AnSlope: Cross-slope exchanges at the Antarctic Slope Front

Alejandro H. Orsi
Phone: (979) 845-4014
Fax: (979) 847-8879
Thomas Whitworth III
Phone: (979) 845-5872
Fax: (979) 847-8879

AnSlope was an oceanographic experiment carried out during 2003-2005 in the Ross Sea, Antarctica, in collaboration with Arnold L. Gordon, Stan Jacobs, Martin Visbeck, William Smethie and Peter Schlosser of the Lamont-Doherty Earth Observatory (LDEO); Laurence Padman and Robin Muench of the Earth and Space Research (ESR); and Dale Pillsbury of Oregon State University (OSU). Further information about this program can be found in the related AnSlope sites at LDEO, ESR, and OSU.

The influence of cold Antarctic waters originating in to the global ocean circulation and climate is now well understood, but the processes by which these water masses enter the deep ocean circulation are not. AnSlope addresses this problem. We identify the upper continental slope as the critical gateway for the exchange of shelf and deep ocean waters. Here the topography, velocity and density fields associated with the nearly ubiquitous Antarctic Slope Front (ASF) must strongly influence the advective and turbulent transfer of water properties between the shelf and oceanic regimes.


To identify and characterize the principal physical processes that govern the transfer of shelf-modified dense water into intermediate and deep layers of the adjacent deep ocean, and the compensatory poleward flow of waters from the oceanic regime.


  1. Determine the ASF mean structure and the principal scales of variability (spatial from ~1 km to ~100 km, and temporal from tidal to seasonal), and estimate the role of the Front on cross-slope exchanges and mixing of adjacent water masses;
  2. Determine the influence of slope topography (canyons, proximity to a continental boundary, isobath divergence/convergence) on frontal location and outflow of dense Shelf Water;
  3. Establish the role of frontal instabilities, benthic boundary layer transports, tides and other oscillatory processes on cross-slope advection and fluxes; and
  4. Assess the effect of diapycnal mixing (shear-driven and double-diffusive), lateral mixing identified through intrusions, and nonlinearities in the equation of state (thermobaricity and cabbeling) on the rate of descent and fate of outflowing, near-freezing Shelf Water.

Field Program

Acquisition of measurements is focused over the outer continental shelf and the upper slope of the northwestern Ross Sea. Field work includes three oceanographic cruises on the N.B. Palmer icebreaker. During the first two cruises we deployed and recovered instruments that measured time series of currents and T-S-P series for a year. A third AnSlope cruise will take place in October-November of 2004. A second year of records will be recovered on the Palmer in January-February 2005. An integrated basic modeling program will also be undertaken to study tides, plume dynamics, and frontal dynamics.

Broad summary of the various AnSlope components and principal investigators:


AnSlope is funded by the National Science Foundation, Office of Polar Programs. It is the 4th in a series of projects under the SCOR-affiliated International Antarctic Zone (iAnZone) program.

Deployment Cruise: February-April 2003



Recovery Cruise: February-April 2004