Tidal variability of headland eddy shedding


The Sally Ride and Oceanus are both wrapping up long (36-48 hour) repeat sections down here at Pt. Sal before heading back to Oceano. Following up on the Sounder post below, we have also been intrigued by the strongly time-dependent nature of the wake eddies being shed south of Pt. Sal.

The figure above shows 15 passes around our “L” shaped Sally Ride pattern, with local time given at the top. Color is SST and arrows are depth-averaged currents.

During and following periods of strongly southward (tidal+mean) flow, e.g. the second and third panels, an energetic recirculation eddy results on the onshore end, consistent with small boat measurements reported below. Related (somehow!) to these recirculations, there is a frequently occurring clear front (red to blue colors).  At times it seems clear that the sharpness of this front is related to convergences between separated southward flow and recirculation eddies, for example in panel 13. At other times, the structure and location of both the density fronts and the current patterns seem a tad mysterious.

We can only imagine that once we collectively integrate measurements from all seven ships! (3 big, 3 small) plus drifters!  into this pattern, the nature of the flow will either be even more mind-blowingily confusing, or magically crystal clear. So much fun analysis to look forward to.