Analysis of Interannual Variability in the Eastern Equatorial Pacific Ocean Using a High Resolution Regional Ocean Modeling System

Interannual variability in the Eastern Equatorial Pacific Ocean is explored using a high resolution ocean model. The model domain covers the coast of South America to 96°W, including the Galapagos Islands, and from 15°S to 15°N. An experiment based on a run from January 1990 to December 1999 is conducted using the Simple Ocean Data Assimilation version sparse input.2 (SODAsi.2) 5 day data sets for the initial and boundary conditions. For surface forcing the 20CRV2 (20th Century Reanalysis version 2) daily data set is used. The model results are compared with observations from a buoy that is part of the Tropical Atmosphere Ocean (TAO) project located at 95°W and over the equator, the model captures the main features of annual and interannual variability, although there are some notable discrepancies. At the surface we can identify the most important features of the domain of study that are the equatorial cold tongue, the Costa Rica Dome and the east Pacific warm pool. In the subsurface the thermal distribution agrees with the typical behavior of the east Pacific Ocean such as strong stratification and a shallow thermocline. The results show strong anomalies of sea surface temperature (SST) and sea surface height (SSH) during El Niño. Changes in conditions at the surface and subsurface demonstrate the strength of the 97-98 El Niño event, especially when compared with the weaker 1991-92 event. The results are also used to explore changes in circulation around the Galapagos during El Niño