Flow Encountering Abrupt Topography - FLEAT

The ONR-funded project FLEAT aimed at studying interactions of mean-flow and topography in the vicinity of Palau. A guiding research question for this project was: How are energy and momentum of mean and meso-scale flow affected by interactions with bathymetry?

The island group of Palau in the tropical North Pacific provided an ideal natural laboratory - steep topography and strong currents made for an exciting experiment site. On a cruise in June 2016 we deployed moorings and carried out shipboard measurements with various instruments to study the generation of lee waves and lee vortices as the flow interacted with the northern end of Palau. We recovered all moorings during a second cruise in June 2017 and collected shipboard measurements of topographic lee waves over Yap Ridge to the northeast of Palau.

Based on towed CTD/LADCP sections and data from a mooring we published a study on topographic lee waves generated by low-frequency and tidal flows over the tall and steep submarine ridge north of Palau. The paper examines the generation and breaking of internal waves and their effective drag on the background flow.

A paper led by Jen MacKinnon focused on the generation of wake eddies via a combination of low-frequency and tidal flow at the northern tip of Palau. Using a combination of fastCTD towed sections, turbulence profiles, and mooring data, the paper shows how the presence of tides can boost the generation of small-scale vorticity which leads to increased export of vorticity into the larger-scale island wake. Using the same dataset, a paper led by Bethan Wynne-Cattanach explored the relationship between vorticity, layered flow, and turbulent mixing.

More papers resulting from the FLEAT project can be found in a special issue of Oceanography and in the JPO special collection on Oceanic Flow-Topography Interactions.