Strongly-sheared wind-forced currents in the nearshore regions of the central Southern California Bight

Continental Shelf Research
By: , and 

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Abstract

Contrary to many previous reports, winds do drive currents along the shelf in the central portion of the Southern California Bight (SCB). Winds off Huntington Beach CA are the dominant forcing for currents over the nearshore region of the shelf (water depths less than 20 m). Winds control about 50–70% of the energy in nearshore alongshelf surface currents. The wind-driven current amplitudes are also anomalously high. For a relatively weak 1 dyne/cm2 wind stress, the alongshelf surface current amplitudes in this region can reach 80 cm/s or more. Mid-depth current amplitudes for the same wind stress are around 30–40 cm/s. These wind-driven surface current amplitudes are much larger than previously measured over other nearshore shelf regions, perhaps because this program is one of the few that measured currents within a meter of the surface. The near-bed cross-shelf currents over the nearshore region of the Huntington Beach shelf have an Ekman response to winds in that they upwell (downwell) for down (up) coast winds. This response disappears further offshore. Hence, there is upwelling in the SCB, but it does not occur across the entire shelf. Subthermocline water in the nearshore region that may contain nutrients and plankton move onshore when winds are southeastward, but subthermocline water over the shelf break is not transported to the beach. The currents over the outer shelf are not predominately controlled by winds, consistent with previous reports. Instead, they are mainly driven by cross-shelf pressure gradients that are independent of local wind stress.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Strongly-sheared wind-forced currents in the nearshore regions of the central Southern California Bight
Series title Continental Shelf Research
DOI 10.1016/j.csr.2015.04.019
Volume 106
Year Published 2015
Language English
Publisher Elsevier
Contributing office(s) Pacific Coastal and Marine Science Center
Description 16 p.
First page 1
Last page 16
Country United States
State California
Online Only (Y/N) N
Additional Online Files (Y/N) N