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AGU: Geophysical Research Letters

 

Keywords

  • Antarctic watermasses
  • Ice shelf basal melting
  • Ice-ocean interaction
  • Polar oceanography

Index Terms

  • 0728 - Ice shelves
  • 4207 - Arctic and Antarctic oceanography
  • 4217 - Coastal processes
  • 4219 - Continental shelf and slope processes
  • 4283 - Water masses

Paper in Press

GEOPHYSICAL RESEARCH LETTERS, doi:10.1029/2012GL051012

Two years of oceanic observations below the Fimbul Ice Shelf, Antarctica

Key Points
  • We present two years of unique observations below the Fimbul Ice Shelf
  • Cold water below the ice suggests low basal melting
  • Solar heated surface water and warm pulses at depth provide heat for melting

Authors:

Tore Hattermann

Ole A. Nøst

Jonathan M. Lilly

Lars Henrik Smedsrud

The mechanisms by which heat is delivered to Antarctic ice shelves are a major source of uncertainty when assessing the response of the Antarctic ice sheet to climate change. Direct observations of the ice shelf-ocean interaction are extremely scarce, and present ice shelf-ocean models struggle to predict reason able melt rates. Our two years of data during 2010-2012 from three oceanic moorings below the Fimbul Ice Shelf in the eastern Weddell Sea show cold cavity waters, with average temperatures of less than 0.1 {degree sign}C above the surface freezing point. This suggests rather low basal melt rates, consistent with remote sensing based, steady state mass balance estimates in this sector of the Antarctic coast. Oceanic heat for basal melting is found to be sup-plied by two sources of warm water that enter below the ice: (i) eddy-like bursts of Modified Warm Deep Water accesses the cavity at depth during eight months of the record; and (ii) a seasonal inflow of warm, fresh surface water flushes parts of the ice base with temperatures above freezing, during late summer and fall. This interplay of processes implies that basal melting cannot simply be parameterized by coastal deep ocean temperatures, but is directly linked to both solar forcing at the surface as well as to coastal processes controlling deep ocean heat fluxes.

Received 27 March 2012; accepted 25 May 2012.

Citation: Hattermann, T., O. A. Nøst, J. M. Lilly, and L. H. Smedsrud (2012), Two years of oceanic observations below the Fimbul Ice Shelf, Antarctica, Geophys. Res. Lett., doi:10.1029/2012GL051012, in press.