On the seasonal variability of the currents in the Straits of Florida and Yucatan Channel

Abstract

[1] Seasonal variability in the major passages of the Caribbean are investigated using 5 years of wind and current observations (Explorer of the Seas), combined with a 3 year 1/12° simulation. Seasonal fluctuations in the Florida and Yucatan passages are both characterized by semiannual cycles with transport maxima in summer and winter and minima in spring and fall. In the Straits of Florida, seasonal variability is associated with surface-intensified fluctuations of the Florida Current and can be largely explained by along-channel winds and wind stress curl over the Atlantic Ocean. In the Yucatan Channel, seasonal variability is more barotropic and does not covary with wind forcing but rather is associated with fluctuations of an anticyclonic recirculation to the south of the channel. Upstream, the seasonality in the Grenada Passage also covaries with seasonality in the Yucatan and Florida passages, although the Grenada Passage carries only a small fraction of the total inflow to the Caribbean. Recent in situ estimates of the mean transport in the Yucatan Channel differ by 7 Sv (30.5 Sv, Explorer of the Seas; 23.1 Sv, CANEK). An assessment of sampling errors, biases, and interannual variability seem to account for no more than 2 Sv, leaving no satisfactory explanation for the difference. In Explorer of the Seas data, flows in the Straits of Florida and Yucatan Channel display similar vertical shear structure, while CANEK data exhibit significantly lower shears in the upper 500 m, which account for all the transport difference.