Wind and eddy-related shelf/slope circulation processes and coastal upwelling in the northwestern gulf of Mexico

Document Type

Article

Publication Date

1-1-2005

Abstract

Wind-and eddy-driven circulation on the Louisiana-Texas shelf and slope are investigated during 1993-1994 by integrating measurements from satellite sensors (sea surface temperature, sea surface height) and in situ measurements from satellite-tracked drifting buoys and midwater shelf current meters. Four distinct circulation regimes were identified during autumn/winter including a down-coast jet on the west Louisiana and Texas inner shelf regions, cross-shelf entrainment within the "Texas jet," seaward entrainment by slope eddies, and weak cyclonic circulation on the outer Louisiana shelf. The inner shelf coastal jet (20-98 cm s-1), associated with strong northeasterly winds, developed between the 10 m and 30 m isobaths seaward of the main sea-surface temperature front. Maximum current speeds were measured along the Texas coast between 29° N and 26° N. Although down-coast flow occurred 80% of the time, current reversals of 1-3 days resulted from northwesterly winds during frontal passages. A high velocity cross-shelf jet (13-59 cm s-1) was identified at 28° N, where an anticyclone/cyclone eddy pair entrained surface drifters onto the slope. During summer, prolonged current reversals with surface velocities of 2 0-5 0 cm s-1 occurred on the Louisiana-Texas shelf as a result of strong southerly wind stress over the south Texas shelf and moderate southerly/southwesterly wind stress over the Louisiana shelf. A ~20-km wide zone of relatively cool waters (23°C-26°C) was detected along the coast between 23° and 28° N, subsequent to the current reversal. In situ measurements over three consecutive summers revealed that this coastal upwelling lasts four to six weeks in summer along the south Texas and north Mexican coast.

Publication Source (Journal or Book title)

Geophysical Monograph Series

First Page

295

Last Page

313

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