Firn air content changes on Antarctic ice shelves under three future warming scenarios

• Published in: The Cryosphere
• Main Authors: Veldhuijsen, Sanne B. M., van de Berg, Willem Jan, Kuipers Munneke, Peter, van den Broeke, Michiel R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: article; Verlagsveröffentlichung; Antarctic; The Antarctic; Antarctic Peninsula; Dronning Maud Land; Roi Baudouin; Antarc*; Ice Shelf; Ice Shelves; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-18-1983-2024; https://noa.gwlb.de/receive/cop_mods_00073294; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00071470/tc-18-1983-2024.pdf; https://tc.copernicus.org/articles/18/1983/2024/tc-18-1983-2024.pdf

The Antarctic firn layer provides pore space in which an estimated 94 % to 96 % of the surface melt refreezes or is retained as liquid water. Future depletion of firn pore space by increased surface melt, densification and formation of low-permeability ice slabs can potentially lead to meltwater ponding, hydrofracturing and ice-shelf disintegration. Here, we investigate the 21st-century evolution of total firn air content (FAC) and accessible FAC (i.e. the pore space that meltwater can reach) across Antarctic ice shelves. We use the semi-empirical IMAU Firn Densification Model (IMAU-FDM) with an updated dynamical densification expression to cope with changing climate forcing. The firn model is forced by general circulation model output of the Community Earth System Model version 2 (CESM2) for three climate emission scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5), dynamically downscaled to a 27 km horizontal resolution by the Regional Atmospheric Climate Model version 2.3p2 (RACMO2.3p2). To estimate accessible FAC, we prescribe a relationship between ice-slab thickness and permeability. In our simulations, ice shelves on the Antarctic Peninsula and the Roi Baudouin Ice Shelf in Dronning Maud Land are particularly vulnerable to total FAC depletion (> 50 % decrease by 2100), even for low-emission (SSP1-2.6) and intermediate-emission (SSP2-4.5) scenarios. In the high-emission (SSP5-8.5) scenario in particular, the formation of ice slabs further reduces accessible FAC on ice shelves with low accumulation rates (current rates of < 500 mmw.e.yr-1), including many East Antarctic ice shelves and the Filchner–Ronne, Ross, Pine Island and Larsen C ice shelves. These results underline the potentially large vulnerability of low-accumulation ice shelves to firn air depletion through ice-slab formation.