2005 LAYERED OCEAN MODEL WORKSHOP

In this study we analyze the subtropical cells (STC) in the Pacific Ocean using an eddy-resolving HYCOM simulation with varying atmospheric forcing for the years 1992-2003. In particular, we seek to identify decadal changes in the STCs in the model, to compare them with observations, and to understand the consequences of such changes for the equatorial ocean heat and mass budgets. The model simulation shows a trend towards increasing pycnocline volume transport across the basin from 1992 to 2003. This increase is attributed to changes in the interior ocean similar to those observed while variability in the western boundary partially compensates that in the interior. Furthermore, the interannual variability in the heat balance of the equatorial zone (defined as the region between 9N and 9S, and from the surface to the 25.3 isopycnal) is found to be dominated by anomalous meridional volume transport variations rather than anomalous transport of thermal anomalies by the mean circulation. Meridional volume transport anomalies in the model pycnocline are also found to be consistent with anomalous volume transports in both the observed and modeled Equatorial Undercurrent.