The Time-varying Characteristics of the Meridional Ekman Heat Transport for the World Ocean

Abstract

The time-varying meridional Ekman heat transport for the World Ocean is calculated for the 30-year period 1960?1989 using wind stress and sea surface temperature data from the Comprehensive Ocean?Atmosphere Data Set The average monthly heat transports are dominated by poleward transport of heat in the tropical Pacific and Atlantic oceans. In the Indian Ocean, the strong monsoonal flow during summer is responsible for a large equatorward transport. If seasonal effects are removed, the tropical Pacific displays the most variance in Ekman heat transport and the Atlantic the least. Two sets of empirical orthogonal functions (EOFs) are computed to investigate the nonseasonal variability of the Ekman transport The first set, which uses the eigenvector decomposition of the covariance matrix, emphasizes covariability in the world's tropical oceans. The time series of the EOF amplitudes contain a clear signal that can be directly related to El Niño. The El Niño signal is manifest as an increase in the equatorward transport of heat in the western Pacific followed by an increase in the poleward transport of heat in the eastern Pacific. The second set of EOFs, which highlights spatial oscillations only, shows the influence of zonal bands of wind stress and the large-scale patterns of Ekman suction/pumping.