AnSlope

Cross-Slope Exchanges at the Antarctic Slope Front


Laurence Padman
Phone: +1 (541) 753-6695
Fax: +1 (541) 753-1999

 

Robin D. Muench
Phone: +1 (206) 726-0501
Fax: +1 (206) 726-0524

This page summarizes the AnSlope program. Further information on AnSlope can be found at the LDEO AnSlope Home Page.

ESR's specific contributions to AnSlope are described at the ESR Contributions page.

Goals and Objectives

AnSlope is a multi-institution experiment seeking to answer the question:

What is the role of the Antarctic Slope Front and continental slope morphology in the exchanges of mass, heat, and freshwater between the 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?

The importance to the global ocean circulation and climate of cold water masses originating in the Antarctic is now understood, but the processes by which these water masses enter the deep ocean circulation are not. AnSlope addresses this problem. Our primary goal is to identify the principal physical processes that govern the transfer of shelf-modified dense water into intermediate and deep layers of the adjacent deep ocean. At the same time, we seek to understand the compensatory poleward flow of waters from the oceanic regime. 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.

AnSlope has four specific objectives:

  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.

Approach

AnSlope addresses these objectives with an integrated observational and modeling program. Acquisition of a set of measurements focused over the outer continental shelf and upper slope of the northwestern Ross Sea began with a cruise on the icebreaker N. B. Palmer in February-April 2003. Field work will continue with a second cruise in early 2004, and a final cruise in late 2004. The core elements of the field work are:

In addition, basic modeling studies will be undertaken to study tides, plume dynamics, and frontal dynamics.

The various components of AnSlope studies overlap in many ways. However, a broad summary of the main foci of the principal investigators is as follows:

Acknowledgements

AnSlope is funded by the National Science Foundation, Office of Polar Programs. We gratefully acknowledge Dr. Bernhard Lettau's faith in our ability to carry out this complex experiment in a difficult environment.

AnSlope is the 4th in a series of projects under the SCOR-affiliated International Antarctic Zone (iAnZone) program.