Sensitivity of Ross Ice Shelf, Antarctica, to Changing Climate

Ross Ice Shelf (RIS) is the largest ice shelf in Antarctica, and is fed by ice from both the West and East Antarctic Ice Sheets (WAIS and EAIS). The RIS is presently fairly stable; however, if future climates states were to cause a reduction in ice-shelf mass, then buttressing of grounded ice would also decrease, accelerating the ice sheets’ contributions to sea level rise. This motivates us to improve our understanding of the sensitivity of RIS mass to atmospheric and oceanic variability, and to explore how RIS mass loss affects the adjacent grounded ice sheet.

We use satellite altimetry measurements over the last two decades to describe temporal and spatial variability in RIS thickness, and ocean measurements and models, and atmospheric reanalysis products to assess the causes of observed thickness variability.  We define three regions of RIS based on their sensitivity to atmospheric and oceanic processes: the Ice Shelf Frontal Zone (ISFZ); interior RIS-EAIS; and interior RIS-WAIS. The ISFZ is influenced by proximity to open water and sensitive to changes in summer upper-ocean heating in the Ross Polynya, a region of relatively sea-ice-free water just north of the RIS front. Interannual changes in snowfall play a significant role in changing thickness of the RIS interior regions: these changes appear to be correlated with the Southern Oscillation Index (SOI) through changing wind patterns as the Amundsen Low varies in location and intensity.

Idealized simulations with an ice-sheet model show that accelerated basal melting associated with future intrusions of warm water under the WAIS side of RIS could lead to substantial grounding line retreat and grounded-ice mass loss. These losses contribute >10 cm of sea level rise over centuries. Perhaps more importantly, recent studies have shown that reshaping the ice-sheet topography alters the regional atmospheric circulation, which may affect the mass balance of the adjacent Amundsen Sea sector through the surface mass balance, and by modifying the ocean circulation changing basal melt rates. Our results point the need to study not only the glacier systems currently experiencing rapid retreat, but also neighboring ice-shelf/glacier systems whose variability can affect larger-scale ice-sheet stability through atmospheric and oceanic teleconnections.