| Popis: |
Low-frequency circulation over the Texas-Louisiana continental shelf is examined. Currents over the inner shelf are upcoast (Rio Grande to Mississippi River) in summer and downcoast in nonsummer and are driven by an annual cycle of winds. This results in an annual signal for salinity, with lowest salinity waters occurring (a) in late spring along the inner portion of the western shelf when downcoast flows carry the high discharges from the Mississippi-Atchafalya and other rivers to the Mexican border, and (b) in summer over the inner and outer eastern shelf when the upcoast flow causes a pooling of the discharges from the Mississippi-Atchafalya rivers over that shelf. Upcoast winds during summer also result in high salinities over the western shelf due to advection from off Mexico and upwelling. Currents over the outer shelf are variable, but predominantly upcoast throughout the year, probably a result of the integrated effects of anticy-clonic eddies impinging on the shelf edge. Comparison of currents in the weather band (2-10 d) with the mesoscale band (10-100 d) suggests the shelf is divided at approximately the 50-m isobath. The weather band predominates over the inner shelf, reflecting frequent passage of fronts over the region. The mesoscale band predominates over the outer shelf, indicating the presence of offshelf eddies that frequent this region. |
