Occasionally, there is positive zonal advection near sea surface, but it is not dominant in the 0-50 m average. The zonal and meridional advective terms are much smaller during cruise 3 owing to the relatively weak horizontal temperature gradients. The 3-D budget estimate compares much better with the observations. The eddy advection here refers to heat advection due to sub-cruise time scale activity. The mean advection represents heat advection due to the ISO and longer time scale variability.
Meridional advection dominates in both the mean and eddy advection.
During cruise 3, the large vertical advection is dominated by eddy term. Overall, the heat advection due to inertial motions is comparable with or larger than the contributions from the ISO and longer time scale variability. The other difference is that the multi-peak WWB induced inertial motions, which contribute significantly to the heat budget, were not resolved in the weekly SST advection calculation. During cruise 2, zonal advection brings in saltier water before January 1 and reverses sign after that. During cruise 2, meridional advection is dominated by the two episodes of northward inertial currents in the surface layer, which consistently bring saltier water from the south.