ACCP Accomplishments

Mean and time-dependent properties of the meridional overturning circulation have been defined. In the lower layer, the continuity of the Deep Western Boundary Current (DWBC) from 26.5N to the equator has been documented. The intensity of the DWBC as determined from direct measurements is significantly greater than estimated previously. A portion of this excess transport has been attributed to both local and large-scale recirculation gyres, located offshore of the boundary. The time-dependent water mass characteristics of the DWBC have been estimated from a 14-year record obtained east of the Bahamas at 26.5N. A 1994 intrusion of waters recently ventilated in the Labrador Sea was identified. The estimated advective time from the Labrador Sea is considerably shorter than earlier findings suggesting a more intense meridional overturning circulation.

In the upper layer, the mean and time-dependent properties of the warm return portion of the overturning circulation have been studied. Near the equator, the blending of southern and northern hemisphere waters along the western boundary have been shown to impact on cross-equatorial exchanges. The introduction of tropical waters into the subtropical Atlantic through the Caribbean has been shown to be less intense than previously estimated. These observations support numerical modeling results.

Decadal variability in the upper layer temperature structure of the western subtropical North Atlantic has been quantified. Comparisons of numerical model results with these observations show many similarities. In particular, the modeled and observed structure of coherent sea-level pressure and subsurface temperature variability are similar.

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