The Impact of Overturning and Horizontal Circulation in Pine Island Trough on Ice Shelf Melt in the Eastern Amundsen Sea

• Published in: Journal of physical oceanography Vol. 49; no. 1; pp. 63 - 83
• Main Authors: Webber, Benjamin G. M., Heywood, Karen J., Stevens, David P., Assmann, Karen M.
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.01.2019
• Subjects: Antarctica; Baroclinic flows; Barotropic flows; Barotropic mode; Circulation; circumpolar deep-water; Continental shelves; continental-shelf; Decadal variability; Deep water; Ecology; Ekman pumping; Ekologi; embayment; Freshwater; glacial meltwater; Heat; Ice shelves; inflow; Inland water environment; Land ice; Melting; Meridional overturning circulation; Ocean circulation; Ocean currents; Ocean models; Oceanography; Oceans; Sea level; Seawater; sensitivity; Shelf dynamics; Shelf edge; Simulation; Suction; Time series; Transport; Variability; Velocity; Water circulation; Water mass transformation; Water masses; Pine Island; Amundsen Sea; Antarctica
• ISSN: 0022-3670; 1520-0485
• DOI: 10.1175/JPO-D-17-0213.1

Abstract The ice shelves around the Amundsen Sea are rapidly melting as a result of the circulation of relatively warm ocean water into their cavities. However, little is known about the processes that determine the variability of this circulation. Here we use an ocean circulation model to diagnose the relative importance of horizontal and vertical (overturning) circulation within Pine Island Trough, leading to Pine Island and Thwaites ice shelves. We show that melt rates and southward Circumpolar Deep Water (CDW) transports covary over large parts of the continental shelf at interannual to decadal time scales. The dominant external forcing mechanism for this variability is Ekman pumping and suction on the continental shelf and at the shelf break, in agreement with previous studies. At the continental shelf break, the southward transport of CDW and heat is predominantly barotropic. Farther south within Pine Island Trough, northward and southward barotropic heat transports largely cancel, and the majority of the net southward temperature transport is facilitated by baroclinic and overturning circulations. The overturning circulation is related to water mass transformation and buoyancy gain on the shelf that is primarily facilitated by freshwater input from basal melting.