Warm Modified Circumpolar Deep Water Intrusions Drive Ice Shelf Melt and Inhibit Dense Shelf Water Formation in Vincennes Bay, East Antarctica

Abstract

AbstractAntarctic Bottom Water (AABW) production supplies the deep limb of the global overturning circulation and ventilates the deep ocean. While the Weddell and Ross Seas are recognized as key sites for AABW production, additional sources have been discovered in coastal polynya regions around East Antarctica, most recently at Vincennes Bay. Vincennes Bay, despite encompassing two distinct polynya regions, is considered the weakest source, producing Dense Shelf Water (DSW) only just dense enough to contribute to the lighter density classes of AABW found offshore. Here we provide the first detailed oceanographic observations of the continental shelf in Vincennes Bay (104‐111°E), using CTD data from instrumented elephant seals spanning from February to November of 2012. We find that Vincennes Bay has East Antarctica’s warmest recorded intrusions of modified Circumpolar Deep Water (mCDW) and that warm mCDW drives basal melt under Vanderford and Underwood ice shelves. Our study also provides the first direct observational evidence for the inflow of meltwater to this region, which increases stratification and hinders DSW formation, and thus AABW production. The Vincennes Bay glaciers, together with the Totten Glacier, drain part of the Aurora Basin, which holds up to 7 m of sea level rise equivalent. Our results highlight the vulnerability of the East Antarctic Ice Sheet to intrusions of mCDW.