Diapycnal mixing in the Antarctic Circumpolar Current
Ledwell, James R.
St. Laurent, Louis C.
Girton, James B.
Toole, John M.
MetadataShow full item record
KeywordDiapycnal mixing; Currents; Antarctica; Ocean circulation; Meridional overturning circulation
The vertical dispersion of a tracer released on a density surface near 1500-m depth in the Antarctic Circumpolar Current west of Drake Passage indicates that the diapycnal diffusivity, averaged over 1 yr and over tens of thousands of square kilometers, is (1.3 ± 0.2) × 10−5 m2 s−1. Diapycnal diffusivity estimated from turbulent kinetic energy dissipation measurements about the area occupied by the tracer in austral summer 2010 was somewhat less, but still within a factor of 2, at (0.75 ± 0.07) × 10−5 m2 s−1. Turbulent diapycnal mixing of this intensity is characteristic of the midlatitude ocean interior, where the energy for mixing is believed to derive from internal wave breaking. Indeed, despite the frequent and intense atmospheric forcing experienced by the Southern Ocean, the amplitude of finescale velocity shear sampled about the tracer was similar to background amplitudes in the midlatitude ocean, with levels elevated to only 20%–50% above the Garrett–Munk reference spectrum. These results add to a long line of evidence that diapycnal mixing in the interior middepth ocean is weak and is likely too small to dictate the middepth meridional overturning circulation of the ocean.
Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 241-246, doi:10.1175/2010JPO4557.1.
Showing items related by title, author, creator and subject.
Benthuysen, Jessica A.; Thomas, Leif N.; Lentz, Steven J. (American Meteorological Society, 2015-01)Model analyses of an alongshelf flow over a continental shelf and slope reveal upwelling near the shelf break. A stratified, initially uniform, alongshelf flow undergoes a rapid adjustment with notable differences onshore ...
Meyer, Amelie; Sloyan, Bernadette M.; Polzin, Kurt L.; Phillips, Helen E.; Bindoff, Nathaniel L. (American Meteorological Society, 2015-04)A key remaining challenge in oceanography is the understanding and parameterization of small-scale mixing. Evidence suggests that topographic features play a significant role in enhancing mixing in the Southern Ocean. This ...
Wang, Tao; Geyer, W. Rockwell; Engel, Patricia A.; Jiang, Wensheng; Feng, Shizuo (American Meteorological Society, 2015-11)Tidal oscillatory salt transport, induced by the correlation between tidal variations in salinity and velocity, is an important term for the subtidal salt balance under the commonly used Eulerian method of salt transport ...