Figure 8. Time series of monthly mean rainfall (upper) and monthly rainfall anomaly (lower) averaged over the rectangle in Fig. 7. The heavy line is a spline fit.
This decadal variation seems relatively small in comparison to the intraseasonal variability, but it is over a large area of the ocean, and the anomalies persist for several years. Thus, we may expect that there will be a cumulative impact on upper ocean salinity.
The mixed layer T-S conditions which are imprinted on the upper pycnocline are those at the time of deepest mixing (Stommel, 1979), giving rise to a very nonlinear relationship between low frequency variations in upper pycnocline T-S characteristics and the high frequency forcing associated with winter storms. While monthly observations are not sufficient to resolve all of the important forcing, they can give us some insight. Because of the variable timing of the maximum precipitation, we average the January through March observations as a gross indicator of the “winter imprint” on the subduction process.
