2002-2003 Science Planning Summary

Oceans & Climate

Dr. Bernhard Lettau
Program Manager


NSF/OPP 01-25172
Station: RV/IB Nathaniel B Palmer
RPSC POC: Karl Newyear
Research Site(s): RV/IB NBP

ANSLOPE: Cross slope exchanges at the Antarctic slope front
Dr. Arnold L. Gordon
Columbia University
Lamont-Doherty Earth Observatory

Deploying Team Members: Karen Assman . Andrea Bergamasco . Kenneth Boda . Amy Bratcher . Kathryn Brooksforce . Enrique Curchitser . Arnold Gordon . Bruce Huber . Stanley S Jacobs . Philip A Mele . Alejandro H Orsi . Laurence Padman . John Simpkins . Qian Song . Basil Stanton . Enrico Zambianchi
Research Objectives: The AnSlope project seeks to determine the role of the Antarctic Slope Front (ASF) and continental slope morphology in the exchanges of mass, heat, and freshwater between the continental shelf and oceanic regimes, in particular those leading to outflows of dense water into intermediate and deep layers of the adjacent deep basins and world ocean circulation.

AnSlope has four specific objectives: (1) Determine the ASF mean structure and the principal scales of variability, and estimate the role of the front in cross-slope exchanges and mixing of adjacent water masses, (2) Determine the influence of slope topography 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, lateral mixing identified through intrusions, and nonliearities in the equation of state on the rate of descent and fate of outflowing, near-freezing shelf water.

Three AnSlope science cruises will deploy on the Research Vessel/Icebreaker Nathaniel B. Palmer. The objectives for the first cruise, NBP 03-02 are to:

- Conduct a rapid survey of the ASF in the northwest Ross Sea using T7 and T5 XBT's (expendable bathythermographs

- Obtain high resolution swath bathymetry via multibeam in the ASF region,

- Deploy, recover and redeploy nine instrumented moorings in a concentrated array at a site to be selected upon completion of the above surveys, and

- To conduct approximately 120 CTD (conductivity, temperature, depth) casts with LADCP, microstructure sensors, and tracer chemistry at specific stations along and across the ASF region.

Field Season Overview:
Researchers on this R/V Nathaniel B. Palmer cruise will conduct a rapid survey of the Antarctic Slope Front (ASF) in the northwest Ross Sea using eXpendable BathyThermographs (XBTs), Acoustic Doppler Current Profiler (ADCP), and multibeam sonar. The survey will be followed by the deployment of nine ocean-bottom moorings.

A series of Conductivity-Temperature-Depth (CTD) and researcher-provided Lowered Acoustic Doppler Current Profiler (LADCP) casts will be conducted at 10-kilometer increments along the ASF from the mooring array to the Italian CLIMA program site east of the array. This will be followed by a series of CTD/LADCP casts near the mooring array every 5 to 10 kilometers.

At the end of the cruise, all moorings and their will be recovered. The moorings and instruments will then be serviced and redeployed.