FRAM STRAIT: A VITAL LINK IN THE LARGE-SCALE OCEAN CIRCULATION

Knut Aagaard (UW), Andrew Roach, Richard Moritz (UW), Jens Meincke (University
of Hamburg)

Corresponding author: Knut Aagaard (aagaard@apl.washington.edu)

OVERVIEW

The export of freshwater through Fram Strait in the form of sea ice has been hypothesized to influence the global ocean overturning circulation.  To address the variability of this freshwater discharge, we collected six years of ice thickness observations over the continental slope at 79° N in Fram Strait.  During a number of these years the annual cycle of ice thickness was out of phase with the thermodynamic forcing, since the maximum observed ice thickness occurred in summer and the minimum in winter.  Using these observations, we scale the mean thickness equation for sea ice, finding that the ice thickness in Fram Strait depends on the shifting balance among the first-order effects of thermodynamics, advection, and divergence.  The divergence is computed as the residual in this procedure, yielding a mean value of about 10-8 s-1, in agreement with the estimate of Kwok and Rothrock [1999].  We suggest that the variability of the southward ice flux is smaller than has been thought, perhaps one-half as large, but that the amplitude and phase of the annual cycle, which appears to be controlled locally, is critical to the actual volume transport.
 
 

REFEREED PUBLICATIONS (back)

Aagaard, K., C. Darnall, and P. Greisman, Year-long current measurements
  in the Greenland-Spitsbergen Passage, Deep Sea Res., 20, 743-746, 1973.

Aagaard, K., and P. Greisman, Toward new mass and heat budgets for the
  Arctic Ocean, J. Geophys. Res., 80, 3821-3827, 1975.

Aagaard, K., Inflow from the Atlantic to the Polar Basin, in The Arctic
  Ocean: The Hydrographic Environment and the Fate of Pollutants, edited
  by L. Rey, pp. 69-81, Macmillan, London, 1982.

Aagaard, K., A. Foldvik, and S.R. Hillman, The West Spitsbergen Current:
  Structure and disposition, J. Geophys. Res., 92, 3778-3784, 1987.

Foldvik, A., K. Aagaard, and T. Tørresen, On the velocity field of the East
  Greenland Current, Deep Sea Res., 35, 1335-1354, 1988.

Aagaard, K., E. Fahrbach, J. Meincke, and J.H. Swift, Saline outflow from
  the Arctic Ocean: Its contribution to the deep waters of the Greenland,
  Norwegian, and Iceland seas. J. Geophys. Res., 96, 20433-20441, 1991.

Jonsson, S., A. Foldvik, and K. Aagaard, The structure and atmospheric
  forcing of the mesoscale velocity field in Fram Strait, J. Geophys. Res.,
  97, 12585-12600, 1992.

Woodgate, R.A., U. Schauer and E. Fahrbach, 'Moored Current Meters in
  the Fram Strait at 79N: Preliminary Results with special emphasis on the
  West Spitsbergen Current.', Berichte aus dem Fachbereich Physik,
  AWI, No.91, 150pp.

We gratefully acknowledge financial support for this work from the National Oceanic and Atmospheric Administration (NOAA).
 

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