Heat and Freshwater Budgets of the Caribbean Sea with Revised Estimates for the Central American Seas

Abstract

Monthly multi-annual mean heat budgets are calculated for the Caribbean Sea; previous results from the Gulf of Mexico are included to portray fields for the combined Central American seas. Oceanic heat storage rates (QT) for the upper 200 meters in the Caribbean are calculated directly from vertical subsurface temperature data for the decade 1967–76; spatial distribution of QT are contoured on maps for February, May, August and November. In the Gulf of Mexico, QT was found to be determined principally by the surface heat exchange. In the Caribbean Sea, QT is related primarily to convergence and divergence of heat transport; QT patterns in the southern Caribbean can be associated with Ekman pumping and heat advection due to currents. The monthly mean surface heat exchanges are defined by the averages of Bunker's unpublished data and the atlas data of Hastenrath and Lamb. Comparisons are also made with the results of both Budyko and Coló in the Caribbean Sea for historical perspective. Monthly mean oceanic heat transport divergences are then derived as residuals in the heat budget equation. Partial verification is obtained by directly computing the horizontal component of heat advection using estimates of water transport in the Central American seas. Estimates of the seasonal freshwater budgets in the Central American seas are calculated using the oceanic precipitation rates (P) of Dorman and Bourke and the averaged evaporation rates (E) obtained from Bunker and from Hastenrath and Lamb. Annual mean E – P values of 104 and 112 cm are obtained for the Caribbean Sea and Central American seas, respectively. The freshwater continuity is examined by including estimates of river discharge rates; it is shown that river discharge does not compensate for the net water loss caused by an excess of evaporation over precipitation. An analysis of the freshwater flux in the Central American seas, using typical salinity data, indicates a convergence of freshwater over the region consistent with the earlier observation of excessive evaporation.