A VITAL LINK IN THE LARGE-SCALE OCEAN CIRCULATION
Aagaard (UW), Andrew Roach, Richard Moritz (UW), Jens Meincke (University
author: Knut Aagaard (firstname.lastname@example.org)
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 . 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.
Aagaard, K., C. Darnall, and P. Greisman, Year-long
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,
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,
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,
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).
Back to High Latitude