Mechanisms of Deep and Bottom Water Ventilation over the Antarctic Continental Slope

Аннотация

Actual in situ observations at the Antarctic continental slope performed with eddy-resolving spatial resolution were used. As a result, some parameterizations were verified that describe the processes of instability of density flows on a sloping bottom derived during the laboratory experiments. These processes were identified based on observational data. Any changes in the bottom slope (local or general, linked to the transition of the steep slope into the deep-sea floor) lead to changes in the regime of dense water runoff. The resulting hydraulic jumps lead to the turbulent mixing and function as one of the main mechanisms of ventilation of deep and bottom water. In the areas of local bottom rubs, disturbances like leeward waves are sometimes observed at the dense water top. They cause the intrusive layering and subsequent occurrence of turbulence centers in the slope area; the eddy lenses which also take part in the slope water ventilation are sometimes observed over bottom rubs. A strong baroclinity of the Antarctic slope front (ASF) in a steep part of the slope is another mechanism of deep water ventilation. It leads to the instability of cascading, subsequent intrusive layering and eddy formation. The baroclinic instability is amplified by the increased dynamics of dense water runoff at the bottom slope increase. However, the realization of shear instability at density interface is possible but at the smaller spatial scale than the instability scales observed in the ASF area.