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Equatorial Ocean Dynamics Impacting Upwelling West of the Galápagos Archipelago

Julie Jakoboski, Ph.D., 2019
W. Brechner Owens, Co-Advisor
Robert E. Todd, Co-Advisor
Kristopher B. Karnauskas

The Galápagos Cold Pool (GCP), a region of anomalously cold sea surface temperature (SST) just west of the Galápagos Archipelago, is maintained by wind- and current-driven upwelling.  The Pacific Equatorial Undercurrent (EUC) may upwell into the GCP as it reaches the topographical barrier of the Galápagos Archipelago.  The “Repeat Observations by Gliders in the Equatorial Region” (ROGER) program deployed a fleet of Spray gliders in the region of the GCP from 2013–2016 and obtained subsurface measurements of temperature, salinity, and velocity with unprecedented temporal and spatial resolution.  These measurements are used to observe the path of the EUC as it bifurcates into north and south branches around the Galápagos Archipelago.  Net horizontal transport is used to estimate an average vertical velocity profile in the region of the GCP, indicating upwelling in the upper 300 m.  The bifurcation latitude of the EUC is meridionally aligned with the center of the archipelago, suggesting the bifurcation latitude is topographically controlled.  Sections of Ertel potential vorticity and Bernoulli function support an inertial model of the EUC.  Average spectral variance from Argo profiling float observations shows that tropical instability waves propagate with frequency and wavelength consistent with model results and may impact the GCP.