Influence of Small-Scale Processes on the Coupled Atmosphere-Cryosphere-Ocean System in Adélie Land, Antarctica

This PhD project investigated how small-scale processes (typical length scales below 100 km) shape the interactions between the ocean, sea ice, ice sheet and atmosphere in Antarctica, focusing on the Adélie Land region. Using the regional climate model MAR (Modèle Atmosphérique Régional), the work first assessed the sensitivity of the Antarctic surface mass balance (SMB) to present and future ocean and sea ice conditions, showing that katabatic winds and temperature inversions largely shield the ice sheet from ocean-driven perturbations. Building on this, an ensemble of MAR simulations forced by CMIP5/CMIP6 models projected a contrasting future SMB response: increasing over the grounded ice sheet due to stronger snowfall, but decreasing over the ice shelves due to enhanced meltwater runoff — with a sharp SMB decline projected above +2.5°C of Antarctic warming. A follow-up study identified cloud phase, particularly liquid-containing clouds, as a major driver of uncertainty in future ice shelf melt through the snow-melt-albedo feedback. The thesis also used ocean and coupled ocean-sea ice-atmosphere modelling (NEMO-LIM coupled with MAR) to show that ice shelf basal melt is strongly amplified by tides and reshapes dense water formation off Adélie Land, that atmospheric forcing resolution significantly affects coastal polynya activity and sea ice production, and that ocean mesoscale eddies measurably modulate atmosphere-sea ice-ocean heat and momentum exchanges.