Buoyancy arrest and bottom Ekman transport. Part I : steady flow
MetadataShow full item record
It is well known that along-isobath flow above a sloping bottom gives rise to cross-isobath Ekman transport and therefore sets up horizontal density gradients if the ocean is stratified. These transports in turn eventually bring the along-isobath bottom velocity, hence bottom stress, to rest (“buoyancy arrest”) simply by means of the thermal wind shear. This problem is revisited here. A modified expression for Ekman transport is rationalized, and general expressions for buoyancy arrest time scales are presented. Theory and numerical calculations are used to define a new formula for boundary layer thickness for the case of downslope Ekman transport, where a thick, weakly stratified arrested boundary layer results. For upslope Ekman transport, where advection leads to enhanced stability, expressions are derived for both the weakly sloping (in the sense of slope Burger number s = αN/f, where α is the bottom slope, N is the interior buoyancy frequency, and f is the Coriolis parameter) case where a capped boundary layer evolves and the larger s case where a nearly linearly stratified boundary layer joins smoothly to the interior density profile. Consistent estimates for the buoyancy arrest time scale are found for each case.
Author Posting. © American Meteorological Society, 2010. 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 40 (2010): 621-635, doi:10.1175/2009JPO4266.1.
Suggested CitationArticle: Brink, Kenneth H., Lentz, Steven J., "Buoyancy arrest and bottom Ekman transport. Part I : steady flow", Journal of Physical Oceanography 40 (2010): 621-635, DOI:10.1175/2009JPO4266.1, https://hdl.handle.net/1912/3959
Showing items related by title, author, creator and subject.
Brink, Kenneth H.; Lentz, Steven J. (American Meteorological Society, 2010-04)The effects of a sloping bottom and stratification on a turbulent bottom boundary layer are investigated for cases where the interior flow oscillates monochromatically with frequency ω. At higher frequencies, or small slope ...
Forsyth, Jacob S. T.; Gawarkiewicz, Glen G.; Andres, Magdalena; Chen, Ke (John Wiley & Sons, 2018-09-12)During the seasonal evolution of stratification on the New Jersey shelf in the fall, strong thermal stratification that was established in the preceding summer is broken down through wind‐driven processes and surface ...
du Plessis, Marcel; Swart, Sebastiaan; Ansorge, Isabelle; Mahadevan, Amala (John Wiley & Sons, 2017-04-08)Traditionally, the mechanism driving the seasonal restratification of the Southern Ocean mixed layer (ML) is thought to be the onset of springtime warming. Recent developments in numerical modeling and North Atlantic ...