Warm Modified Circumpolar Deep Water Intrusions Drive Ice Shelf Melt and Inhibit Dense Shelf Water Formation in Vincennes Bay, East Antarctica. Issue 8 (30th July 2021)

• Record Type: Journal Article
• Authors: Ribeiro, N.; Herraiz‐Borreguero, L.; Rintoul, S. R.; McMahon, C. R.; Hindell, M.; Harcourt, R.; Williams, G.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-30
• Subjects: mCDW intrusions -- basal melt -- AABW -- seal CTD -- Antarctic Margins -- Antarctic Coastal Circulation; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2020JC016998
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Antarctic 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. Plain Language Summary: The production of Antarctic Bottom Water (AABW), the densest water in the ocean, is a key factor of the global ocean circulation, distributing heat and helping to regulate the climate. The formation of AABW is dependent on the formation of Dense Shelf Water (DSW) in coastal regions called polynyas. In polynyas, including those of Vincennes Bay, seawater loses heat to the atmosphere while gaining salt through sea‐ice formation. The study shows that relatively warm water that is normally offshore is coming onto the continental shelf in Vincennes Bay and melting the local ice shelves. The input of glacial meltwater then increases the stratification of the water column, making it harder for polynyas to establish top‐to‐bottom convection and to form DSW. In addition, warm waters accessing ice shelf cavities at depth could be particularly threatening to the glaciers as they are responsible for the highest observed ice shelf basal melting. Key Points: Oceanographic profiles collected by seals are used to determine the circulation and seasonal cycle in Vincennes Bay Modified Circumpolar Deep Water is widespread and drives basal‐melt of local glaciers Dense Shelf Water formation may be susceptible to changes in input of glacial melt‐water