Model-calculated seasonal transport variations through the Florida straits: a comparison using different wind-stress climatologies

A linear, barotropic model of the North Atlantic at 1 degree x 1 degree resolution is employed to investigate the effect of using different wind-stress climatologies on the model response at the Florida Straits. The wind-stress climatologies are those of da Silva et al. (DS), Hellerman and Rosenstein (HR), Isemer and Hasse (IH), and Trenberth et al. (TR). For each climatology, the model shows maximum northward transport in the summer and minima in the fall and late winter, in general agreement with transport measurements from cable data (Larsen). However, the amplitude of the model response differs considerably between the climatologies. In the case of DS the range (maximum transport minus minimum transport) is 2.8 Sv; HR: 3.6 Sv, TR: 5.2 Sv, and IH: 5.9 Sv, compared to a range of 4.6 plus or minus 0.3 Sv derived from cable data. The increased range in the IH case compared to HR is in general agreement with the finding of Boning et al. using the Kiel version of the model that forms the WOCE Community Modelling Effort. However, whereas Boning et al. claim that winds north of 35 degree N have little influence on the seasonal response of their model at the Florida Straits, it is found that winds north of 35 degree N play an important role in the model presented here. The reason for the behavior of the community model is not clear but may be associated with advection by the western boundary current, an effect not present in the linear model discussed here. In the case of the present model, the importance of forcing by the meridional component of the wind is shown, although forcing through the zonal component also plays some role in explaining the differences between the cases run under the different climatologies. The importance in the model of forcing associated with the meridional component of the wind along the continental slope region to the north of the straits is emphasized.