Nearshore Response of Mesoscale and Submesoscale Dynamics at Tropical Western Pacific Islands

Abstract: 

Observations from around the island group of Palau, located in the tropical Western Pacific, exhibit a persistent presence of baroclinic coastally trapped waves. The signals are found in records of temperature that were sustained on the fore-reef for seven months, May to December 2013, with the strongest signal from Typhoon Haiyan which passed over Kayangel Atoll, along with the northern most Palauan islands, in November of 2013. This strong forcing led to a large near-and sub-inertial response both in temperature and nearshore currents. The observed phase speeds of the propagating signals in temperature records are within a factor of two of those predicted using multiple modeling techniques which properly account for local stratification, topography and the local Coriolis parameter. The apparent omnipresence of coastally trapped waves throughout the observational window provide a regular cycling of temperature at depth, potentially conditioning the benthic habitat to temperature swings.

The role of synoptic oceanographic processes in driving nearshore flows around Palau are being assessed through in-situ current meters and a network of three remote HF radar stations. Currents and tides in the southern extent of Palau have proven to have a time varying phase relationship. Mapping of the island scale mean flow and vorticity fields have helped to show the spatial structure of these flows helpings to elucidate their forcing.