Present and future sensitivity of the Antarctic surface mass balance to oceanic and atmospheric forcings: insights with the regional climate model MAR

• Main Author: Kittel, Christoph
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: ULiège - Université de Liège 2021
• Subjects: Antarcc; SMB; sensitivity; ocean; atmosphere; projection; climate warming; Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Antarctic; The Antarctic; Antarc*; Antarctica; Ice Sheet; Ice Shelves; Sea ice
• Online Access: https://orbi.uliege.be/handle/2268/258491; https://orbi.uliege.be/bitstream/2268/258491/1/thesis_ckittel.pdf

Recent Global Warming has caused widespread ice losses from the Antarctic Ice Sheet (AIS) leading to an increase in mean sea level. By influencing the ice dynamics and the mass of water that accumulates on the continent, the surface mass balance (SMB, i.e, the difference between snow accumulation and ablation at the surface of the ice sheet) contributes to sea-level variations. A better knowledge of how present and future SMB will change is therefore needed to refine sea-level-rise estimates. With the aim of identifying the driving processes from different components of the climate system (from the surface of the ocean to high-elevation clouds), we reconstruct and project the Antarctic SMB using the regional climate model MAR developed at ULiège, over 1980--2100. The results of MAR have been first compared to diverse observations to evaluate its performance. We gathered observations of several types (near-surface climate and snow accumulation) to guarantee the robustness of our results and conclusions based on our climate modeling. A first objective of this thesis was to determine to what extent the recent changes at the ocean surface can exert a direct feedback on the atmosphere and SMB. Our simulations with perturbed sea-ice concentration and sea-surface temperature around Antarctica reveal that strong and persistent katabatic winds prevent most atmospheric changes induced by the ocean to penetrate inland. This suggests a limited influence of the ocean surface on the Antarctic SMB. We focused afterwards on the sensitivity of the SMB to atmospheric warmings projected by global models using high-emission scenarios (RCP8.5 and ssp585). Higher temperatures are projected to increase SMB on the grounded ice as a result of stronger snowfall while the future SMB over the ice shelves should be dominated by higher meltwater-runoff values (compromising the stability of ice shelves) and is consequently projected to decrease. Leaving aside the role of the ocean on the thinning of ice shelves, increasing surface melt should ...