The last boat afloat

Though most of our friends have left, the science crew of the Sally Ride has been enjoying our final few days of surveying.   Some of the topics that have been on our mind this week include wakes associated with flow around topography, strong fronts created by confluence in these wakes, or by confluences in the generally eddying along-shore flow, and how any of that structured momentum and buoyancy variance is ultimately dissipated.

Here are a few examples. First we have a composite of 24 hours of repeat occupations of an “L” pattern near Pt Sal.   The flow (black arrows) not only changes significantly over a tidal cycle, but shows a variety of small-scale eddies to boot.  Bow chain temperature (color) shows a wealth of features, including trains of incoming solitary waves as well as sharp fronts likely associated with the topographic wakes. This was from the same time period we had ALL SEVEN (!) large and small boats operating in the vicinity, and we are very excited to work with everyone to fill out this map.



A zoom in on one front near Pt Sal shows it to be incredibly sharp, only a couple meters wide at most (top panel) with elevated turbulence on one side of the front (middle panel), and complex turbulent structures visible in biosonics (lowest panel). [courtesy Ata Suanda, Anna Savage, Sean Haney].

Many of these very sharp, strong fronts were also observed with the GusT probes on our bow chain, with high resolution turbulence data remarkably matched to the sharp gradients, suggestive of any number of interesting instabilities [Alexis Kaminski and Jim Moum]

We get a slightly different view of our ocean full of fronts from the air.  The SIO and UW aircraft of course have been giving us excellent birds eye views of all manner of features.  Closer in, an IR camera on a quadcopter shows us a variety of very complex looking frontal structures (image a few hundred meters wide, courtesy of Eric Lo and Amy Waterhouse)


Inspired by some of these interesting features all of the boats observed near Pt Sal, we more recently spent a day and a half sampling near Pt. Purisima, where we observed another strongly eddying flow (details forthcoming). On a roll, and benefiting from the high winds currently blowing us home not being as difficult as expected, we conducted one final compare-and-contrast topographic survey near Pt. Arguello.

Finally, we took some time to conduct several high resolution cross-shore surveys (at Pt. Sal, Pt. Purisima, and Pt. Arguello), which may provide some insight into incident flow characteristics and boundary/validation conditions for our regional modelers.

We’re a few hours out of port, so more from the other side.  Nice working with you all!