1
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Jansen D, Franke S, Bauer CC, Binder T, Dahl-Jensen D, Eichler J, Eisen O, Hu Y, Kerch J, Llorens MG, Miller H, Neckel N, Paden J, de Riese T, Sachau T, Stoll N, Weikusat I, Wilhelms F, Zhang Y, Bons PD. Shear margins in upper half of Northeast Greenland Ice Stream were established two millennia ago. Nat Commun 2024; 15:1193. [PMID: 38331888 PMCID: PMC10853536 DOI: 10.1038/s41467-024-45021-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 01/09/2024] [Indexed: 02/10/2024] Open
Abstract
Only a few localised ice streams drain most of the ice from the Greenland Ice Sheet. Thus, understanding ice stream behaviour and its temporal variability is crucially important to predict future sea-level change. The interior trunk of the 700 km-long North-East Greenland Ice Stream (NEGIS) is remarkable due to the lack of any clear bedrock channel to explain its presence. Here, we present a 3-dimensional analysis of the folding and advection of its stratigraphic horizons, which shows that the localised flow and shear margins in the upper NEGIS were fully developed only ca 2000 years ago. Our results contradict the assumption that the ice stream has been stable throughout the Holocene in its current form and show that upper NEGIS-type development of ice streaming, with distinct shear margins and no bed topography relationship, can be established on time scales of hundreds of years, which is a major challenge for realistic mass-balance and sea-level rise projections.
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Affiliation(s)
- Daniela Jansen
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
| | - Steven Franke
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | | | - Tobias Binder
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Now at ATLAS ELEKTRONIK GmbH, Bremen, Germany
| | - Dorthe Dahl-Jensen
- Niels Bohr Institute, Physics of Ice, Climate and Earth, University of Copenhagen, Copenhagen, Denmark
- Center for Earth Observation Sciences, University of Manitoba, Winnipeg, Canada
| | - Jan Eichler
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Now at Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (LGL-TPE), ENS Lyon, Université Claude Bernard Lyon 1, CNRS, Villeurbanne, France
| | - Olaf Eisen
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- University of Bremen, Bremen, Germany
| | - Yuanbang Hu
- Department of Geosciences, Tübingen University, Tübingen, Germany
- College of Earth Science, Chengdu University of Technology, Chengdu, China
| | - Johanna Kerch
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Geoscience Centre, University of Göttingen, Göttingen, Germany
| | | | - Heinrich Miller
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Niklas Neckel
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - John Paden
- Center for Remote Sensing and Integrated Systems (CReSIS), University of Kansas, Lawrence, KS, USA
| | - Tamara de Riese
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Till Sachau
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Nicolas Stoll
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Now at Department of Environmental Sciences, Informatics and Statistics, Ca'Foscari University Venice, Venice, Italy
| | - Ilka Weikusat
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Frank Wilhelms
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Geoscience Centre, University of Göttingen, Göttingen, Germany
| | - Yu Zhang
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Paul D Bons
- Department of Geosciences, Tübingen University, Tübingen, Germany.
- School of Earth Science and Resources, China University of Geosciences (Beijing), Beijing, China.
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2
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Franke S, Bons PD, Streng K, Mundel F, Binder T, Weikusat I, Bauer CC, Paden JD, Dörr N, Helm V, Steinhage D, Eisen O, Jansen D. Three-dimensional topology dataset of folded radar stratigraphy in northern Greenland. Sci Data 2023; 10:525. [PMID: 37550324 PMCID: PMC10406887 DOI: 10.1038/s41597-023-02339-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 06/27/2023] [Indexed: 08/09/2023] Open
Abstract
We present a dataset of reconstructed three-dimensional (3D) englacial stratigraphic horizons in northern Greenland. The data cover four different regions representing key ice-dynamic settings in Greenland: (i) the onset of Petermann Glacier, (ii) a region upstream of the 79° North Glacier (Nioghalvfjerdsbræ), near the northern Greenland ice divide, (iii) the onset of the Northeast Greenland Ice Stream (NEGIS) and (iv) a 700 km wide region extending across the central ice divide over the entire northern part of central Greenland. In this paper, we promote the advantages of a 3D perspective of deformed englacial stratigraphy and explain how 3D horizons provide an improved basis for interpreting and reconstructing the ice-dynamic history. The 3D horizons are provided in various formats to allow a wide range of applications and reproducibility of results.
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Affiliation(s)
- Steven Franke
- Department of Geosciences, Tübingen University, Tübingen, Germany.
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
| | - Paul D Bons
- Department of Geosciences, Tübingen University, Tübingen, Germany.
- School of Earth Science and Resources, China University of Geosciences, Beijing, China.
| | - Kyra Streng
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Felicitas Mundel
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Tobias Binder
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Ilka Weikusat
- Department of Geosciences, Tübingen University, Tübingen, Germany
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | | | - John D Paden
- Center for Remote Sensing and Integrated Systems (CReSIS), University of Kansas, Lawrence, KS, USA
| | - Nils Dörr
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Veit Helm
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Daniel Steinhage
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Olaf Eisen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, University of Bremen, Bremen, Germany
| | - Daniela Jansen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
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3
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Gerber TA, Lilien DA, Rathmann NM, Franke S, Young TJ, Valero-Delgado F, Ershadi MR, Drews R, Zeising O, Humbert A, Stoll N, Weikusat I, Grinsted A, Hvidberg CS, Jansen D, Miller H, Helm V, Steinhage D, O'Neill C, Paden J, Gogineni SP, Dahl-Jensen D, Eisen O. Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream. Nat Commun 2023; 14:2653. [PMID: 37156772 PMCID: PMC10167229 DOI: 10.1038/s41467-023-38139-8,] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 04/12/2023] [Indexed: 06/28/2024] Open
Abstract
The dynamic mass loss of ice sheets constitutes one of the biggest uncertainties in projections of ice-sheet evolution. One central, understudied aspect of ice flow is how the bulk orientation of the crystal orientation fabric translates to the mechanical anisotropy of ice. Here we show the spatial distribution of the depth-averaged horizontal anisotropy and corresponding directional flow-enhancement factors covering a large area of the Northeast Greenland Ice Stream onset. Our results are based on airborne and ground-based radar surveys, ice-core observations, and numerical ice-flow modelling. They show a strong spatial variability of the horizontal anisotropy and a rapid crystal reorganisation on the order of hundreds of years coinciding with the ice-stream geometry. Compared to isotropic ice, parts of the ice stream are found to be more than one order of magnitude harder for along-flow extension/compression while the shear margins are potentially softened by a factor of two for horizontal-shear deformation.
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Affiliation(s)
- Tamara Annina Gerber
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
| | - David A Lilien
- Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB, Canada
| | - Nicholas Mossor Rathmann
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Steven Franke
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Tun Jan Young
- Scott Polar Research Institute, University of Cambridge, Cambridge, United Kingdom
- School of Geography & Sustainable Development, University of St Andrews, St Andrews, KY16 9AL, United Kingdom
| | - Fernando Valero-Delgado
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - M Reza Ershadi
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Reinhard Drews
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Ole Zeising
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Angelika Humbert
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, University of Bremen, Bremen, Germany
| | - Nicolas Stoll
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, University of Bremen, Bremen, Germany
| | - Ilka Weikusat
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Aslak Grinsted
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Christine Schøtt Hvidberg
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Daniela Jansen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Heinrich Miller
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Veit Helm
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Daniel Steinhage
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | | | - John Paden
- Centre for Remote Sensing and Integrated Systems (CReSIS), University of Kansas, Lawrence, KS, USA
| | | | - Dorthe Dahl-Jensen
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
- Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB, Canada
| | - Olaf Eisen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
- Department of Geosciences, University of Bremen, Bremen, Germany.
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4
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Gerber TA, Lilien DA, Rathmann NM, Franke S, Young TJ, Valero-Delgado F, Ershadi MR, Drews R, Zeising O, Humbert A, Stoll N, Weikusat I, Grinsted A, Hvidberg CS, Jansen D, Miller H, Helm V, Steinhage D, O'Neill C, Paden J, Gogineni SP, Dahl-Jensen D, Eisen O. Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream. Nat Commun 2023; 14:2653. [PMID: 37156772 PMCID: PMC10167229 DOI: 10.1038/s41467-023-38139-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 04/12/2023] [Indexed: 05/10/2023] Open
Abstract
The dynamic mass loss of ice sheets constitutes one of the biggest uncertainties in projections of ice-sheet evolution. One central, understudied aspect of ice flow is how the bulk orientation of the crystal orientation fabric translates to the mechanical anisotropy of ice. Here we show the spatial distribution of the depth-averaged horizontal anisotropy and corresponding directional flow-enhancement factors covering a large area of the Northeast Greenland Ice Stream onset. Our results are based on airborne and ground-based radar surveys, ice-core observations, and numerical ice-flow modelling. They show a strong spatial variability of the horizontal anisotropy and a rapid crystal reorganisation on the order of hundreds of years coinciding with the ice-stream geometry. Compared to isotropic ice, parts of the ice stream are found to be more than one order of magnitude harder for along-flow extension/compression while the shear margins are potentially softened by a factor of two for horizontal-shear deformation.
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Affiliation(s)
- Tamara Annina Gerber
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
| | - David A Lilien
- Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB, Canada
| | - Nicholas Mossor Rathmann
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Steven Franke
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Tun Jan Young
- Scott Polar Research Institute, University of Cambridge, Cambridge, United Kingdom
- School of Geography & Sustainable Development, University of St Andrews, St Andrews, KY16 9AL, United Kingdom
| | - Fernando Valero-Delgado
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - M Reza Ershadi
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Reinhard Drews
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Ole Zeising
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Angelika Humbert
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, University of Bremen, Bremen, Germany
| | - Nicolas Stoll
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, University of Bremen, Bremen, Germany
| | - Ilka Weikusat
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Aslak Grinsted
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Christine Schøtt Hvidberg
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Daniela Jansen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Heinrich Miller
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Veit Helm
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Daniel Steinhage
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | | | - John Paden
- Centre for Remote Sensing and Integrated Systems (CReSIS), University of Kansas, Lawrence, KS, USA
| | | | - Dorthe Dahl-Jensen
- Section for the Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
- Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB, Canada
| | - Olaf Eisen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
- Department of Geosciences, University of Bremen, Bremen, Germany.
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5
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Using MARSIS signal attenuation to assess the presence of South Polar Layered Deposit subglacial brines. Nat Commun 2022; 13:5686. [PMID: 36171186 PMCID: PMC9519933 DOI: 10.1038/s41467-022-33389-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 09/15/2022] [Indexed: 11/08/2022] Open
Abstract
Knowledge of the physical and thermal properties of the South Polar Layer Deposits (SPLD) is key to constrain the source of bright basal reflections at Ultimi Scopuli detected by the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) radar sounder. Here we present a detailed analysis of attenuation, based on data acquired by MARSIS at 3, 4, and 5 MHz. We show that attenuation is frequency dependent, and that its behavior is consistent throughout the entire region. This suggests that the SPLD are compositionally homogeneous at Ultimi Scopuli, and our results are consistent with dust contents of 5 to 12%. Using these values as input, and plausible estimates of surface temperature and heat flux, we inferred basal temperatures around 200 K: these are consistent with perchlorate brines within liquid vein networks as the source of the reflections. Furthermore, extrapolation of the attenuation to higher frequencies explains why SHARAD (Shallow Radar) has thus far not detected basal reflections within the SPLD at Ultimi Scopuli. MARSIS attenuation and thermal data confirm that liquid brines are the most plausible source for the bright reflections at the base of the South Polar Layered Deposits. Such results also justify why SHARAD does not penetrate to the base of the ice.
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6
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Law R, Christoffersen P, Hubbard B, Doyle SH, Chudley TR, Schoonman CM, Bougamont M, des Tombe B, Schilperoort B, Kechavarzi C, Booth A, Young TJ. Thermodynamics of a fast-moving Greenlandic outlet glacier revealed by fiber-optic distributed temperature sensing. SCIENCE ADVANCES 2021; 7:7/20/eabe7136. [PMID: 33990322 PMCID: PMC8121432 DOI: 10.1126/sciadv.abe7136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 03/26/2021] [Indexed: 06/12/2023]
Abstract
Measurements of ice temperature provide crucial constraints on ice viscosity and the thermodynamic processes occurring within a glacier. However, such measurements are presently limited by a small number of relatively coarse-spatial-resolution borehole records, especially for ice sheets. Here, we advance our understanding of glacier thermodynamics with an exceptionally high-vertical-resolution (~0.65 m), distributed-fiber-optic temperature-sensing profile from a 1043-m borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland. We report substantial but isolated strain heating within interglacial-phase ice at 208 to 242 m depth together with strongly heterogeneous ice deformation in glacial-phase ice below 889 m. We also observe a high-strain interface between glacial- and interglacial-phase ice and a 73-m-thick temperate basal layer, interpreted as locally formed and important for the glacier's fast motion. These findings demonstrate notable spatial heterogeneity, both vertically and at the catchment scale, in the conditions facilitating the fast motion of marine-terminating glaciers in Greenland.
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Affiliation(s)
- Robert Law
- Scott Polar Research Institute, University of Cambridge, Cambridge, UK.
| | | | - Bryn Hubbard
- Centre for Glaciology, Aberystwyth University, Aberystwyth, UK
| | - Samuel H Doyle
- Centre for Glaciology, Aberystwyth University, Aberystwyth, UK
| | - Thomas R Chudley
- Scott Polar Research Institute, University of Cambridge, Cambridge, UK
| | | | - Marion Bougamont
- Scott Polar Research Institute, University of Cambridge, Cambridge, UK
| | - Bas des Tombe
- Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, Netherlands
| | - Bart Schilperoort
- Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, Netherlands
| | - Cedric Kechavarzi
- Centre for Smart Infrastructure and Construction, Department of Engineering, University of Cambridge, Cambridge, UK
| | - Adam Booth
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - Tun Jan Young
- Scott Polar Research Institute, University of Cambridge, Cambridge, UK
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7
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Maier N, Humphrey N, Harper J, Meierbachtol T. Sliding dominates slow-flowing margin regions, Greenland Ice Sheet. SCIENCE ADVANCES 2019; 5:eaaw5406. [PMID: 31309154 PMCID: PMC6620096 DOI: 10.1126/sciadv.aaw5406] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 06/06/2019] [Indexed: 06/10/2023]
Abstract
On the Greenland Ice Sheet (GrIS), ice flow due to deformation and sliding across the bed delivers ice to lower-elevation marginal regions where it can melt. We measured the two mechanisms of motion using a three-dimensional array of 212 tilt sensors installed within a network of boreholes drilled to the bed in the ablation zone of GrIS. Unexpectedly, sliding completely dominates ice motion all winter, despite a hard bedrock substrate and no concurrent surface meltwater forcing. Modeling constrained by detailed tilt observations made along the basal interface suggests that the high sliding is due to a slippery bed, where sparsely spaced bedrock bumps provide the limited resistance to sliding. The conditions at the site are characterized as typical of ice sheet margins; thus, most ice flow near the margins of GrIS is mainly from sliding, and marginal ice fluxes are near their theoretical maximum for observed surface speeds.
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Affiliation(s)
- Nathan Maier
- Department of Geology and Geophysics, University of Wyoming, Laramie, WY, USA
| | - Neil Humphrey
- Department of Geology and Geophysics, University of Wyoming, Laramie, WY, USA
| | - Joel Harper
- Geosciences Department, University of Montana, Missoula, MT, USA
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8
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Goelzer H, Nowicki S, Edwards T, Beckley M, Abe-Ouchi A, Aschwanden A, Calov R, Gagliardini O, Gillet-Chaulet F, Golledge NR, Gregory J, Greve R, Humbert A, Huybrechts P, Kennedy JH, Larour E, Lipscomb WH, clećh SL, Lee V, Morlighem M, Pattyn F, Payne AJ, Rodehacke C, Rückamp M, Saito F, Schlegel N, Seroussi H, Shepherd A, Sun S, van de Wal R, Ziemen FA. Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison. THE CRYOSPHERE 2019; 12:1433-1460. [PMID: 32676174 PMCID: PMC7365265 DOI: 10.5194/tc-12-1433-2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Earlier large-scale Greenland ice sheet sea-level projections (e.g., those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of the initMIP-Greenland intercomparison exercise is to compare, evaluate and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercomparison Project - phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of 1) the initial present-day state of the ice sheet and 2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly), and should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap, but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.
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Affiliation(s)
- Heiko Goelzer
- Utrecht University, Institute for Marine and Atmospheric Research (IMAU), Utrecht, Netherlands
- Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium
| | | | - Tamsin Edwards
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, United Kingdom
| | | | - Ayako Abe-Ouchi
- Atmosphere Ocean Research Institute, University of Tokyo, Kashiwa, Japan
| | | | - Reinhard Calov
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - Olivier Gagliardini
- Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, F-38000 Grenoble, France
| | | | - Nicholas R. Golledge
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand
| | - Jonathan Gregory
- Department of Meteorology, University of Reading, Reading, United Kingdom
- Met Office Hadley Center, Exeter, United Kingdom
| | - Ralf Greve
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - Angelika Humbert
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
- University of Bremen, Bremen, Germany
| | | | - Joseph H. Kennedy
- Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, USA
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, USA
| | - Eric Larour
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
| | - William H. Lipscomb
- Los Alamos National Laboratory, Los Alamos, USA
- National Center for Atmospheric Research, Boulder, USA
| | - Sébastien Le clećh
- LSCE/IPSL, Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
| | | | | | - Frank Pattyn
- Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium
| | | | - Christian Rodehacke
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
- Danish Meteorological Institute, Copenhagen, Denmark
| | - Martin Rückamp
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
| | - Fuyuki Saito
- Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
| | - Nicole Schlegel
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
| | - Helene Seroussi
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
| | - Andrew Shepherd
- School of Earth and Environment, University of Leeds, United Kingdom
| | - Sainan Sun
- Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium
| | - Roderik van de Wal
- Utrecht University, Institute for Marine and Atmospheric Research (IMAU), Utrecht, Netherlands
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9
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Basal freeze-on generates complex ice-sheet stratigraphy. Nat Commun 2018; 9:4669. [PMID: 30405102 PMCID: PMC6220257 DOI: 10.1038/s41467-018-07083-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 10/15/2018] [Indexed: 11/18/2022] Open
Abstract
Large, plume-like internal ice-layer-structures have been observed in radar images from both Antarctica and Greenland, rising from the ice-sheet base to up to half of the ice thickness. Their origins are not yet understood. Here, we simulate their genesis by basal freeze-on using numerical ice-flow modelling and analyse the transient evolution of the emerging ice-plume and the surrounding ice-layer structure as a function of both freeze-on rate and ice flux. We find good agreement between radar observations, modelled ice-plume geometry and internal layer structure, and further show that plume height relates primarily to ice-flux and only secondarily to freeze-on. An in-depth analysis, performed for Northern Greenland of observed spatial plume distribution related to ice flow, basal topography and water availability supports our findings regarding ice flux and suggests freeze-on is controlled by ascending subglacial water flow. Our results imply that widespread basal freeze-on strongly affects ice stratigraphy and consequently ice-core interpretations. Subsurface ice-sheet radar images reveal large plume-shaped bodies rising from the base, with their origin not yet understood. Here, the authors show that freeze-on of water at the ice-sheet base combined with ice-flux explains the vertical extent, shape and structure of the observed plumes.
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Kjær KH, Larsen NK, Binder T, Bjørk AA, Eisen O, Fahnestock MA, Funder S, Garde AA, Haack H, Helm V, Houmark-Nielsen M, Kjeldsen KK, Khan SA, Machguth H, McDonald I, Morlighem M, Mouginot J, Paden JD, Waight TE, Weikusat C, Willerslev E, MacGregor JA. A large impact crater beneath Hiawatha Glacier in northwest Greenland. SCIENCE ADVANCES 2018; 4:eaar8173. [PMID: 30443592 PMCID: PMC6235527 DOI: 10.1126/sciadv.aar8173] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 10/09/2018] [Indexed: 05/11/2023]
Abstract
We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impact-related grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet.
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Affiliation(s)
- Kurt H. Kjær
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
- Corresponding author.
| | - Nicolaj K. Larsen
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
- Department of Geoscience, Aarhus University, Aarhus, Denmark
| | - Tobias Binder
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Anders A. Bjørk
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
- Department of Earth System Science, University of California, Irvine, Irvine, CA, USA
- NASA Jet Propulsion Lab, Pasadena, CA, USA
| | - Olaf Eisen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Department of Geosciences, University of Bremen, Bremen, Germany
| | - Mark A. Fahnestock
- Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA
| | - Svend Funder
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
| | - Adam A. Garde
- Geological Survey of Denmark and Greenland, Copenhagen, Denmark
| | - Henning Haack
- Maine Mineral and Gem Museum, Bethel, ME, USA
- Geobiology and Minerals Section, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
| | - Veit Helm
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Michael Houmark-Nielsen
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
| | - Kristian K. Kjeldsen
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
- Geological Survey of Denmark and Greenland, Copenhagen, Denmark
- Department of Earth Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Shfaqat A. Khan
- DTU Space, National Space Institute, Department of Geodesy, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Horst Machguth
- Department of Geosciences, University of Fribourg, Fribourg, Switzerland
- Department of Geography, University of Zurich, Zurich, Switzerland
| | - Iain McDonald
- School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff, UK
| | - Mathieu Morlighem
- Department of Earth System Science, University of California, Irvine, Irvine, CA, USA
| | - Jérémie Mouginot
- Department of Earth System Science, University of California, Irvine, Irvine, CA, USA
- Université Grenoble Alpes, CNRS, INP, Grenoble, France
| | - John D. Paden
- Center for Remote Sensing of Ice Sheets, University of Kansas, Lawrence, KS, USA
| | - Tod E. Waight
- Department of Geosciences and Natural Resources Management (Geology Section), University of Copenhagen, Copenhagen, Denmark
| | - Christian Weikusat
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Eske Willerslev
- Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
- Department of Zoology, University of Cambridge, Cambridge, UK
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Joseph A. MacGregor
- Cryospheric Sciences Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA
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A New Method for Automatically Tracing Englacial Layers from MCoRDS Data in NW Greenland. REMOTE SENSING 2017. [DOI: 10.3390/rs10010043] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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12
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Goelzer H, Robinson A, Seroussi H, van de Wal RSW. Recent Progress in Greenland Ice Sheet Modelling. CURRENT CLIMATE CHANGE REPORTS 2017; 3:291-302. [PMID: 32010550 PMCID: PMC6959375 DOI: 10.1007/s40641-017-0073-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
PURPOSE OF REVIEW This paper reviews the recent literature on numerical modelling of the dynamics of the Greenland ice sheet with the goal of providing an overview of advancements and to highlight important directions of future research. In particular, the review is focused on large-scale modelling of the ice sheet, including future projections, model parameterisations, paleo applications and coupling with models of other components of the Earth system. RECENT FINDINGS Data assimilation techniques have been used to improve the reliability of model simulations of the Greenland ice sheet dynamics, including more accurate initial states, more comprehensive use of remote sensing as well as paleo observations and inclusion of additional physical processes. SUMMARY Modellers now leverage the increasing number of high-resolution satellite and air-borne data products to initialise ice sheet models for centennial time-scale simulations, needed for policy relevant sea-level projections. Modelling long-term past and future ice sheet evolution, which requires simplified but adequate representations of the interactions with the other components of the Earth system, has seen a steady improvement. Important developments are underway to include ice sheets in climate models that may lead to routine simulation of the fully coupled Greenland ice sheet-climate system in the coming years.
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Affiliation(s)
- Heiko Goelzer
- 1Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
- 2Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium
| | - Alexander Robinson
- 3Faculty of Geology and Geoenvironment, University of Athens, 15784 Athens, Greece
- 4Universidad Complutense de Madrid, 28040 Madrid, Spain
- 5Instituto de Geociencias, UCM-CSIC, 28040 Madrid, Spain
| | - Helene Seroussi
- 6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA
| | - Roderik S W van de Wal
- 1Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
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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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Converging flow and anisotropy cause large-scale folding in Greenland's ice sheet. Nat Commun 2016; 7:11427. [PMID: 27126274 PMCID: PMC4855532 DOI: 10.1038/ncomms11427] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 03/24/2016] [Indexed: 11/27/2022] Open
Abstract
The increasing catalogue of high-quality ice-penetrating radar data provides a unique insight in the internal layering architecture of the Greenland ice sheet. The stratigraphy, an indicator of past deformation, highlights irregularities in ice flow and reveals large perturbations without obvious links to bedrock shape. In this work, to establish a new conceptual model for the formation process, we analysed the radar data at the onset of the Petermann Glacier, North Greenland, and created a three-dimensional model of several distinct stratigraphic layers. We demonstrate that the dominant structures are cylindrical folds sub-parallel to the ice flow. By numerical modelling, we show that these folds can be formed by lateral compression of mechanically anisotropic ice, while a general viscosity contrast between layers would not lead to folding for the same boundary conditions. We conclude that the folds primarily form by converging flow as the mechanically anisotropic ice is channelled towards the glacier. A range of mechanisms has been proposed for large-scale folding in polar ice sheets. Here, using new three-dimensional reconstructions of such folds in the onset region of the Greenland Petermann Glacier, the authors show that these formed due to flow convergence and the high mechanical anisotropy of ice.
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MacGregor JA, Colgan WT, Fahnestock MA, Morlighem M, Catania GA, Paden JD, Gogineni SP. Holocene deceleration of the Greenland Ice Sheet. Science 2016; 351:590-3. [PMID: 26912699 DOI: 10.1126/science.aab1702] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 01/07/2016] [Indexed: 11/02/2022]
Abstract
Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet's radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet's dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.
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Affiliation(s)
- Joseph A MacGregor
- Institute for Geophysics, The University of Texas at Austin, Austin, TX 78758, USA.
| | - William T Colgan
- Geological Survey of Denmark and Greenland, Copenhagen DK-1350, Denmark
| | - Mark A Fahnestock
- Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Mathieu Morlighem
- Department of Earth System Science, University of California, Irvine, Irvine, CA 92697, USA
| | - Ginny A Catania
- Institute for Geophysics, The University of Texas at Austin, Austin, TX 78758, USA. Department of Geological Sciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - John D Paden
- Center for Remote Sensing of Ice Sheets, The University of Kansas, Lawrence, KS 66045, USA
| | - S Prasad Gogineni
- Center for Remote Sensing of Ice Sheets, The University of Kansas, Lawrence, KS 66045, USA
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Hvidberg CS. Ice sheet in peril. Science 2016; 351:562-3. [DOI: 10.1126/science.aad9997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Radar data reveal how sensitive the Greenland Ice Sheet is to long-term climatic changes
[Also see Report by
MacGregor
et al.
]
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Affiliation(s)
- Christine S. Hvidberg
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
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