Observations of Surface Mixed Layer Variability in the Eastern South Pacific along the coast of Ecuador

Including the Galapagos Islands in simulations of the equatorial Pacific cold tongue region results in the obstruction of the Equatorial Undercurrent, and may lead to a basin-wide adjustment in the equatorial mass and energy balance (Karnauskas, et al., 2007). Ecuador’s ocean, located in the eastern South Pacific between 2° N - 3° S, and 92° - 80° W, to the immediate east of the Galapagos sheltered from central equatorial processes, and thus exhibits somewhat unique features with a strong economic importance on fisheries in the country. The confluence of distinguishable oceanic currents, meteorological variability influenced by the Inter-tropical convergence Zone, and the local bathymetry create a complex oceanic environment exacerbated by large seasonal and interannual variability. In this work, the variability in surface layer hydrography,, winds and sea surface elevation of the Equatorial South Pacific in the Ecuadorian region, is examined using monthly CTD casts spanning 1992 – 2015 at four re-occupied coastal stations to the north and south of the Equator, as well as casts from annual ship-board cruises (over the same 23 years) along repeated transects extending from the coast to beyond the Galapagos Islands. Observations from the Ecuadorian Sea will be compared with data from NOAA’s Triton Buoy located on the equator to the west of the Galapagos, as well as concurrent sea surface elevation and winds at several sites along the coast and the Galapagos. The monthly coastal observations will be used to examine the interannual variability in surface layer hydrography, and to compare with climate indices for the region. Coastal stations and cruise data will be used to examine the spatial (and temporal) variability of the surface mixed layer across the Ecuadorian Sea. Results will be discussed in terms of episodic changes associated with past El Nino events. This work was supported by the Ecuadorian Secretary of Higher Education, Science, Technology and Innovation.