Future surface mass balance and surface melt in the Amundsen sector of the West Antarctic Ice Sheet

• Published in: The Cryosphere
• Main Authors: Donat-Magnin, Marion, Jourdain, Nicolas, Kittel, Christoph, Agosta, Cécile, Amory, Charles, Gallée, Hubert, Krinner, Gerhard, Chekki, Mondher
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), 869304 Horizon 2020 Framework Programme, H2020 Agence Nationale de la Recherche, ANR: ANR-15-CE01-0005-01, Acknowledgements. The present work is a contribution to the TROIS-AS project, and is PROTECT contribution number 6. All the computations presented in this paper were performed using the GRICAD infrastructure (https://gricad.univ-grenoble-alpes.fr, last access: 20 January 2021), which is supported by Grenoble research communities., ANR-15-CE01-0005,TROIS-AS,Vers un système de modélisation régionale océan / calotte / atmosphère(2015)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU]Sciences of the Universe [physics]; Antarc*; Antarctic; Ice Sheet; Ice Shelf; Ice Shelves; Sea ice; The Cryosphere
• Online Access: https://hal.science/hal-03162095; https://hal.science/hal-03162095/document; https://hal.science/hal-03162095/file/tc-15-571-2021.pdf; https://doi.org/10.5194/tc-15-571-2021

International audience We present projections of West Antarctic surface mass balance (SMB) and surface melt to 2080 2100 under the RCP8.5 scenario and based on a regional model at 10 km resolution. Our projections are built by adding a CMIP5 (Coupled Model Intercomparison Project Phase 5) multi-model-mean seasonal climate-change anomaly to the present-day model boundary conditions. Using an anomaly has the advantage to reduce CMIP5 model biases, and a perfect-model test reveals that our approach captures most characteristics of future changes despite a 16 % 17 % underestimation of projected SMB and melt rates. SMB over the grounded ice sheet in the sector between Getz and Abbot increases from 336 Gtyr-1 in 1989 2009 to 455 Gtyr-1 in 2080 2100, which would reduce the global sea level changing rate by 0.33 mmyr-1. Snowfall indeed increases by 7.4 % °C-1 to 8.9 % °C-1 of near-surface warming due to increasing saturation water vapour pressure in warmer conditions, reduced sea-ice concentrations, and more marine air intrusion. Ice-shelf surface melt rates increase by an order of magnitude in the 21st century mostly due to higher downward radiation from increased humidity and to reduced albedo in the presence of melting. There is a net production of surface liquid water over eastern ice shelves (Abbot, Cosgrove, and Pine Island) but not over western ice shelves (Thwaites, Crosson, Dotson, and Getz). This is explained by the evolution of the melt-to-snowfall ratio: below a threshold of 0.60 to 0.85 in our simulations, firn air is not entirely depleted by melt water, while entire depletion and net production of surface liquid water occur for higher ratios. This suggests that western ice shelves might remain unaffected by hydrofracturing for more than a century under RCP8.5, while eastern ice shelves have a high potential for hydrofracturing before the end of this century.