Formation and export of dense shelf water from the Adelie Depression, East Antarctica

• Published in: Journal of Geophysical Research
• Main Authors: Williams, GD, Bindoff, NL, Marsland, SJ, Rintoul, SR
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2008
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Adelie Depression; Antarctic; Australian Antarctic Basin; Australian-Antarctic Basin; East Antarctica; Antarc*; Antarctica; Antarctica Journal; Ice Shelf
• Online Access: https://doi.org/10.1029/2007JC004346; http://ecite.utas.edu.au/55433

Coastal polynyas in the Adelie Depression are an important source of AntarcticBottom Water to the Australian-Antarctic Basin. We present time series (April 1998 toMay 1999 and August 1999 to February 2000) of data from temperature-salinitysensors, in both the Adelie Depression and the known outflow region of the AdelieSill, to describe the annual cycle of shelf water densities. From April throughSeptember, salinification beneath the polynya produces dense shelf waters. DuringSeptemberOctober, shelf water densities in the depression peak at 27.94 kg m 3,and the cooling and freshening signature of Ice Shelf Water is observed north ofBuchanan Bay. In NovemberDecember, shelf water densities decrease as intrusions ofwarm and relatively fresh modified Circumpolar Deep Water enter east of the AdelieSill. From JanuaryMarch the surface layer is conditioned by the cooling of theatmosphere, which overturns the upper water column. At the Adelie Sill, observeddaily mean currents were approximately 10 cm s 1 with intense instantaneous currentsgreater than 50 cm s 1 at the sill depth. Using an idealized outflow region with arectangular cross-sectional area (6 106 m2), we present the first estimates of shelfwater export by potential density class. Assuming shelf water with a minimum densityof 27.88 kg m 3 has sufficient negative buoyancy for downslope mixing and afourfold volume increase (1:3 mixing ratio) from entrainment, the dense shelf water exportof 0.10.5 Sv results in an annual average production of bottom water in this region ofbetween 0.4 and 2.0 Sv. The wide range in bottom water estimate results from datalimitations, and a narrowing of this range requires further mooring observations.