Oceanic Heat Content Variability in Eastern Pacific Ocean

During the Eastern Pacific Investigation of Climate (EPIC) in September 2001 sponsored by NSF and NOAA, oceanic current, temperature and salinity profiles were acquired by deploying airborne expendable profilers from research aircraft flights above the warm pool and along the 95oW transect. Based on in situ measurements, an anticyclonic warm eddy was forced by a low-level atmospheric jet over the Gulf of Papagayo earlier in the year. Sequential images from satellite altimetry over a several month interval suggest that the eddy propagated west to southwest at a speed of 13-15 cm s-1 consistent with a Rossby wave. A second aspect of the Eastern Pacific Ocean is the shoaling thermocline to form the Costa Rica Dome. This warm eddy propagated over the warm pool and had a pronounced impact on the isotherm depths and on oceanic heat content (OHC) variability.

Using monthly and seasonal oceanic climatologies, satellite-derived estimates of OHC are compared to those from in situ profiler data as well as TAO mooring measurements in the Eastern Pacific Ocean during EPIC. While OHC values are much less (50 KJ cm-2) than in the western Atlantic Ocean basins (>100 KJ cm-2), in situ data exhibits more structure in the upper 100 m where observed buoyancy frequencies across the oceanic mixed layer (OML) base are nearly twice as large as those in the Atlantic Ocean basin. These spatial variations have implications for the OML (and OHC) budgets and through shear-induced mixing processes and feedback to the atmosphere (i.e. hurricane Juliette). If models relax back to climatology, temperature and salinity structures will not support realistic density and buoyancy structure, leading to poor predictions of the OML responses that feedback to the atmosphere during strong wind events such as gap winds and hurricanes.