Mixing variability in the Southern Ocean
Sloyan, Bernadette M.
Polzin, Kurt L.
Phillips, Helen E.
Bindoff, Nathaniel L.
MetadataShow full item record
KeywordGeographic location/entity; Southern Ocean; Circulation/ Dynamics; Diapycnal mixing; Fronts; Ocean circulation; Topographic effects; Atm/Ocean Structure/ Phenomena; Mixing
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 study uses 914 high-resolution hydrographic profiles from novel EM-APEX profiling floats to investigate turbulent mixing north of the Kerguelen Plateau, a major topographic feature in the Southern Ocean. A shear–strain finescale parameterization is applied to estimate diapycnal diffusivity in the upper 1600 m of the ocean. The indirect estimates of mixing match direct microstructure profiler observations made simultaneously. It is found that mixing intensities have strong spatial and temporal variability, ranging from O(10−6) to O(10−3) m2 s−1. This study identifies topographic roughness, current speed, and wind speed as the main factors controlling mixing intensity. Additionally, the authors find strong regional variability in mixing dynamics and enhanced mixing in the Antarctic Circumpolar Current frontal region. This enhanced mixing is attributed to dissipating internal waves generated by the interaction of the Antarctic Circumpolar Current and the topography of the Kerguelen Plateau. Extending the mixing observations from the Kerguelen region to the entire Southern Ocean, this study infers a large water mass transformation rate of 17 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) across the boundary of Antarctic Intermediate Water and Upper Circumpolar Deep Water in the Antarctic Circumpolar Current. This work suggests that the contribution of mixing to the Southern Ocean overturning circulation budget is particularly significant in fronts.
Author Posting. © American Meteorological Society, 2015. 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 45 (2015): 966–987, doi:10.1175/JPO-D-14-0110.1.
Suggested CitationArticle: Meyer, Amelie, Sloyan, Bernadette M., Polzin, Kurt L., Phillips, Helen E., Bindoff, Nathaniel L., "Mixing variability in the Southern Ocean", Journal of Physical Oceanography 45 (2015): 966–987, DOI:10.1175/JPO-D-14-0110.1, https://hdl.handle.net/1912/7289
Showing items related by title, author, creator and subject.
Connection between the decadal variability in the Southern Ocean circulation and the Southern Annular Mode Yang, Xiao-Yi; Wang, Dong Xiao; Wang, Jia; Huang, Rui Xin (American Geophysical Union, 2007-08-22)Previous studies demonstrated the remarkable upward trend of the Southern Annular Mode (SAM) and Southern Ocean wind stress in association with anthropogenic forcing. An oceanic reanalysis data set is used to investigate ...
Diapycnal mixing in the Southern Ocean diagnosed using the DIMES tracer and realistic velocity fields Mackay, Neill; Ledwell, James R.; Messias, Marie-Jose; Naveira Garabato, Alberto C.; Brearley, J. Alexander; Meijers, Andrew J. S.; Jones, Daniel C.; Watson, Andrew J. (John Wiley & Sons, 2018-04-13)In this work, we use realistic isopycnal velocities with a 3-D eddy diffusivity to advect and diffuse a tracer in the Antarctic Circumpolar Current, beginning in the Southeast Pacific and progressing through Drake Passage. ...
Yang, Xiao-Yi; Huang, Rui Xin; Wang, Dong Xiao (American Meteorological Society, 2007-07-15)Using 40-yr ECMWF Re-Analysis (ERA-40) data and in situ observations, the positive trend of Southern Ocean surface wind stress during two recent decades is detected, and its close linkage with spring Antarctic ozone depletion ...