Simulation of Ocean Circulation around the Galápagos Archipelago using a HYbrid Coordinate Ocean Model (HYCOM)
Yanyun
Liu, North Carolina State University, yliu10@ncsu.edu
Lian
Xie, North Carolina State University, lian_xie@uncw.edu
John
M.
Morrison, University of North Carolina Wilmington, morrisonj@uncw.edu
(Presenting)
The ocean circulation around the Galápagos Archipelago is simulated using the University of Miami&rsquos Hybrid Coordinate Ocean Model (HYCOM) using a high-resolution (.04-degree resolution) nested domain. Sensitivity studies showed that a resolution of the 0.04 degrees or less is needed to reproduce the major ocean circulation features water mass structure local to the Galápagos. The sensitivity studies also showed that it was necessary to use daily mean interpolated from 25-km resolution QuikSCAT wind fields to adequate reproduce the observed current variability within the Archipelago. The resulting simulations reproduced the large range in temperature and salinity associated with 4 different current systems and topographically and wind forced upwelling. The largest and most persistent upwelling zones were found on the western sides of Isabella and Fernandina Islands, resulting from the collision of the Equatorial Under Current (EUC) with the islands, bring relatively colder and salty waters to the surface in a region of topographically induced upwelling. This upwelling zone marks the location of high-biological production at the surface with the EUC shoaling to approximately 20m from its normal depth of 50m just to the west of the islands. Other sensitivity studies show that HYCOM uncoupled to an atmospheric model, but driven by high-resolution winds, reliably simulates ENSO variability. Further diagnostic studies will focus on oceanographic variability and the response of the ocean ecosystem around the Galápagos. Case studies will be used to study how El Niño/La Niña events affect the Galapagos Archipelago. These will include hind-casts during strong El Niño and La Niña conditions, as well as periods of &ldquonormal&rdquo conditions. We will study the relationship between the path of the EUC through the Archipelago and the effects of Tropical Instability Waves (TIW) on upwelling and biological productivity with the Galápagos.
This project was supported by NASA&rsquos Biodiversity and Ecological Forecasting grant NNG04GL98G
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