Research Objectives:
The AnSlope project seeks to better understand 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. AnSlope objectives include determination of the mean ASF structure, its principal scales of variability and instability, its role in diapycnal and lateral mixing of adjacent water masses, and the function of benthic boundary layer transports, tides and other oscillatory processes.
The 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.
AnSlope cruise III (NBP04-08) is the last and 'late winter' component of the project. Researchers plan to occupy as many CTD/LADCP (Conductivity Temperature Depth/Lowered Acoustic Doppler Current Profiler) stations as possible across and along the ASF in the Ross Sea, including a transect near previously deployed bottom-moored arrays of current, temperature, conductivity and pressure sensors. Synergistic projects will sample for geochemical tracers, nutrients and oxygen isotopes, make casts to measure ocean microstructure, investigate surface water properties during transects to and from New Zealand, and survey the near-surface environment, including elements of its ecosystem and sea ice field.
