Response of the West Florida Shelf circulation to climatological wind stress forcing

Abstract

Abstract. The response of the west Florida continental shelf circulation to monthly mean climatological wind forcing is investigated by using the three-dimensional, primitive equation Princeton Ocean Model. Two basic seasonal patterns of circulation and sea surface elevation occur under a barotropic setting: a winter pattern from October to March and a summer pattern from April to September. An interesting finding in winter is an anticyclonic gyre over the northeastern (Florida Big Bend) region that merges with a northwestward flow from the south. The Big Bend Gyre is caused by a convergence of two separate flows: a nearshore along-shelf southeastward flow and an offshore northwestward flow. Winter circulation characteristics also include offshore surface transport, coastal upwelling, and relatively low coastal sea level. The summer pattern features a continuous northwestward directed flow, onshore surface transport, coastal downwelling, and relatively high coastal sea level. Transitions between the two seasonal patterns show either a development or rela,xation of the Big Bend Gyre. These three-dimensional circulation patterns result from wind-driven Ekman transports and their resulting surface-slope-induced geostrophic flows. Qualitative agreement exists in some respects with recent in situ observations, historical drift bottle retrievals, and tide gauge data. However, climatological wind stress forcing alone does not account for the seasonally varying southeastward currents observed at midshelf. Thus it may be concluded that for depths less than 50m the seasonal winds rnay play a dominant role in the seasonal varia, tion of the shelf circulation; and beyond this limit seasonal density related effect must also be a factor in the seasonally varying circulation on the West Florida Shelf.

Cross-shelf transport of pink shrimp larvae: interactions of tidal currents, larval vertical migrations and internal tides

“…7C,D , respectively. This result is consistent with the winds reported for the SWF shelf in summer (Yang & Weisberg 1999). On July 4 the alongshore wind stress intensified and changed direction for a few hours, but with no effect on surface currents or water temperature (Fig.…”

“…Coldwater anomalies often occur as a result of upwelling favorable winds (Weisberg et al 1996), cyclonic gyre circulation (Lee et al 2002), internal tides (Baines 1986) or internal bores (Leichter et al 1996). Winds during the sampling period were weak and mainly from the eastsoutheast, which did not favor coastal upwelling, and were consistent with the winds reported for the SWF shelf in summer (Yang & Weisberg 1999). Cyclonic gyres are common features formed southwest of the Dry Tortugas (Lee et al 1994), which can propagate downstream as transient coastal eddies along the edge of the Florida Keys shelf (Fratantoni et al 1998).…”

Oceanic upwelling and downwelling processes in waters off the west coast of India

“…The T and S are held unchanged during the integration period. When the wind forcing is applied, the velocity field will respond and results in establishing a combined Ekman and geostrophic balance (Blumberg and Mellor 1983;Yang and Weisberg 1999). The model in the diagnostic mode is initially integrated for 25 days until the kinetic energy of the system achieves nearly a steady state .…”

“…For this, the Princeton Ocean Model (POM) is implemented for the west coast of India. The POM is earlier used to study different coastal regions including the west Florida continental shelf circulation (Yang and Weisberg 1999), upwelling off the northern California continental shelf (Gan and Allen 2002), and winter and pre-monsoon surface cooling near the Indian southern tip region (Luis and Kawamura 2002a, b). …”

Relative Humidity over the West Florida Continental Shelf

“…For example, a seasonal midshelf cold tongue develops in spring as baroclinic pressure gradients are induced in response to temperature gradients formed by differential along and across shelf heating (Weisberg et al 1996;He and Weisberg 2002). Model studies have demonstrated a climatological wind-driven preference for wintertime upwelling and summertime downwelling in the northeastern shelf (Yang and Weisberg 1999). A review of the distribution of our instrumentation over the WFS shows that our IMET/ASIMET sensors are situated closest to the coast and farthest north, while the Weatherpak sensors are farther offshore and south.…”