Daily Archives: September 11, 2017

Tidal Bore and Soliton tracking on Oceano

Sally Ride is tracking tidal bores and internal solitary waves (ISWs) on the Oceano array today and through the night on a small southern box between the 20 and 50m isobaths. Our box coordinates are

SRSW 34 58.241,  120 44.448

SRSE   34 57.912,  120 41.031

SRNE   34 58.795,  120 40.086

SRNW 34 59.211,  120 44.251

 

After a tumultuous night of lightning and rain we were greeted by an inspiring sun rise.

 

Our survey instrumentation includes a CTD bow chain down to 20-m depth, a bow mounted IR camera and radiometer, a pole mounted 500 kHz ADCP, 120 and 200 kHz echo sounders, and a vertical microstructure profiler (VMP).

The observations are revealing interesting internal structure of the ISWs, as seen by the echo sounders.

[Caption: Internal Bolus? Colliding ISWs? Biological Scatter?]

Also, significant lateral small-scale variability of the waves is seen by this opposing and following cross section of an ISW wave train. The opposing and following transects are separated by 100-200m along the wave crest.

 

The waves appear to be coming from both the WNW and WSW and are traveling at an average speed of 25 to 30 cm/s. VMP and Bow chain results forth coming!

 

 

 

IOP1 Drifter Trajectories

On Sunday, we had the first day of IOP1 operations near Pt Sal.   The Sally Ann and RV Sounder joined forces around the headland.  It was a beautiful day at the point as it almost always is.  The Pt itself was intermittently shrouded by marine fog, below is a view from the bay south of the point.

The drifters were “Davis” style drifters – see photo below, and are based on drifter designs from the 1980s.   The update here is that the drifter tracking uses “spot” technology to get a GPS fix every 2-3 minutes.  This data is then beamed back to Matt’s cell phone so that we can see where they are at all times.  This realtime tracking makes drifter releases in wild settings such as Pt Sal feasible.   We can grab them before they run aground.

We deployed a sequence of 27 drifters to the north Pt Sal.    Drifters were released in 3 clusters of 9 drifters making the shape of a cross.  Jim Thomson placed two SWIFT drifters in the center of each drifter grouping. We allowed the drifters to roam for about 4 hours while we surveyed with ADCP and CTD along w/ the RV Sounder.  Below are the drifter trajectories on top of the bathymetry contours.   Each cross pattern went offshore at first and then onshore.   Most crosses went south and rotated (see the red and yellow/green) indicating the drifters were embedded in an eddy.    This drifter release pattern was repeated again today (11-Sept).

The BAT flies!

Today on R/V Oceanus we got the Acrobat flying with its two GusT probes sticking out front. We’re using it to survey a flux box around the Oceano array. It takes us about 3 hours to go around it at 5 knots. Before we started BATing — oh, by the way, there’s a real bat with us on Oceanus, likely a stowaway from Oregon — we did a 2-knot CTD tow-yo/ADCP run in parallel with R/V Kalipi. They ran a 10-m line inshore of us, but, as in their post, it was a little too shallow for operations. So they moved to the 15-m isobath that is shown as the dashed line in the box below.

This evening we had a great lightening display off to the east. We did get a brief wind burst and rain shower, just before which we recovered the BAT in case the Oceanus captain had to maneuver quickly. Here’s what the storm looked like on the UMiami Marine Doppler Radar onboard Oceanus (courtesy of Lisa Nyman). On the left is a nice image of NLIWs, on the right is the storm.

We’ll keep BATing until tomorrow and look for a time to do a slower, detailed, 2-knot cross-shore chase of NLIWs with the Sally Ride.

—Jack Barth, R/V Oceanus

Alongshore transects

Today the Kalipi raced the Oceanus in an all out battle for data. We ran transects parallel to the Oceanus, surveying with a side-mounted ADCP and fast profiling CTD. During our transect along the 10 m isobath, we encountered some surprising suddenly shallow regions, so our second transect was moved to the 15 m isobath, where we managed to finally “catch” something after “fishing” all day—a brief snag on something on the bottom. But all was well, and we successfully completed two transects before heading in to avoid potential thunderstorms.

“That Oceanus will never catch us!” -Jenny

Keeping a close eye on our competition: the Oceanus from afar.

Jim fishes for data with the fast profiling CTD. Fish on!

-Jenny Thomas (all photos: Taylor Eaton)

scripps oceanography uc san diego