Effects of wind and sea ice drift on the seasonal variation of warm circumpolar deep water in the Amundsen Sea

Abstract

Spatial and temporal variation of the layer of circumpolar deep water (CDW) at the center of the Amundsen Shelf was measured during two oceanographic surveys and a two-year mooring deployment. A hydrographic transect from the deep ocean into the Dotson Trough shows a local elevation of the warm deep water layer at the shelf break. On the shelf, the water flows south-east along the trough. Along its pathway to the ice shelves, CDW becomes colder and fresher, presumably because of mixing with surface water and/or glacial meltwater. The thickness of the warm layer displays seasonal variation with maximum thickness in austral summer and minimum thickness in austral winter. The Ekman pumping at the shelf break shows a strong seasonal variation coinciding with the mooring data. From February to April, a marginal ice zone close to the shelf break gives rise to a positive Ekman pumping.o the Dotson Trough shows a local elevation of the warm deep water layer at the shelf break. On the shelf, the water flows south-east along the trough. Along its pathway to the ice shelves, CDW becomes colder and fresher, presumably because of mixing with surface water and/or glacial meltwater. The thickness of the warm layer displays seasonal variation with maximum thickness in austral summer and minimum thickness in austral winter. The Ekman pumping at the shelf break shows a strong seasonal variation coinciding with the mooring data. From February to April, a marginal ice zone close to the shelf break gives rise to a positive Ekman pumping.