Abstract

Diapycnal mixing is a process central to the closure of the global overturning circulation, allowing dense waters created at high latitudes to return to mid-depths in the ocean. One of the aims of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) is to investigate the magnitude and distribution of diapycnal mixing in and around Drake Passage, a region of the Southern Ocean where intense rates of mixing have been observed. In this presentation I will give an account of the work I carried out during my PhD, which contributes to the aims of the DIMES project.

I will describe a number of efforts to model the evolution of a tracer in the ACC , beginning in the Southeast Pacific and progressing through Drake Passage, and compare the model outputs with results from the DIMES tracer release experiment. I will show results from a simple 2D model, and a more complex 3D model which makes use of offline MITgcm combined with velocity fields derived from satellite altimetry. Diagnosed diapycnal diffusivities will be reported, and comparisons which were made using the 3D model between diapycnal mixing rates derived from microstructure measurements, from linear lee wave theory, and from the tracer observations will be shown.