Improving Understanding of Future Antarctic Ice-Shelf Vulnerability to Atmospheric Warming

Abstract:

Antarctic Ice Sheet mass loss is mitigated by ice shelves, which surround approximately 75% of the continent and regulate ice flow by buttressing upstream tributary glaciers. Ice-shelf stability is threatened by ponding meltwater, which percolates and refreezes in the firn, decreasing the firn’s capacity to store future meltwater. Depleted firn air content may lead to increased rates of hydrofracture, a process by which meltwater drains rapidly through vertical fractures. For example, in 2002 the Larsen B ice shelf disintegrated driven by hundreds of lake drainage events via hydrofracture. This event prompted concern regarding the fate of Antarctica’s remaining ice shelves. Here, we use a sophisticated snow model (SNOWPACK) driven by a transient Earth System Model (CESM2, 1850-2100) to investigate the historic and future evolution of firn conditions across Antarctic ice shelves. By analyzing atmospheric conditions, we establish relationships between firn air depletion and the processes that drive it. We show that under a high emissions scenario, many ice shelves may reach a tipping point by the end of this century, resulting in firn that is incapable of absorbing additional meltwater, exacerbating the risk of hydrofracture and increasing the vulnerability of ice shelves to collapse.