Abstract
AbstractIn the Amundsen Sea, warm saline Circumpolar Deep Water (CDW) crosses the continental shelf toward the vulnerable West Antarctic ice shelves, contributing to their basal melting. Due to lack of observations, little is known about the spatial and temporal variability of CDW, particularly seasonally. A new data set of 6,704 seal tag temperature and salinity profiles in the easternmost trough between February and December 2014 reveals a CDW layer on average 49 dbar thicker in late winter (August to October) than in late summer (February to April), the reverse seasonality of that seen at moorings in the western trough. This layer contains more heat in winter, but on the 27.76 kg/m3 density surface CDW is 0.32°C warmer in summer than in winter, across the northeastern Amundsen Sea, which may indicate that wintertime shoaling offshelf changes CDW properties onshelf. In Pine Island Bay these seasonal changes on density surfaces are reduced, likely by gyre circulation.
Highlights
Loss of the unstable West Antarctic ice sheet could produce sea level rise of 3.2 m [Bamber et al, 2009] if it melts completely, of which approximately 40% by volume would drain via the Pine Island Glacier and Thwaites Glacier [Payne et al, 2004]
300 db, isotherms are shallower in winter than in summer, the Circumpolar Deep Water (CDW) layer is warmer in winter than in summer on pressure surfaces (Figure 2e), and more saline
The warmest CDW of the Amundsen Sea is found in the eastern trough
Summary
Loss of the unstable West Antarctic ice sheet could produce sea level rise of 3.2 m [Bamber et al, 2009] if it melts completely, of which approximately 40% by volume would drain via the Pine Island Glacier and Thwaites Glacier [Payne et al, 2004]. Saline Circumpolar Deep Water (CDW) is implicated in this acceleration, flowing southward across the Amundsen Sea continental shelf from the open ocean and mixing with the shelf sea water masses This modified CDW ( CDW) is characterized by a subsurface temperature maximum, typically greater than 0◦C, with absolute salinities greater than 34.7 g/kg. It flows beneath the thermocline at 350 to 650 m [Jacobs et al, 2011; Dutrieux et al, 2014], penetrating the Pine Island ice shelf cavity [Jenkins et al, 1997], melting and thinning the ice shelf from below. Key questions include: how thick and how warm is the CDW layer near the continental shelf, how are the thickness and temperature of the CDW layer modified as it flows south to the Pine Island ice shelf cavity, and do the temperature and thickness vary seasonally
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