Antarctic surface hydrology and its impact on ice-sheet mass balance

Presenter: Jonathan Kingslake (LDEO)

Abstract:
Surface meltwater potentially poses a threat to the floating ice shelves that partially surround the Antarctic Ice Sheet. Brittle fractures in the surface of the ice are thought to be generated and enlarged when surface meltwater ponds in surface depressions, potentially triggering rapid ice-shelf collapse. Where ice shelves slow the flow of the grounded ice sheet, collapse leads to acceleration and thinning of upstream glaciers and increases sea-level rise. A concern is that future increases in melting caused by atmospheric warming could trigger ice-shelf collapse and accelerate sea-level rise. I will introduce these processes and present outcomes of an interdisciplinary workshop held on this topic at Lamont-Doherty Earth Observatory. I will present a simple framework, emerging from the workshop, for focusing efforts to quantify the impact of Antarctic surface melting on sea-level rise. I will then describe results from ongoing projects aimed at quantifying (1) how hydrology controls which parts of the ice shelves receive significant quantities of meltwater, and (2) which regions are vulnerable to collapse triggered by meltwater. These results draw on high-resolution satellite imagery and digital elevation models, models of vertical fracture propagation, and continent-wide strain-rate fields. We highlight locations where vulnerable areas lie downstream of drainage systems that seasonally grow to different lengths in different years. Drainage-system growth depends on seasonal melt volumes and, potentially, on multi-year evolution of the ice-shelf surface. We require a deeper understanding of these systems if we are to improve predictions of where meltwater will be delivered to vulnerable parts of Antarctica's ice shelves in the future. Antarctic surface hydrology is in its infancy and many processes I will discuss have rarely been studied in Antarctica before. My hope with this talk is to expose the audience to these fascinating phenomena and spark discussion of how the important aspects of Antarctic surface hydrology could be incorporated into large-scale climate and ice-sheet models.