IOP2 fun around Pt Sal

SIO-Whaler Sally Ann on her offshore (west) survey leg passing to the south of Ghost Reef on 10 October. Photo was take by Falk Feddersen from the RV Sounder

 

IOP2 has been a great deal of fun all around sampling both Pt Sal and Oceano with the Sounder, Kalipi and Oceanus.  Speaking of Oceanus, On 14 Oct, Mike Kovatch took some cool photos on of her from east of Pt Sal looking between Lion Rock on the left and Pt Sal on the right as the Oceanus was doing her onshore leg  and making the turn. 

 

We had three great days at Pt Sal and below are some plot of both the first day (9 Oct) and the last day (14 Oct).    On 9 October, Sally Ann and Sounder repeated the survey lines they did for the first IOP.  Survey lines and CTD data is shown beow.  Lots of repeatable frontal structure.

 

What might that frontal structure look like from the surface?  Well it looks like foam scum lines that are filled with algae. The two photos below are from 9 October which had Hs>2 m.   The first photo is looking north at Pt Sal and Lion Rock.  Note the big foam/algae streak (scum line) heading from Pt Sal to the right of Lion Rock.   The scum line can be very dense – even a few inches thick of foam!

Algae scum line coming off of Pt Sal and heading SE indicating the presence of a front where downwelling is occuring.

Close up of massive algae scum line coming off of Pt Sal on 9 October.

 

On IOP2 Day 6, 14 October, we again had 4 vessels doing joint surveys with the APL plane flying IR & visible and helping guide us.  The Sally Ann did a survey box much tighter near the strong bathymetric variations around Pt Sal.    The survey box below started east just offshore and south of Ghost Reef, passed Seal Rock and then Lion Rock, before turning north for a short leg and then offshore again between Pt Sal and Lion/Seal Rocks.

Here are some photos of those features.

A wave breaking at Ghost Reef up close on 15 Oct. The depth goes from 15 m to <4 m very rapidly (Mike Kovatch).

The NPS boat “SandCrab” racing to the south past Ghost reef to recover instruments. They did not stop for tea and biscuits (Mike Kovatch)

Waves breaking on Seal Rock just south of Pt Sal. Drifters recirculated behind this feature (F Feddersen)

All boats passed through many strong frontal features that had more wake, eddy, and recirculation properties than of NLIW.   Notice the repeatable front properties as the Sally Ann drove the box 4 times.

Sun sets on turnaround cruise

The R/V Oceanus offloaded personnel early this morning in Monterey Bay, bringing to a close the ship’s role in the second intensive operating period (IOP). The Oceanus weathered some sizable swells this past week and is currently steaming up to Newport with hopes of dodging another incoming storm in the north. This research vessel never sleeps.

To commemorate the hustle and bustle we have seen aboard these last twelve days, here is a science GIF (the best type of GIF, if you ask me!) from October 6th.

Mooring redeployment at dusk on October 6th aboard the R/V Oceanus

This sequence is from redeploying our second mooring (MS50-T). You can see us standing in a line on the deck of the ship, holding instruments in hand as we wait for the top float to be released overboard.

I have to admit that the feeling of putting those first few moorings back in the water– after an exciting and frenzied 24 hours between recovery and redeployment– was that of pride and relief: pride for how much we had accomplished in a short amount of time, and relief that the instruments were going back into the ocean where they belonged. As engineer Pavan Vutukur said when he saw the mooring returned to the water with numerous of his lab’s GusT instruments attached:

“Now that they’re going back? I feel so much better.”

We look forward to seeing those instruments again at the end of October. But for now, the sun has set on the second IOP aboard the Oceanus.

— Jenessa Duncombe and the R/V Oceanus team

The Kalipi kicks off another week on the water

The Kalipi is back in action starting today. The OSU group recovered the 10-meter temperature string mooring and the ADCP lander this morning. The seas were glassy calm and the instruments were all returned ondeck safely. The recovery could not have gone better. As Jim Lerzcak said when we brought the lander onboard: “There’s nothing like the warm fuzzy feeling when an ADCP comes back pinging.”

The five of us will be running CTD and ADCP surveys for the rest of the week from the Kalipi. Look for us out there, Oceanus, Sounder, and Sally Ann!

— Jenessa Duncombe and the Kalipi team

Jim Lerczak showing excellent

cotter-pin-removal form

Hoisting a lander onboard:

85% winch and 15% muscle

All smiles after a successful recovery

(from left to right: Jack McSweeney,

Dean Henze, Taylor Eaton,

Jim Lerczak)

Ocean color at NASA

NASA has put Pt. Sal at the center of their ocean-color reporting (a coincidence?). Thanks to Kate Adams for pointing out the current regional phytoplankton bloom: It’s on the front page of ocean color today: https://oceancolor.gsfc.nasa.gov/

“On October 4, 2017 the Aqua/MODIS sensor saw some oceanic fall color that is less often noticed than the corresponding land-based colors of deciduous forests. The offshore colors in the above view of western North America are from sunlight reflected by water and phytoplankton.”

Check out these internal waves

Dispatch from the R/V Oceanus

Tow-yo sampling is not the most invigorating of field work. It involves watching a screen and calling out depths every few minutes as the CTD moves up and down in the water column. This continues for hours on end (our October 5th sampling lasted for eight hours straight).

To fight against the inevitable hebetude, we have all adopted our own strategies. Steve likes to make up rhymes. Maddie drinks espresso. Dean watches the live CTD temperature and salinity plots and ponders the oceanographic processes behind them. Personally, I like to save a slice of pie from dinner and eat it very very slowly.

The good news is that the monotony is worth it. The results of our recent tow-yo survey on October 5th captured an internal wave propagating up the shelf, visible in the series of plots below. The plots show temperature over depth along the inner and mid-shelf for four consecutive transects. As you can see in the plots, the internal wave is evident moving along the sharp temperature interface. The wave moves up the shelf before flattening out into a surge as it nears shore. See also how the wave displaces the warm pocket of nearshore water towards the west (best seen by comparing plots 2 and 3). In the last two plots, you can see the next shore-ward propagating internal wave making an appearance.

Something else to note is the seasonal characteristics of the mixed layer. The upper layer is very well mixed and homogeneous in temperature down to about 20 meters. These plots are quite a contrast to the profiles from September, which were stratified throughout the water column and lacked a mixed layer. In this case, the increase in wind must be the culprit. We have certainly been feeling the effects of the windy weather on-board.

We plan to sample more internal waves and other interesting features with the tow-yo in the days ahead. We will also increase our sampling to a continuous 26 hours. We hope a longer record will help us better resolve the waves’ propagation and serve as a valuable addition to the remote sensing efforts and mooring array data. It might also mean that we’ll need more pie.

– Jenessa Duncombe and the R/V Oceanus team

Figures courtesy of Steve Pierce

scripps oceanography uc san diego