Observed interannual changes beneath Filchner-Ronne Ice Shelf linked to large-scale atmospheric circulation

Tore Hattermann,Markus A Janout,Peter E D Davis,Elisabeth Schlosser,Hartmut H Hellmer,Keith W Nicholls,Gerd Rohardt,Svein Østerhus,Torsten Kanzow

doi:10.1038/s41467-021-23131-x

Abstract

Floating ice shelves are the Achilles’ heel of the Antarctic Ice Sheet. They limit Antarctica’s contribution to global sea level rise, yet they can be rapidly melted from beneath by a warming ocean. At Filchner-Ronne Ice Shelf, a decline in sea ice formation may increase basal melt rates and accelerate marine ice sheet mass loss within this century. However, the understanding of this tipping-point behavior largely relies on numerical models. Our new multi-annual observations from five hot-water drilled boreholes through Filchner-Ronne Ice Shelf show that since 2015 there has been an intensification of the density-driven ice shelf cavity-wide circulation in response to reinforced wind-driven sea ice formation in the Ronne polynya. Enhanced southerly winds over Ronne Ice Shelf coincide with westward displacements of the Amundsen Sea Low position, connecting the cavity circulation with changes in large-scale atmospheric circulation patterns as a new aspect of the atmosphere-ocean-ice shelf system.

Highlights

Floating ice shelves are the Achilles’ heel of the Antarctic Ice Sheet
Similar source water salinities are observed at the southern Filchner drill sites (Figs. 1 and 2c; FSW & FSE) and relate to denser Ronne High Salinity Shelf Water (HSSW) that is typically found in the southwestern Weddell Sea
Our new multi-annual oceanographic time series beneath Filchner-Ronne Ice Shelf show that recently intensified sea ice formation in the southern Weddell Sea has reinforced the cavitywide buoyancy-driven circulation (Ronne mode) that maintains the dense water outflow in the Filchner Trough

Summary

Introduction

Floating ice shelves are the Achilles’ heel of the Antarctic Ice Sheet. They limit Antarctica’s contribution to global sea level rise, yet they can be rapidly melted from beneath by a warming ocean. At Filchner-Ronne Ice Shelf, a decline in sea ice formation may increase basal melt rates and accelerate marine ice sheet mass loss within this century. Observations indicate that FRIS is vulnerable to warmer inflows[7], and modeling studies suggest that FRIS may exhibit a tipping-point behavior, with the potential for an order-of-magnitude increase in basal melt rates[8,9] that might have profound impacts, within this century, on the ice sheet and dense water formation in this region[10]. ISW is primarily exported from beneath FRIS through the Filchner Trough[15,16] that connects the ice shelf cavity with the deep ocean At present, these outflows are dense enough to block the inflow of. The uncertainties in these projections are large[19] and the likelihood of such a regime shift due to ongoing climate change remains largely unknown

Methods

Results

Conclusion