Sack Lunch Seminar (SLS)

Turbulence measurements and vertical mixing rates in the Southern Ocean


Mixing processes in the Southern Ocean are believed to have a large impact on the global overturning cycle, as nearly all deep water masses in the global ocean outcrop in the Antarctic Circumpolar region. Indirect estimates of mixing have previously been used to assess the diffusivity of buoyancy in the Southern Ocean, typically suggesting very large turbulence levels characterize the full range of depth. These estimates further suggest the Antarctic Circumpolar Current as a source for internal wave energy driving elevated turbulence levels.


A multiyear study of mixing processes in the Southern Ocean was initiated in 2009 via the injection of a manufactured tracer in the open-Pacific, upstream of Drake Passage. This study: Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES), involves the subsequent inventory of the tracer cloud as it spreads subject to the influence of the ACC system and diffusion processes. Here, we will discuss initial results concerning diapycnal-mixing rates estimated from direct measurements of turbulence levels made during expeditions in 2010 and 2011.