Onshore and offshore currents prevailed in 

 the fall and probably late spring. 



• Surface currents were generally easterly in 

 the summer (0.40 knots) and westerly from 

 winter through early spring (0.82 knots). 



'Mid-depth currents (0.26 knots) were 



easterly, onshore and offshore in the summer; 



westerly and offshore from winter through 

 early spring. 



•Bottom currents (0.22 knots) were mostly 

 onshore and easterly in the summer; westerly, 

 onshore and offshore from winter through 

 early spring. 



•Current speed decreased with depth. 



•The net annual movement of water in the study 

 area was westerly. 



These determinations were consistent with the findings of current 

 studies performed offshore Galveston in the Buccaneer Gas and Oil Field 

 (BG0F) by Armstrong (1979). Currents in the BG0F were found to be 

 aligned principally in long-shore directions, reversing seasonally from 

 upcoast toward the northeast in summer (May- August) to downcoast toward 

 southwest for October- April. Transitional conditions appeared to rule 

 in September and April. Current meter records showed layering of 

 contrasting flows during some seasons. Local winds were apparently the 

 main driving force for the circulation. Flow was typically with the 

 wind but was deflected by the coastline such that there was compensating 

 offshore transport with onshore winds, or to the right of the winds due 

 to Ekman transport. Distinct departures from local wind-driven 

 circulation developed during spring, when it seems high river discharge 

 established a downcoast, geostrophic current which, from current meter 

 records, may have accounted for the layered currents of summer. Also, 

 during early fall, currents of the area did not appear to relate to 

 local winds, but may have been responding to larger-scale atmospheric 

 alterations. Spectral analyses of current meter records indicated that 

 tidal currents and wind shifts accounted for most of the variability in 

 flow dynamics, with dominant periods perhaps associated with passage of 

 continental air masses in winter and fall, and longer-period maritime 

 air mass development during summer. 



The Brownsville Gyre is a prominent and important feature of the 

 circulation in the southwestern portion of the Texas-Louisiana shelf 



10 



