Strong ice-ocean interaction drives and enhances calving of Antarctic ice shelves

Abstract

Since 2015, there has been a significant increase in iceberg calving rates from Antarctic ice shelves. It is crucial to comprehend the climate-related reasons for this enhanced iceberg calving to improve coupled simulations with the ice sheet and predict their future effects on sea-level rise. Based on continuous observations of iceberg calving around Antarctica over 15 years, we demonstrate that sea ice extent is the primary control on iceberg calving rates in Antarctica, regardless of ice shelf size, location, or ocean regime. The recent increase in calving rates coincides precisely with a significant reduction in sea ice area in most sectors around the continent. We propose a calving model, where iceberg calving is dominated by ocean-wave induced flexure and basal shear and enhanced by ice-shelf basal melt. We also find links between iceberg calving rate and El Niño/Southern Oscillation (ENSO), which are particularly strong in East Antarctica. Given that further decreases in sea ice extent and increases in extreme ENSO events are predicted in future, we raise concern that previously stable East Antarctic ice shelves may soon begin to retreat, with potential to trigger significant mass loss from this massive ice sheet.