Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean
Meridional cross sections of effective diffusivity in the Southern Ocean are presented and discussed. The effective diffusivity, K[subscript eff], characterizes the rate at which mesoscale eddies stir properties on interior isopycnal surfaces and laterally at the sea surface. The distributions are o...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | en_US |
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American Meteorological Society
2010
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| Online Access: | http://hdl.handle.net/1721.1/60330 https://orcid.org/0000-0001-9230-3591 |
| _version_ | 1811082102960029696 |
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| author | Abernathey, Ryan Patrick Mazloff, Matthew R. Shuckburgh, Emily Marshall, John C |
| author2 | Joint Program in Oceanography/Applied Ocean Science and Engineering |
| author_facet | Joint Program in Oceanography/Applied Ocean Science and Engineering Abernathey, Ryan Patrick Mazloff, Matthew R. Shuckburgh, Emily Marshall, John C |
| author_sort | Abernathey, Ryan Patrick |
| collection | MIT |
| description | Meridional cross sections of effective diffusivity in the Southern Ocean are presented and discussed. The effective diffusivity, K[subscript eff], characterizes the rate at which mesoscale eddies stir properties on interior isopycnal surfaces and laterally at the sea surface. The distributions are obtained by monitoring the rate at which eddies stir an idealized tracer whose initial distribution varies monotonically across the Antarctic Circumpolar Current (ACC). In the absence of observed maps of eddying currents in the interior ocean, the advecting velocity field is taken from an eddy-permitting state estimate of the Southern Ocean (SOSE). A three-dimensional advection–diffusion equation is solved and the diffusivity diagnosed by applying the Nakamura technique on both horizontal and isopycnal surfaces. The resulting meridional sections of K[subscript eff] reveal intensified isopycnal eddy stirring (reaching values of ~2000 m[superscript 2]s[superscript −1]) in a layer deep beneath the ACC but rising toward the surface on the equatorward flank. Lower effective diffusivity values (~500 m[superscript 2]s[superscript −1]) are found near the surface where the mean flow of the ACC is strongest. It is argued that K[subscript eff] is enhanced in the vicinity of the steering level of baroclinic waves, which is deep along the axis of the ACC but shallows on the equatorial flank. Values of K[subscript eff] are also found to be spatially correlated with gradients of potential vorticity on isopycnal surfaces and are large where those gradients are weak and vice versa, as expected from simple dynamical arguments. Finally, implications of the spatial distributions of K[subscript eff] for the dynamics of the ACC and its overturning circulation are discussed. |
| first_indexed | 2024-09-23T11:57:37Z |
| format | Article |
| id | mit-1721.1/60330 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:57:37Z |
| publishDate | 2010 |
| publisher | American Meteorological Society |
| record_format | dspace |
| spelling | mit-1721.1/603302024-05-15T05:37:11Z Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean Abernathey, Ryan Patrick Mazloff, Matthew R. Shuckburgh, Emily Marshall, John C Joint Program in Oceanography/Applied Ocean Science and Engineering Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Woods Hole Oceanographic Institution Marshall, John C. Marshall, John C. Abernathey, Ryan Patrick Mazloff, Matthew R. Meridional cross sections of effective diffusivity in the Southern Ocean are presented and discussed. The effective diffusivity, K[subscript eff], characterizes the rate at which mesoscale eddies stir properties on interior isopycnal surfaces and laterally at the sea surface. The distributions are obtained by monitoring the rate at which eddies stir an idealized tracer whose initial distribution varies monotonically across the Antarctic Circumpolar Current (ACC). In the absence of observed maps of eddying currents in the interior ocean, the advecting velocity field is taken from an eddy-permitting state estimate of the Southern Ocean (SOSE). A three-dimensional advection–diffusion equation is solved and the diffusivity diagnosed by applying the Nakamura technique on both horizontal and isopycnal surfaces. The resulting meridional sections of K[subscript eff] reveal intensified isopycnal eddy stirring (reaching values of ~2000 m[superscript 2]s[superscript −1]) in a layer deep beneath the ACC but rising toward the surface on the equatorward flank. Lower effective diffusivity values (~500 m[superscript 2]s[superscript −1]) are found near the surface where the mean flow of the ACC is strongest. It is argued that K[subscript eff] is enhanced in the vicinity of the steering level of baroclinic waves, which is deep along the axis of the ACC but shallows on the equatorial flank. Values of K[subscript eff] are also found to be spatially correlated with gradients of potential vorticity on isopycnal surfaces and are large where those gradients are weak and vice versa, as expected from simple dynamical arguments. Finally, implications of the spatial distributions of K[subscript eff] for the dynamics of the ACC and its overturning circulation are discussed. National Science Foundation (U.S.). Division of Polar Programs 2010-12-20T17:28:15Z 2010-12-20T17:28:15Z 2010-01 2009-06 Article http://purl.org/eprint/type/JournalArticle 0022-3670 1520-0485 http://hdl.handle.net/1721.1/60330 Abernathey, Ryan et al. “Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean.” Journal of Physical Oceanography 40.1 (2010): 170-184. © 2010 American Meteorological Society https://orcid.org/0000-0001-9230-3591 en_US http://dx.doi.org/10.1175/2009jpo4201.1 Journal of Physical Oceanography Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Meteorological Society American Meteorological Society |
| spellingShingle | Abernathey, Ryan Patrick Mazloff, Matthew R. Shuckburgh, Emily Marshall, John C Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean |
| title | Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean |
| title_full | Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean |
| title_fullStr | Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean |
| title_full_unstemmed | Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean |
| title_short | Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean |
| title_sort | enhancement of mesoscale eddy stirring at steering levels in the southern ocean |
| url | http://hdl.handle.net/1721.1/60330 https://orcid.org/0000-0001-9230-3591 |
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