The North Atlantic Oscillation (NAO) is a dominant climate signal on decadal time scales. It has great impacts, according to observation, on the supolar North Atlantic Ocean, particularly on the formation of the North Atlantic Deep Water (NADW). Its role in climate variability in the tropical Atlantic Ocean is less clear. By using a three-dimensional ocean model and by examining COADS dataset, we found that decadal variation of the sea surface temperature (SST) in the equatorial Atlantic Ocean follows closely, with a lag of 5 years, with the temporal change of the observed Labrador Sea Water Thickness (LSWT). Statistical analysis reveals that the correlation between the tropical Atlantic SST and LSWT is particularly high in the region off the western boundary where the cross-equator flow takes place. It was found that the thermohaline overturning circulation is primarily responsible for this subpolar-tropical teleconnection.