The influence of crosswind tidal currents on Langmuir circulation in a shallow ocean
Plueddemann, Albert J.
Trowbridge, John H.
Sullivan, Peter P.
MetadataShow full item record
Langmuir circulation (LC) is a turbulent process driven by wind and surface waves that plays a key role in transferring momentum, heat, and mass in the oceanic surface layer. On the coastal shelves the largest-scale LC span the whole water column and thus couple the surface and bottom boundary layers and enhance turbulent mixing. Observations and large eddy simulations (LES) of a shallow coastal ocean demonstrate that these relatively large scale Langmuir cells are strongly influenced by crosswind tidal currents. Two mechanisms by which crosswind tidal shear may distort and disrupt Langmuir cells are proposed. The first mechanism involves cell shearing due to differential advection across the whole cell. For the second mechanism, middepth vertical LC currents advect sheared mean crosswind current, leading to the attraction of upwelling and downwelling regions, so that LC cells are unsustainable when both regions overlap. Scaling arguments indicate that LC cells are more susceptible to crosswind shear distortion for smaller LC surface velocity convergence and greater cell aspect ratio (vertical to horizontal LC scale), which is consistent with the results obtained from the observations and LES. These results imply that scaling of LC characteristics in a coastal ocean differs from that in the open ocean, which has important practical implications for parameterizing enhanced mixing due to LC.
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): C08005, doi:10.1029/2011JC006971.
Suggested CitationJournal of Geophysical Research 116 (2011): C08005
Showing items related by title, author, creator and subject.
Scully, Malcolm E.; Fisher, Alexander W.; Suttles, Steven E.; Sanford, Lawrence P.; Boicourt, William C. (American Meteorological Society, 2015-10)Measurements made as part of a large-scale experiment to examine wind-driven circulation and mixing in Chesapeake Bay demonstrate that circulations consistent with Langmuir circulation play an important role in surface ...
Significance of Langmuir circulation in upper ocean mixing : comparison of observations and simulations Kukulka, Tobias; Plueddemann, Albert J.; Trowbridge, John H.; Sullivan, Peter P. (American Geophysical Union, 2009-05-28)Representing upper ocean turbulence accurately in models remains a great challenge for improving weather and climate projections. Langmuir circulation (LC) is a turbulent process driven by wind and surface waves that plays ...
Gnanadesikan, Anand (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1994-09)This work investigates whether large-scale coherent vortex structures driven by wave-current interaction (Langmuir circulation) are responsible for maintaining the oceanic mixed layer. Langmuir circulations dominate the ...