Exchange across the shelf break at high southern latitudes Center for Coastal Physical Oceanography, Old Dominion University, Norfolk, Virginia, USA
Received: 22 Dec 2009 – Published in Ocean Sci. Discuss.: 26 Jan 2010 Abstract. Exchange of water across the Antarctic shelf break has considerable
scientific and societal
importance due to its effects on circulation and biology of the region,
conversion of water masses as part of the global overturning circulation and
basal melt of glacial ice and the consequent effect on sea level rise. The
focus in this paper is the onshore transport of warm, oceanic Circumpolar
Deep Water (CDW); export of dense water from these shelves is equally important,
but has been the focus of other recent papers and will not be considered here.
A variety of physical mechanisms are described which could play a role in
this onshore flux. The relative importance of some processes are evaluated
calculations. A numerical model for the Ross Sea continental shelf is used
as an example of a more comprehensive evaluation of the details of
cross-shelf break exchange. In order for an
ocean circulation model to simulate these processes
at high southern latitudes, it needs to have high spatial resolution,
realistic geometry and bathymetry. Grid spacing smaller than the first
baroclinic radius of deformation (a few km) is required to adequately represent
the circulation. Because of flow-topography interactions, bathymetry needs
to be represented at these same small scales.
Atmospheric conditions used to force these circulation models also need to be
known at a similar small spatial resolution (a few km) in order to represent
orographically controlled winds (coastal jets) and katabatic winds.
variability of surface winds strongly influences the structure of the mixed
layer. Daily, if not more frequent, surface fluxes must be imposed for
a realistic surface mixed layer.
Sea ice and ice shelves are important components of the coastal
circulation. Ice isolates the ocean from exchange with the atmosphere,
especially in the winter. Melting and freezing of both sea ice and glacial
ice influence salinity and thereby the character of shelf water.
These water mass conversions are known to have an important
effect on export of dense water from many Antarctic coastal areas.
An artificial dye, as well as temperature, is used to diagnose the flux of
CDW onto the shelf. Model results for the Ross Sea show a vigorous
onshore flux of oceanic water across the shelf break both at depth and at
the surface as well as creation of dense water (High Salinity Shelf Water)
created by coastal polynyas in the western Ross Sea.
Revised: 06 May 2010 – Accepted: 14 May 2010 – Published: 28 May 2010
Citation: Klinck, J. M. and Dinniman, M. S.: Exchange across the shelf break at high southern latitudes, Ocean Sci., 6, 513-524, doi:10.5194/os-6-513-2010, 2010.