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DiNezio PN, Tierney JE, Otto-Bliesner BL, Timmermann A, Bhattacharya T, Rosenbloom N, Brady E. Glacial changes in tropical climate amplified by the Indian Ocean. SCIENCE ADVANCES 2018; 4:eaat9658. [PMID: 30547084 PMCID: PMC6291310 DOI: 10.1126/sciadv.aat9658] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 11/14/2018] [Indexed: 05/26/2023]
Abstract
The mechanisms driving glacial-interglacial changes in the climate of the Indo-Pacific warm pool are poorly understood. Here, we address this question by combining paleoclimate proxies with model simulations of the Last Glacial Maximum climate. We find evidence of two mechanisms explaining key patterns of ocean cooling and rainfall change interpreted from proxy data. Exposure of the Sahul shelf excites a positive ocean-atmosphere feedback involving a stronger surface temperature gradient along the equatorial Indian Ocean and a weaker Walker circulation-a response explaining the drier/wetter dipole across the basin. Northern Hemisphere cooling by ice sheet albedo drives a monsoonal retreat across Africa and the Arabian Peninsula-a response that triggers a weakening of the Indian monsoon via cooling of the Arabian Sea and associated reductions in moisture supply. These results demonstrate the importance of air-sea interactions in the Indian Ocean, amplifying externally forced climate changes over a large part of the tropics.
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Affiliation(s)
- Pedro N. DiNezio
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, J.J. Pickle Research Campus, Building 196 10100 Burnet Road (R2200), Austin, TX 78758, USA
| | - Jessica E. Tierney
- Department of Geosciences, The University of Arizona, 1040 E 4th Street, Tucson, AZ 85721, USA
| | - Bette L. Otto-Bliesner
- National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, 1850 Table Mesa Drive, Boulder, CO 80305, USA
| | - Axel Timmermann
- Center for Climate Physics, Institute for Basic Science, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, South Korea
- Pusan National University, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, South Korea
| | - Tripti Bhattacharya
- Department of Earth Science, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244-1070, USA
| | - Nan Rosenbloom
- National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, 1850 Table Mesa Drive, Boulder, CO 80305, USA
| | - Esther Brady
- National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, 1850 Table Mesa Drive, Boulder, CO 80305, USA
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2
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MacGregor JA, Fahnestock MA, Catania GA, Aschwanden A, Clow GD, Colgan WT, Gogineni SP, Morlighem M, Nowicki SMJ, Paden JD, Price SF, Seroussi H. A synthesis of the basal thermal state of the Greenland Ice Sheet. JOURNAL OF GEOPHYSICAL RESEARCH. EARTH SURFACE 2016; 121:1328-1350. [PMID: 28163988 PMCID: PMC5289704 DOI: 10.1002/2015jf003803] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The basal thermal state of an ice sheet (frozen or thawed) is an important control upon its evolution, dynamics and response to external forcings. However, this state can only be observed directly within sparse boreholes or inferred conclusively from the presence of subglacial lakes. Here we synthesize spatially extensive inferences of the basal thermal state of the Greenland Ice Sheet to better constrain this state. Existing inferences include outputs from the eight thermomechanical ice-flow models included in the SeaRISE effort. New remote-sensing inferences of the basal thermal state are derived from Holocene radiostratigraphy, modern surface velocity and MODIS imagery. Both thermomechanical modeling and remote inferences generally agree that the Northeast Greenland Ice Stream and large portions of the southwestern ice-drainage systems are thawed at the bed, whereas the bed beneath the central ice divides, particularly their west-facing slopes, is frozen. Elsewhere, there is poor agreement regarding the basal thermal state. Both models and remote inferences rarely represent the borehole-observed basal thermal state accurately near NorthGRIP and DYE-3. This synthesis identifies a large portion of the Greenland Ice Sheet (about one third by area) where additional observations would most improve knowledge of its overall basal thermal state.
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Affiliation(s)
- Joseph A. MacGregor
- Institute for Geophysics, The University of Texas at Austin, Austin, Texas, USA
| | - Mark A. Fahnestock
- Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Ginny A. Catania
- Institute for Geophysics, The University of Texas at Austin, Austin, Texas, USA
- Dept. of Geological Sciences, The University of Texas at Austin, Austin, Texas, USA
| | - Andy Aschwanden
- Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Gary D. Clow
- U.S. Geological Survey, Denver, Colorado, USA
- Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, USA
| | - William T. Colgan
- Dept. of Earth and Space Science and Engineering, York University, Toronto, Canada
| | - S. Prasad Gogineni
- Center for Remote Sensing of Ice Sheets, The University of Kansas, Lawrence, Kansas, USA
| | - Mathieu Morlighem
- Dept. of Earth System Science, University of California, Irvine, California, USA
| | - Sophie M. J. Nowicki
- Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - John D. Paden
- Center for Remote Sensing of Ice Sheets, The University of Kansas, Lawrence, Kansas, USA
| | - Stephen F. Price
- Fluid Dynamics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
| | - Hélène Seroussi
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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Dutton A, Carlson AE, Long AJ, Milne GA, Clark PU, DeConto R, Horton BP, Rahmstorf S, Raymo ME. SEA-LEVEL RISE. Sea-level rise due to polar ice-sheet mass loss during past warm periods. Science 2015; 349:aaa4019. [PMID: 26160951 DOI: 10.1126/science.aaa4019] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Interdisciplinary studies of geologic archives have ushered in a new era of deciphering magnitudes, rates, and sources of sea-level rise from polar ice-sheet loss during past warm periods. Accounting for glacial isostatic processes helps to reconcile spatial variability in peak sea level during marine isotope stages 5e and 11, when the global mean reached 6 to 9 meters and 6 to 13 meters higher than present, respectively. Dynamic topography introduces large uncertainties on longer time scales, precluding robust sea-level estimates for intervals such as the Pliocene. Present climate is warming to a level associated with significant polar ice-sheet loss in the past. Here, we outline advances and challenges involved in constraining ice-sheet sensitivity to climate change with use of paleo-sea level records.
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Affiliation(s)
- A Dutton
- Department of Geological Sciences, University of Florida,Gainesville, FL 32611, USA.
| | - A E Carlson
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - A J Long
- Department of Geography, Durham University, Durham, UK
| | - G A Milne
- Department of Earth Sciences, University of Ottawa, Ottawa, Canada
| | - P U Clark
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - R DeConto
- Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA
| | - B P Horton
- Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901, USA. Earth Observatory of Singapore, Nanyang Technological University, Singapore, 639798
| | - S Rahmstorf
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - M E Raymo
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
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MacGregor JA, Fahnestock MA, Catania GA, Paden JD, Prasad Gogineni S, Young SK, Rybarski SC, Mabrey AN, Wagman BM, Morlighem M. Radiostratigraphy and age structure of the Greenland Ice Sheet. JOURNAL OF GEOPHYSICAL RESEARCH. EARTH SURFACE 2015; 120:212-241. [PMID: 26213664 PMCID: PMC4508962 DOI: 10.1002/2014jf003215] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 01/14/2015] [Indexed: 05/25/2023]
Abstract
UNLABELLED Several decades of ice-penetrating radar surveys of the Greenland and Antarctic ice sheets have observed numerous widespread internal reflections. Analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections. Here we present a comprehensive deep radiostratigraphy of the Greenland Ice Sheet from airborne deep ice-penetrating radar data collected over Greenland by The University of Kansas between 1993 and 2013. To map this radiostratigraphy efficiently, we developed new techniques for predicting reflection slope from the phase recorded by coherent radars. When integrated along track, these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing. Core-intersecting reflections were dated using synchronized depth-age relationships for six deep ice cores. Additional reflections were dated by matching reflections between transects and by extending reflection-inferred depth-age relationships using the local effective vertical strain rate. The oldest reflections, dating to the Eemian period, are found mostly in the northern part of the ice sheet. Within the onset regions of several fast-flowing outlet glaciers and ice streams, reflections typically do not conform to the bed topography. Disrupted radiostratigraphy is also observed in a region north of the Northeast Greenland Ice Stream that is not presently flowing rapidly. Dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly. This radiostratigraphy provides a new constraint on the dynamics and history of the Greenland Ice Sheet. KEY POINTS Phase information predicts reflection slope and simplifies reflection tracingReflections can be dated away from ice cores using a simple ice flow modelRadiostratigraphy is often disrupted near the onset of fast ice flow.
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Affiliation(s)
- Joseph A MacGregor
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA
| | - Mark A Fahnestock
- Geophysical Institute, University of Alaska Fairbanks Fairbanks, Alaska, USA
| | - Ginny A Catania
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - John D Paden
- Center for Remote Sensing of Ice Sheets, The University of Kansas Lawrence, Kansas, USA
| | - S Prasad Gogineni
- Center for Remote Sensing of Ice Sheets, The University of Kansas Lawrence, Kansas, USA
| | - S Keith Young
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - Susan C Rybarski
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA ; Now at Division of Hydrologic Sciences, Desert Research Institute Reno, Nevada, USA
| | - Alexandria N Mabrey
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - Benjamin M Wagman
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - Mathieu Morlighem
- Department of Earth System Science, University of California Irvine, California, USA
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South Greenland ice-sheet collapse during Marine Isotope Stage 11. Nature 2014; 510:525-8. [DOI: 10.1038/nature13456] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 05/02/2014] [Indexed: 11/08/2022]
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Abstract
During the last interglacial period, ~125,000 years ago, sea level was at least several meters higher than at present, with substantial variability observed for peak sea level at geographically diverse sites. Speculation that the West Antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice-sheet dynamics during this time interval. We provide an internally consistent database of coral U-Th ages to assess last interglacial sea-level observations in the context of isostatic modeling and stratigraphic evidence. These data indicate that global (eustatic) sea level peaked 5.5 to 9 meters above present sea level, requiring smaller ice sheets in both Greenland and Antarctica relative to today and indicating strong sea-level sensitivity to small changes in radiative forcing.
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Affiliation(s)
- A Dutton
- Research School of Earth Sciences, The Australian National University, 1 Mills Road, Canberra, ACT 0200, Australia.
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Colville EJ, Carlson AE, Beard BL, Hatfield RG, Stoner JS, Reyes AV, Ullman DJ. Sr-Nd-Pb Isotope Evidence for Ice-Sheet Presence on Southern Greenland During the Last Interglacial. Science 2011; 333:620-3. [DOI: 10.1126/science.1204673] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Rogozhina I, Martinec Z, Hagedoorn JM, Thomas M, Fleming K. On the long-term memory of the Greenland Ice Sheet. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jf001787] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- I. Rogozhina
- Helmholtz Centre Potsdam; GFZ German Research Centre for Geosciences, Section 1.3: Earth System Modelling; Potsdam Germany
| | - Z. Martinec
- Dublin Institute for Advanced Studies; Dublin Ireland
- Department of Geophysics, Faculty of Mathematics and Physics; Charles University; Prague Czech Republic
| | - J. M. Hagedoorn
- Helmholtz Centre Potsdam; GFZ German Research Centre for Geosciences, Section 1.3: Earth System Modelling; Potsdam Germany
| | - M. Thomas
- Helmholtz Centre Potsdam; GFZ German Research Centre for Geosciences, Section 1.3: Earth System Modelling; Potsdam Germany
| | - K. Fleming
- Western Australian Centre for Geodesy; Curtin University of Technology; Perth, Western Australia Australia
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The Greenland Ice Sheet During the Past 300,000 Years: A Review. DEVELOPMENTS IN QUATERNARY SCIENCES 2011. [DOI: 10.1016/b978-0-444-53447-7.00050-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Holocene thinning of the Greenland ice sheet. Nature 2009; 461:385-8. [PMID: 19759618 DOI: 10.1038/nature08355] [Citation(s) in RCA: 357] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 07/24/2009] [Indexed: 11/08/2022]
Abstract
On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (delta(18)O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta(18)O from GIS ice cores with delta(18)O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of delta(18)O evidence from ice cores, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our delta(18)O-based results are corroborated by the air content of ice cores, a proxy for surface elevation. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.
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11
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Lemieux JM, Sudicky EA, Peltier WR, Tarasov L. Dynamics of groundwater recharge and seepage over the Canadian landscape during the Wisconsinian glaciation. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jf000838] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Tarasov L, Peltier WR. Coevolution of continental ice cover and permafrost extent over the last glacial-interglacial cycle in North America. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jf000661] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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13
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Overpeck JT, Otto-Bliesner BL, Miller GH, Muhs DR, Alley RB, Kiehl JT. Paleoclimatic Evidence for Future Ice-Sheet Instability and Rapid Sea-Level Rise. Science 2006; 311:1747-50. [PMID: 16556837 DOI: 10.1126/science.1115159] [Citation(s) in RCA: 323] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Sea-level rise from melting of polar ice sheets is one of the largest potential threats of future climate change. Polar warming by the year 2100 may reach levels similar to those of 130,000 to 127,000 years ago that were associated with sea levels several meters above modern levels; both the Greenland Ice Sheet and portions of the Antarctic Ice Sheet may be vulnerable. The record of past ice-sheet melting indicates that the rate of future melting and related sea-level rise could be faster than widely thought.
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Affiliation(s)
- Jonathan T Overpeck
- Institute for the Study of Planet Earth, Department of Geosciences, and Department of Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, USA.
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Tarasov L, Peltier WR. Arctic freshwater forcing of the Younger Dryas cold reversal. Nature 2005; 435:662-5. [PMID: 15931219 DOI: 10.1038/nature03617] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Accepted: 04/01/2005] [Indexed: 11/08/2022]
Abstract
The last deglaciation was abruptly interrupted by a millennial-scale reversal to glacial conditions, the Younger Dryas cold event. This cold interval has been connected to a decrease in the rate of North Atlantic Deep Water formation and to a resulting weakening of the meridional overturning circulation owing to surface water freshening. In contrast, an earlier input of fresh water (meltwater pulse 1a), whose origin is disputed, apparently did not lead to a reduction of the meridional overturning circulation. Here we analyse an ensemble of simulations of the drainage chronology of the North American ice sheet in order to identify the geographical release points of freshwater forcing during deglaciation. According to the simulations with our calibrated glacial systems model, the North American ice sheet contributed about half the fresh water of meltwater pulse 1a. During the onset of the Younger Dryas, we find that the largest combined meltwater/iceberg discharge was directed into the Arctic Ocean. Given that the only drainage outlet from the Arctic Ocean was via the Fram Strait into the Greenland-Iceland-Norwegian seas, where North Atlantic Deep Water is formed today, we hypothesize that it was this Arctic freshwater flux that triggered the Younger Dryas cold reversal.
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Affiliation(s)
- Lev Tarasov
- Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7.
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