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Circulation and melting beneath George VI Ice Shelf, Antarctica

Jenkins, Adrian; Jacobs, Stan. 2008 Circulation and melting beneath George VI Ice Shelf, Antarctica. Journal of Geophysical Research, 113 (C4), C04013. 10.1029/2007JC004449

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Abstract/Summary

Oceanographic data are presented from the eastern Bellingshausen Sea, representing the first near-contemporaneous sampling of conditions near both the northern and southern ice fronts of George VI Ice Shelf. Circumpolar Deep Water (CDW) with a temperature in excess of 1 degrees C floods the entire continental shelf and forms the main inflow to the cavity beneath the ice shelf. We use measurements of salinity, potential temperature, stable isotope ratios and dissolved oxygen, helium, and neon to show that the outflows contain meltwater in concentrations that rise to a maximum of around 3%. Assuming that the currents are in geostrophic balance, we calculate relative velocities along the ice front sections, then estimate the absolute velocity by inversion of the tracer conservation equations. We obtain an overall mean melt rate of 3-5 m a(-1) and a net south-to-north throughflow beneath the ice shelf of 0.17-0.27 Sv. The mean melt rate exceeds that required for equilibrium, consistent with recent observations of ice shelf thinning and retreat. Melting beneath the ice shelf drives upwelling of about 0.1 Sv in total of CDW into the surface mixed layer at the two ice fronts. The effective vertical heat flux per unit area of ice shelf cover is 8 W m(-2), more than 4 times that estimated for vertical diffusion through the main pycnocline of the neighboring open water region. The south-to-north throughflow carries a particularly strong signature of upwelled CDW, including low dissolved oxygen and high nutrient concentrations, north into Marguerite Bay.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1029/2007JC004449
Programmes: BAS Programmes > Global Science in the Antarctic Context (2005-2009) > Antarctic Climate and the Earth System
ISSN: 0148-0227
NORA Subject Terms: Marine Sciences
Glaciology
Date made live: 17 Jan 2011 11:47
URI: http://nora.nerc.ac.uk/id/eprint/11529

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