Speaker: Magdalena Andres (WHOI)
Title: Tidal to Interannual Variability of SSH around Palau: Results from the FLEAT Program
Oceanic processes that have an expression in the ocean’s sea surface height (SSH) occur over time scales ranging from sub-tidal and tidal (with the latter comprising both the baroclinic and the barotropic tides), to processes in which the SSH signals evolve more slowly like during the propagation of baroclinic Rossby waves and mesoscale eddies, to global-scale changes in the mass distribution and heat content of the oceans. We report on SSH variability at timescales ranging from tidal to interannual near Palau, an island at the southern end of the Kyushyu-Palau Ridge in the western North Pacific. Palau sits in the path of the westward-flowing North Equatorial Current (NEC), though under some conditions the current system shifts north and the eastward-flowing North Equatorial Countercurrent (NECC) impinges on the island. We examine the following questions: What are the key drivers of SSH variability by Palau, how much do these processes each contribute to the overall SSH field, and what part of the SSH field is predictable? Further, how do the steep topography and the complicated NEC/NECC system affect the SSH signal propagation near Palau? To address these questions, we use observations from satellite altimetry, tide gauges, and an array of in situ moored instruments that were deployed for 10 months around the northern half of Palau. This array is part of an integrated observational and modeling campaign funded by the U.S. Office of Naval Research, Flow Encountering Abrupt Topography (FLEAT). The overall goals of FLEAT are to investigate (1) processes that drive the down-scale cascade of energy, (2) interactions between the upper and deep ocean, and (3) the role of topography in shaping the flow.