The objectives of this project are to quantify the variability in the position and strength of the Pacific Equatorial Front and Equatorial Undercurrent (EUC), and the partitioning of flow around the Galapagos Archipelago. The field work will consist of three sustained high-resolution glider transects to assess variability of the Equatorial Current System, including the obstruction of the EUC by the Galapagos Archipelago. A section at 93W will be representative of the EUC and equatorial front to the west of the Archipelago, and two sections connecting the northern and southern ends of this section to the Archipelago will quantify how the EUC is partitioned into pathways. Using four gliders, each section will be repeated every 10 days, thus barely resolving tropical instability wave variability at a period of 20 days. Spray gliders equipped with CTD and ADPs will profile to 500 m every 3 hours, covering 3 km during the dive cycle. Scientific analyses, including the interpretation of the observations using a new high-resolution model, will focus on quantifying the temporal evolution on scales from seasons to weeks in the Equatorial Current System down to horizontal scales of 10 km. Estimates will be made of horizontal fluxes of mass, heat, and salt. The pathway of the EUC will be determined. Observations will be compared and analyzed with a hierarchy of extant numerical models of the Equatorial Current System and an ongoing data assimilation analysis of the Equatorial Pacific.
Broader Impacts
Available observations do not yet provide an adequate description of the submesoscale structure and variability of the Equatorial Current System or the EUC termination, which remains a major limitation to constraining models and understanding one of the world's most dynamic ecosystems. The proposed systematic and sustained observational program will produce data to be used in a state estimate of the tropical Pacific following recommended best practices for process studies by integrating models with observations from the start, producing quality-controlled data sets suitable for model validation, and encouraging broad use of the data. One graduate student at each institution will work with these data to increase the scientific expertise in eastern equatorial Pacific measurements and analyses. Results will be broadly disseminated at national and international meetings and in peer-reviewed journals. A Wikipedia page on the dynamics of the EUC suitable for the general public and an observational history of the EUC for Oceanography magazine will be prepared. Collaboration with Equadorian oceanographers will train them in the glider operations and the analysis of the glider data.
