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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/tc-2020-28
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2020-28
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  10 Mar 2020

10 Mar 2020

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This preprint is currently under review for the journal TC.

Exploring the impact of atmospheric forcing and basal boundary conditions on the simulation of the Antarctic ice sheet at the Last Glacial Maximum

Javier Blasco1,2, Jorge Alvarez-Solas1,2, Alexander Robinson1,2,3, and Marisa Montoya1,2 Javier Blasco et al.
  • 1Departamento de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, Facultad de Ciencias Físicas, 28040 Madrid, Spain
  • 2Instituto de Geociencias, Consejo Superior de Investigaciones Cientifícas-Universidad Complutense de Madrid, 28040 Madrid, Spain
  • 3Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany

Abstract. Little is known about the distribution of ice in the Antarctic ice sheet (AIS) during the Last Glacial Maximum (LGM). Whereas marine and terrestrial geological data indicate that the grounded ice advanced to a position close to the continental-shelf break, the total ice volume is unclear. Glacial boundary conditions are potentially important sources of uncertainty, in particular basal friction and climatic boundary conditions. Basal friction exerts a strong control on the large-scale dynamics of the ice sheet and thus affects its size, and is not well constrained. Glacial climatic boundary conditions determine the net accumulation and ice temperature, and are also poorly known. Here we explore the effect of the uncertainty in both features on the total simulated ice storage of the AIS at the LGM. For this purpose we use a hybrid ice-sheet-shelf model that is forced with different basal-drag choices and glacial background climatic conditions obtained from the LGM ensemble climate simulations of the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). For a wide range of plausible basal friction configurations, the simulated ice dynamics vary widely but all simulations produce fully extended ice sheets towards the continental-shelf break. More dynamically active ice sheets correspond to lower ice volumes, while they remain consistent with the available constraints on ice extent. Thus, this work points to the possibility of an AIS with very active ice streams during the LGM. In addition, we find that the surface boundary temperature field plays a crucial role in determining the ice extent through its effect on viscosity. For ice sheets of a similar extent and comparable dynamics, we find that the precipitation field determines the total AIS volume. However, precipitation is deeply uncertain. Climatic fields simulated by climate models show more precipitation in coastal regions than a spatially uniform anomaly, which can lead to larger ice volumes. We strongly support using these paleoclimatic fields to simulate and study the LGM and potentially other time periods like the Last Interglacial. However, their accuracy must be assessed as well, as differences between climate model forcing lead to a range in the simulated ice volume and extension of about 6 m sea-level equivalent and one million km2.

Javier Blasco et al.

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Javier Blasco et al.

Data sets

LGM AIS from PMIP3 repository Javier Blasco Alexander Robinson Jorge Alvarez-Solas Marisa Montoya https://doi.org/10.5281/zenodo.3701258

Model code and software

palma-ice/yelmo: Beta version for archiving at Zenodo. Alexander Robinson Jorge Alvarez-Solas Marisa Montoya https://doi.org/10.5281/zenodo.3443654

Javier Blasco et al.

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Latest update: 21 Oct 2020
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Short summary
During the LGM the Antarctic ice sheet was larger and more extended than PD. However, neither its exact position nor the total ice volume are well constrained. Here we investigate how the different climatic boundary conditions, as well as basal friction configurations, affect the size and extent of the Antarctic ice sheet and discuss its potential implications.
During the LGM the Antarctic ice sheet was larger and more extended than PD. However, neither...
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