Island wakes often have a significant influence on regional current variability and theycan be a strong source of vorticity far from the boundaries of major ocean basins. Historically
they have been difficult to characterize due to the wide range of flow scales which contribute
to their variance. In this thesis work, observations from gliders, moorings, and surface drifters
are combined to investigate the vorticity wake behind Palau, a ~200 km long island in the deep
tropical North Pacific.
First, the island-scale (>30 km) flow is characterized using velocity data obtained with
underwater gliders which profiled along two parallel meridional sections upstream and downstream of the island. On average, westward flow is topographically blocked, accelerates around
the island, and there is recirculation in the lee with vertical vorticity up to 0.3 f . Here f is the
local Coriolis frequency. However, vorticity variance is high and instantaneous values can exceed
f when the incident flow is strongest.
Then, a triangular array of moorings (7 km) deployed within a few km of the north end
of the island is used to capture submesoscale vorticity as it is injected into the wake. At this
scale, vorticity can exceed 6 f during strong westward flow. This vorticity is associated with the
formation of strong wake eddies. We find that tidal and inertial currents heavily modulate the
frequency of eddy formation, even during strong low-frequency flow.
Finally, vorticity downstream of Palau is investigated with clusters of surface drifters
deployed in the same location as the mooring array. Drifters were often entrained in submesoscale
wake eddies with vorticity up to 6 f , consistent with observations from the moorings. Outside
the eddy cores, vorticity is inversely proportional to cluster scale and we conclude the growth of
wake eddies is controlled by large-scale shear in the regional currents.