Some Implications of Ekman Layer Dynamics for Cross-Shelf Exchange in the Amundsen Sea

• Published in: Journal of physical oceanography Vol. 42; no. 9; pp. 1461 - 1474
• Main Authors: WAHLIN, A. K, MUENCH, R. D, ARNEBORG, L, BJÖRK, G, HA, H. K, LEE, S. H, ALSEN, H
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.09.2012
• Subjects: Basins; Earth, ocean, space; Exact sciences and technology; External geophysics; Global warming; Grants; Marine; Melting; Physics of the oceans; Sea level; Antarctic Ocean; Amundsen Sea; polar regions; West Antarctica; Antarctica; Antarctic ice sheet; Bellingshausen Sea; Ross Sea; PSW, Antarctica, West Antarctica; PSW, Amundsen Sea; Antarctica, West Antarctica, West Antarctic Ice Sheet; sea water; continental shelf; interfaces; water supply; melting; Deep water; Slope current; buoyancy; Ekman layer; bottom water; shelf-slope break; warming; Polar region
• ISSN: 0022-3670; 1520-0485
• DOI: 10.1175/jpo-d-11-041.1

Abstract The exchange of warm, salty seawater across the continental shelves off West Antarctica leads to subsurface glacial melting at the interface between the ocean and the West Antarctic Ice Sheet. One mechanism that contributes to the cross-shelf transport is Ekman transport induced by along-slope currents over the slope and shelf break. An investigation of this process is applied to the Amundsen Sea shelfbreak region, using recently acquired and historical field data to guide the analyses. Along-slope currents were observed at transects across the eastern and western reaches of the Amundsen slope. Currents in the east flowed eastward, and currents farther west flowed westward. Under the eastward-flowing currents, hydrographic isolines sloped upward paralleling the seabed. In this layer, declining buoyancy forces rather than friction were bringing the velocity to zero at the seabed. The basin water in the eastern part of the shelf was dominated by water originating from 800–1000-m depth off shelf, suggesting that transport of such water across the shelf frequently occurs. The authors show that arrested Ekman layers mechanism can supply deep water to the shelf break in the eastern section, where it has access to the shelf. Because no unmodified off-shelf water was found on the shelf in the western part, bottom layer Ekman transport does not appear a likely mechanism for delivery of warm deep water to the western shelf area. Warming of the warm bottom water was most pronounced on the western shelf, where the deep-water temperature increased by 0.6°C during the past decade.