Since the first Intensive Operations Period (IOP 1) in September/2017, results from the different groups have been coming together to reveal a complicated plot around Pt. Sal, with lots of topographic wakes, recirculation south of the point, ridiculously sharp fronts and some really aggressive high-frequency internal waves.
Between about noon on the 12th until 9 am on the 13th, we tagged along the other vessels, repeating an L-shaped track in between the Sally Ride and the Oceanus. The collective goal of our Inner Shelf Armada was to observe the flow around the cape and try to understand, among other things, how vorticity is produced by the separating tidal flow and how a background, subtidal along-shelf flow might influence this process.
We crossed what looks like some high-frequency internal wave packets, visible in temperature, velocity and acoustic backscatter. A very sharp front (an internal bore?) with ~2 C change across just two neighboring uCTD profiles was encountered next, with a step-like signature also in the deep chlorophyll maximum and ADCP backscatter. There was a persistent, generally southward larger-scale flow for the entire survey, which lasted for almost a complete tidal cycle.
We had business in the Oceano Array and had to leave early on the second day of surveying, but hopefully by stitching the measurements above together with those from the other 5 vessels (see here, here, here and here) we will learn something about the phenomenology of sharp fronts, headland eddies and incoming high-frequency internal waves around Pt. Sal.
We have recovered all of our (SIO, Feddersen) instruments, and the fun of sorting out and QCing the data has begun, however, I thought I’d share a sweet tale of loss and love. We were fortunate to only leave 2 instruments at Pt Sal, drifter 23 and 24, although I do believe their fate may have always been intertwined. Their tale begins during experiment preparation during final drifter assembly, when drifters were being labeled with a sharpie: 1… 27 – then 23 and 24 were shipped to Pt Sal, right next to each other in a large box. During IOP-1, both 23 and 24 rose to the occasion and provided excellent data from which internal waves, fronts, and surface waves were observed. However, on the final day of IOP-1, Sept. 17, drifter 23 (red in the figure) decided he/she wasn’t long for this world and sacrificed itself (for science, I presume) on the rocks, either that or that the point (0,0) in Pt Sal (x,y) is some sort of worm hole? (actually, we checked some mooring lines, which were kelp free! delaying recovery of 23). Regardless, we had finally lost a drifter, much to everyones dismay (delight?).
Now drifter 24 was sad, however, he/she performed admirably throughout IOP-2 collecting much data. On the final day of IOP-2 (Oct. 14), about 1 month after losing drifter 23, 24 decided enough was enough and attempted to reunite with 23. Upon release at 8:05, 24 went directly shoreward (green in figure), hitting the surfzone at 12:39. Realizing that 23 was 1 km to the south, 24 stumbled down the beach for 4 hours, getting about 200 m from 23’s final resting place. At this point, after stumbling down the beach for 4 hours (a difficult task for an old drifter from the 80s), 24 needed a rest. After a long 24 hour nap, drifter 24 made tje final push south toward 23, coming to rest about 100 m from his partner in science. Although we mourn the loss of these two drifters, we are happy they are once again together enjoying their retirement on a beautiful coastline. (in the figure, contours are at 2.5 m intervals, and the 20 m contour is thick)
The IOP1 asset visualization now includes 3 ships, 3 boats, 2 sets of drifters and x-band radar images! Thanks to Falk Feddersen for hosting the full video of IOP1!
On 15 September the UNOLS vessel trifecta encountered mingling fronts and internal wave packets headed onshore during Oceano surveys. Two-hours of near-surface temperature data trail each vessel. The tightly-packed moorings, soon to be recovered, were in the middle of it all. Good luck to the mooring recovery teams!
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 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
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,
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.”
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
SIO drifters are ready to roll. On our way to Pismo, we successfully retrieved the IOP1 beached drifter from Vandenberg AFB. Thank you to the staff for their assistance!
26 charged GPS units, 26 bundles of CODE drifters, 1 ecstatic Matt Spydell.
Data are not the only things our instruments have brought back to the surface. Several sea critters have become quite attached to our landers. In one case, a tan spotted sea anemone had made a home on the lander’s bottom shaft. Marnie gently evicted the critter overboard.
Another lander brought up three small brown spotted octopuses, which promptly skittered off the tripod as soon as it hit the deck (see two videos here and here). The little guys are surprisingly agile, even with their eyes closed. You can hear Sarah as she holds one of the octopuses in her hands saying, “it’s so sticky!”. We helped them jump ship after some oohs and ahhs.
One of the octopuses, mid-escape. Make sure to you don’t miss our two videos (links above in main text).
As the second IOP begins, we thought we’d share a Song and Dance from the first IOP. Alex and Annika put together a wonderful radar movie of the Oceanus and Kalipi doing their sampling dance around the Oceano array.
(it seems that in order to hear the sound you have to try YouTube Research Vessel Waltz)
We recovered our deepest mooring (MS100-T) from 100 meters first thing on Wednesday morning. The data has now been downloaded and we have two plots to share!
The figures below show temperature contours plotted over depth for several hours selected from two separate days. For those unfamiliar with the MS100-T mooring structure, the line has 26 thermisters spread over about 100 meters and have been deployed since the beginning of September.
Plotting temperature over several hours, we can see vertical oscillations of temperature on short time scales. In these plots, the vertical displacement of isotherms is around ~20-30 m at the onset of the wave and the wave period is approximately ~15 minutes. We believe these vertical displacements are caused by solitons propagating by the mooring. The data sequence shows many of these wave packets in the time record. We selected these time sequences to serve as an example.
We look forward to giving this a closer look in the coming months. For now, we have the data (high-fives all around!) and have since redeployed MS100-T successfully.
– Jenessa Duncombe and the R/V Oceanus team
The crew on the R/V Oceanus left port today from San Francisco under a fortuitous blue sky. We are headed south to Point Sal and expect to arrive in the morning on Thursday. We plan to recover and re-deploy up to 8 moorings and 9 landers over the next five days, as well as continue surveys with the towed Mini-bat/Acrobat (fingers crossed that the kelp forests stay out of our way this time). We have a new instrument as well— a bow chain equipped with thermistors and two GusT’s (pressure readers for depth and turbulence).
Our departure marks the beginning of turnarounds for the long-term moorings and we are excited to get our hands on the data. We do not know what we will find when we make it to the first station tomorrow. Has our mooring “walked” away from its original location? Has any fishing activity inadvertently interacted with our surface buoy? Or is our mooring and its all parts bobbing where we left it last, instruments dutifully recording data?
We hope the last option, but we are prepared for whatever we find. We have fresh batteries and all hands on deck for the recoveries.
Speaking of the team, we have some new faces aboard. The group hails from Oregon State University, Scripps Institution of Oceanography, and the University of Miami. We have five research scientists, two graduate students, two technicians, one postdoc, one engineer, and lastly, one volunteer scientist/journalist (that’s me!). We also feel grateful for our MarTech and Oceanus crew.
Here are a few photos of our time on land, as well of us exiting the bay under the illustrious Golden Gate bridge.
Stay tuned to hear about mooring and landing recoveries.
— Jenessa Duncombe and the R/V Oceanus team
Katherine Pogue (2nd Mate)
SIO Melville lab had our last day of flying the MASS system yesterday. Again we experienced clear skies and windy conditions which provided good signal for our sensor suite. We flew an additional calibration flight after the science flight to wrap things up and spent the day today backing up data and packing up to head home after a successful campaign.
Oceanus finished 24-hours BATing on the Oceano array bounding box. We can see both the large-scale wind-driven response and the NLIWs coming in (see plot below). The storm knocked some kelp free which we managed to catch on the BAT. No harm, no foul.
We were happy to get the BAT back on board and head north. Here’s an ecstatic Johannes Becherer with the GusT sensors on the front of the BAT. The dolphins said hello and sent us on our way north. Heading north, we had a 30-knot head wind and big seas to pound in to.
In the morning, the Golden Gate bridge emerged from the fog as we approached San Francisco. Two more whale sightings in the main channel and by Alcatrez. We scooted past the Financial District, a docked 4000-person cruise ship, AT&T park (The Giants don’t play until tomorrow night) and under the Bay Bridge before reaching our destination.
A great cruise with tons of data collected. We’re looking forward to getting back out again in a couple of weeks.
—Jack Barth and team R/V Oceanus
Our radar at Pt Purisma now has a real time site. Both sites can now be accessed from one link:
Hopefully this is of some use as work gets done further to the south.
The Inner Shelf armada is conducting synchronized along shelf lines off Oceano. Here’s a shot of R/Vs Kalipi and Sounder inshore of Oceanus. They were soon joined by Sally Ann shoreward of Sounder. On the offshore side was Sally Ride. Oceanus’ radar shows the 5 vessels all in a row headed north. The ADCP from Oceanus shows some nice upwelling, with southward flow at both depths and offshore at the surface with onshore at depth. Anyone see eddies in those plots? Thanks to Steve Pierce for the ADCP plots. And thank you V. Walfrid Ekman for the wind-driven flows. Oceanus successfully slalomed through some SWIFT and SIO drifters as they were transported offshore by the Ekman transport. The final shot is of our intrepid Oceanus science team, all 8 of us doing 12-hour shifts of 4 each.
From left to right: Raelynn Heinitz (OSU undergrad, Env. Sci), Mei Sato (OSU postdoc, bioacoustics), Marnie Jo Zirbel (OSU faculty research assistant), Jacqueline (Jack) McSweeney (sitting, OSU postdoc), Jack Barth (OSU), Lisa Nyman (UMiami grad student, marine Doppler radar), Johannes Becherer (OSU postdoc, microstructure) and Steve Pierce (OSU research associate).
Here’s a quick work up of the SWIFT drifts around Pt Sal from the previous few days. The drifts are all southwards (releases are at the northernmost points for each track), and the color scale is the log10 of the TKE dissipation rate averaged over the upper 5 m. Looks like there is a region of high dissipation were the flow separates around the headland and changes direction.
What a difference a day makes. Here’s a photo of a CTD launch on Oceanus this morning (9/15) giving data as we pass through these internal waves visible on the echosounder
The vertical profiles show two groupings, as the internal waves heave the thermocline up and down.
With some clever changes in the plotting scale, you can make fun patterns like this 🙂
This afternoon the winds picked up to over 30 knots and the ocean started looking like the California Current is supposed to look!
We’re presently sampling side-by-side with the Sally Ride on alongshore legs between the Oceano array moorings, mapping out the vorticity field and waiting for the non-linear bore arrival. We’ll measure the velocity and density fields as the ocean gets a shove from these strong winds.
—Jack Barth and the R/V Oceanus team
Here’s a quick plot from one of Sounder’s laps around the inshore box today (14 Sep 2017). The first leg goes along the 20 m isobath from the NW corner to the southwest corner. The upper 10 m of water is headed onshore (red) at ~20 cm/s, and the lower 10 m of water is headed offshore at ~ 20 cm/s. Classic cross-shore exchange? You be the judge. More puzzling is the lack of exchange (or much flow at all, green being ~0 cm/s) along the 10 m isobath….