Is a warming of the Antarctic continental shelf reversible?

IPCC-AR4 scenario forced simulations with the coupled sea ice - ice shelf - ocean models (BRIOS and FESOM) show a strong sensitivity of the southern Weddell Sea to the freshwater fluxes resulting from the atmospheric forcing and related sea ice formation. As a consequence of continues freshening during the 21st century the slope current changes course into the Filchner Trough and underneath the Filchner-Ronne Ice Shelf affecting its basal mass flux and the ice shelf/ice sheet dynamics. As a follow-up, we investigate the possibility for a system return to present conditions with saline continental shelf waters at the surface freezing point and the slope current following the shelf break westwards. It turns out that starting from year 2199, 20th-century atmospheric forcing reduces the Filchner-Ronne basal mass loss by 50%, though still 10 times the present value of 80 Gt/a. However, prescribing a mean 20th-century basal melt water flux reverses the hydrography of the southern Weddell Sea to present conditions within less than a decade. The importance of basal melt water for the system is evident also by the fact that prescribing the mean 20th-century basal fluxes starting in 2050 does not allow the coastal current to penetrate into the Filchner Trough. Our study shows that once the system reached the 'warm state' only a cooling of the open ocean waters - less feasible in a warming climate - or a significant reduction of basal melting would stop warm waters from entering the continental shelf. The latter, however, is related to a significant reduction of the ice shelf basal area