Research Objectives:
What is the role of the antarctic slope front (ASF) 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 understood, but the processes by which these water masses enter the deep ocean circulation are not. Our program, called AnSlope, will address 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, as well as understand the compensatory poleward flow of waters from the oceanic regime. The upper continental slope is the critical gateway for the exchange of shelf and deep ocean waters. Here the topography, velocity, and density fields associated with the nearly ubiquitous ASF must strongly influence the transfer of water properties between the shelf and oceanic regimes.
AnSlope has four specific objectives:
+ Determine the ASF's mean structure and the principal scales of spatial and temporal variability, and estimate the ASF's role in cross-slope exchanges and mixing of adjacent water masses;
+ Determine the influence of slope topography on frontal location and outflow of dense shelf water;
+ Establish the role of frontal instabilities, benthic boundary layer transports, tides, and other oscillatory processes on cross-slope advection and fluxes; and
+ Assess the effect of shear-driven and double-diffusive mixing, lateral mixing identified through intrusions, and nonlinearities in the equation of state on the rate of descent and the fate of outflowing, near-freezing shelf water.
We will address these objectives with an integrated observational and modeling program. We will perform a set of measurements whose basic elements are moorings, microstructure analysis, tracers, and basic tidal modeling. Three cruises over a 12- to 14-month period beginning in the austral summer of 2003 will provide the data. Moorings will be in place throughout this period. Existing Italian and German programs will provide enhancement and a test bed for our parameterizations of cross-front exchange.
