Dynamic Thinning and Grounding Line Retreat in Porpoise Bay, Wilkes Land, East Antarctica

Abstract. The East Antarctic Ice Sheet (EAIS) is often considered less vulnerable to climate change than the West Antarctic or Greenland ice sheets, but some regions of the EAIS have been losing mass over recent decades. In particular, mass loss in Wilkes Land, which overlies the Aurora Subglacial Basin, is thought to have accelerated over the past two decades. However, whilst several large outlet glaciers drain this region, few have been studied in detail. Here, we present new data on the recent ice dynamics of four outlet glaciers that drain into Porpoise Bay, Wilkes Land, which includes Holmes East, Holmes West, and Frost glaciers. We use optical satellite imagery, differential synthetic aperture radar interferometry, and a range of previously published datasets to describe changes in the ice-shelf front, grounding line position, ice surface velocity and ice surface elevation over the last three decades. Our results reveal evidence of dynamic changes in the region, characterised by thinning of grounded ice and grounding line retreat, albeit with large uncertainties. We find an indication of Circumpolar Deep Water proximal to the continental shelf break that could access the glaciers through deep cross-shelf troughs, which is consistent with previous estimates of high rates of basal melting beneath their floating tongues/ice shelves. Our results also support previous observations of near-synchronous ice-shelf calving across Porpoise Bay's ice shelves, following the break-out of multi-year sea ice, and find an additional recent calving event, further highlighting the vulnerability of this region to ongoing and future changes in ocean and sea-ice conditions.