Observed horizontal temperature advection by Tropical Instability Waves

Velocity data from moored current meters is combined with satellite sea surface temperature (SST) to compute oceanic mixed layer temperature advection by Tropical Instability Waves (TIWs). For the years 2002 to 2005 it is found that this process heats the equatorial mixed layer at an annual mean rate of + 0.8 ◦C/month at 0◦N, 140◦W and + 2.8 ◦C/month at 0◦N, 110◦W. At 0◦N, 110◦W, approximately 25 % of the heating is contributed by zonal temperature advection, a process that has often been assumed to be negligible. From a nine month segment of data (May 2004 February 2005), the zonal temperature advection at 2N, 140W has been estimated to be approximately 0.7 ◦C/month, much larger than the equatorial value for the same time period. Thus, the data supports a recent hypothesis that tropical instability waves contribute a significant mean zonal temperature advection with off-equatorial maxima to the equatorial mixed-layer heat budget. Comparisons with numerical model results suggest that current ocean general circulation models can realistically simulate important aspects of tropical eddy-mixed layer interactions.