Influence of Tropical Instability Waves on the Pacific Equatorial Undercurrent and Topographic Upwelling West of the Galápagos Archipelago

Topographic upwelling just west of the Galápagos Islands results in a local region of relatively cold sea surface temperature (SST) and high productivity that has significant impacts on the Galápagos Archipelago ecosystem. The archipelago sits directly in the path of the Equatorial Undercurrent (EUC) as it flows from west to east across the Pacific Ocean on the equator. Consequently, the EUC affects the upwelling-fed cold pool and its physical as well as biogeochemical properties on various time scales. Analysis of variability in the SST of the Galápagos cold pool over a twenty-year coupled ocean-atmosphere model run shows variability associated with westward-propagating Tropical Instability Waves (TIWs). Characteristics of the propagation signal from the model run are compared to observations, confirming the presence of reasonability realistic TIWs in the model. The physical interaction between TIW propagation and Galápagos cold pool SST is examined in the coupled model results, using the EUC as a potential mechanism to transmit the effects of local TIW-induced perturbations to the topographic upwelling and cold pool SST, productivity, etc. This mechanism is examined through comparing a timeseries representing the TIW signal with various other metrics, such as EUC strength, latitude, and depth, as well as regional SST. Future work will compare these model results to observational data gathered by autonomous underwater vehicles (AUVs) including Spray gliders deployed near the Galápagos Islands.