The circum-Antarctic ice-shelves respond to a more positive Southern Annular Mode with regionally varied melting

Abstract

AbstractThe Southern Hemisphere cryosphere has recently shown regionally-contrasted responses to climate change, in particular to the positive phases of the Southern Annular Mode. However, the understanding of the impacts of this mode on ice-shelf basal melt at a circum-Antarctic scale is still limited. Here, we performed idealized experiments with a pan-Antarctic regional ice-shelf cavity-resolving ocean—sea-ice model for different phases of the Southern Annular Mode. We show that positive phases lead to increased upwelling and subsurface ocean temperature and salinity close to ice shelves, while the opposite occurs for negative phases. A one-standard-deviation increase of the Southern Annular Mode leads to a net basal mass loss of 40 Gt yr−1, with strong regional contrasts: increased ice-shelf basal melt in the Bellingshausen and Western Pacific sectors and the opposite response in the Amundsen sector. Estimates of 1000–1200 and 2090–2100 ice-shelf basal melt changes due to the Southern Annular Mode are −86.6 Gt yr−1 and 55.0 to 164.9 Gt yr−1, respectively, compared to the present.