Linear and nonlinear stratified spindown over sloping topography
Citable URI
https://hdl.handle.net/1912/3635Location
Middle Atlantic BightDOI
10.1575/1912/3635Keyword
Ocean currents; Ocean circulationAbstract
In a stratified rotating fluid, frictionally driven circulations couple with the buoyancy
field over sloping topography. Analytical and numerical methods are used to quantify
the impact of this coupling on the vertical circulation, spindown of geostrophic flows,
and the formation of a shelfbreak jet.
Over a stratified slope, linear spindown of a geostrophic along-isobath flow induces
cross-isobath Ekman flows. Ekman advection of buoyancy weakens the vertical
circulation and slows spindown. Upslope (downslope) Ekman flows tend to inject (remove)
potential vorticity into (from) the ocean. Momentum advection and nonlinear
buoyancy advection are examined in setting asymmetries in the vertical circulation
and the vertical relative vorticity field. During nonlinear homogeneous spindown over
a flat bottom, momentum advection weakens Ekman pumping and strengthens Ekman
suction, while cyclonic vorticity decays faster than anticyclonic vorticity. During
nonlinear stratified spindown over a slope, nonlinear advection of buoyancy enhances
the asymmetry in Ekman pumping and suction, whereas anticyclonic vorticity can
decay faster than cyclonic vorticity outside of the boundary layers.
During the adjustment of a spatially uniform geostrophic current over a shelfbreak,
coupling between the Ekman flow and the buoyancy field generates Ekman pumping
near the shelfbreak, which leads to the formation of a jet. Scalings are presented for
the upwelling strength, the length scale over which it occurs, and the timescale for
jet formation. The results are applied to the Middle Atlantic Bight shelfbreak.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2010
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Suggested Citation
Thesis: Benthuysen, Jessica A., "Linear and nonlinear stratified spindown over sloping topography", 2010-06, DOI:10.1575/1912/3635, https://hdl.handle.net/1912/3635Related items
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