooner P, Morris PJ, Ng HC. Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation. Science 2015; 349:1537-41. [PMID: 26404835 DOI: 10.1126/science.aac6159] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Antarctic ice-core data reveal that the atmosphere experienced abrupt centennial increases in CO2 concentration during the last deglaciation (~18 thousand to 11 thousand years ago). Establishing the role of ocean circulation in these changes requires high-resolution, accurately dated marine records. Here, we report radiocarbon data from uranium-thorium-dated deep-sea corals in the Equatorial Atlantic and Drake Passage over the past 25,000 years. Two major deglacial radiocarbon shifts occurred in phase with centennial atmospheric CO2 rises at 14.8 thousand and 11.7 thousand years ago. We interpret these radiocarbon-enriched signals to represent two short-lived (less than 500 years) "overshoot" events, with Atlantic meridional overturning stronger than that of the modern era. These results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation.
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Affiliation(s)
- Tianyu Chen
- Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK.
| | - Laura F Robinson
- Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK
| | - Andrea Burke
- Department of Earth and Environmental Sciences, University of St Andrews, St. Andrews, UK
| | - John Southon
- School of Physical Sciences, University of California, Irvine, Irvine, CA, USA
| | - Peter Spooner
- Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK
| | - Paul J Morris
- Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK
| | - Hong Chin Ng
- Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK
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30
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Peterson K, Cole-Dai J, Brandis D, Cox T, Splett S. Rapid measurement of perchlorate in polar ice cores down to sub-ng L−1 levels without pre-concentration. Anal Bioanal Chem 2015; 407:7965-72. [DOI: 10.1007/s00216-015-8965-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/17/2015] [Accepted: 08/05/2015] [Indexed: 11/25/2022]
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31
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Precise interpolar phasing of abrupt climate change during the last ice age. Nature 2015; 520:661-5. [PMID: 25925479 DOI: 10.1038/nature14401] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 03/03/2015] [Indexed: 11/09/2022]
Abstract
The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.
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32
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Sime LC. Climate. Greenland deglaciation puzzles. Science 2014; 345:1116-7. [PMID: 25190777 DOI: 10.1126/science.1257842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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