Publication Date:
2022-05-26
Description:
Author Posting. © American Geophysical Union, 2010. 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 115 (2010): C12023, doi:10.1029/2009JC005578.
Description:
The subtidal, depth-average momentum balances in 12 m and 27 m water depth are investigated using observations from 2001 to 2007 of water velocity, temperature, and density; bottom pressure; surface gravity waves; and wind stress. In the fluctuating across-shelf momentum budget, the dominant terms are surface wind stress, pressure gradient, and Coriolis acceleration. The balance is a combination of (1) the geostrophic balance expected at midshelf sites and (2) the coastal setup and setdown balance driven by the across-shelf wind stress expected where surface and bottom boundary layers overlap. At the 12 m site, the estimated wave radiation stress gradient due to surface gravity wave shoaling is also large but is uncorrelated with the observed pressure gradient. A simple model suggests the wave radiation stress gradient is balanced by an across-shelf pressure gradient with a spatial scale too small to resolve with this mooring array. In the fluctuating along-shelf momentum balance, the dominant terms are surface wind stress, pressure gradient, and bottom stress at the shallower site, but the other estimated terms are not negligible. Our results support the Grant and Madsen (1986) formulation for wave-induced bottom stress. The fluctuating along-shelf pressure gradient is mainly a local sea level response to wind forcing, not a remotely generated pressure gradient. A strong correlation between along-shelf velocity and along-shelf wind stress at the shallower site is captured by a simple steady model of imbalance between wind stress and pressure gradient balanced by linear bottom drag.
Description:
This research was funded by the Ocean Sciences
Division of the National Science Foundation under grants OCE‐
0241292 and OCE‐0548961 and by the National Aeronautics and Space
Administration Headquarters under grant NNG04GL03G and the Earth
System Science Fellowship grant NNG04GQ14H. MVCO is partly funded
by the Woods Hole Oceanographic Institution and the Jewett/EDUC/
Harrison Foundation. CBLAST 2003 was funded by the Office of Naval
Research contracts N00014‐01‐1‐0029 and N00014‐05‐10090 for the
Low‐Wind Component of the Coupled Boundary Layers Air‐Sea Transfer
Experiment. The F ADCP, T1 and T2 moorings, and temperature
measurements near the Node in 2003 were funded by the National Science
Foundation Small Grant for Exploratory Research OCE‐0337892
(“Observational Mesoscale Context for Oceanic Turbulence Measurements
Obtained during CBLAST‐Low”).
Keywords:
Inner shelf
;
Momentum budget
;
Coastal
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
