From Chief Scientist Ray Schmitt,
Blog Entry: The mother of all tangles...
One of our missions on EN-522 was to rescue and re-anchor one of the
NOAA "Prawler" moorings that had come adrift. The Prawler is a unique
new type of mooring that has a surface float with a jacketed wire rope
suspended beneath it upon which a CTD can travel. The CTD is part of a
package that uses a clever ratcheting mechanism to crawl up the wire as
the wire heaves up and down with the surface waves. Once it gets near
the surface the ratchet is released and the CTD package drops and
collects a profile of temperature and salinity, transmitting the data by
inductive coupling through the wire to the surface pod, where it is
radioed via satellite to the scientists back home.
The wire extends to 700 m depth, where it is connected to synthetic
line. There are two types of line used, the first after the wire is
heavier than water, then that transitions to line that is lighter than
water. Finally, there are glass balls for floatation, an acoustic
release, and anchor. The arrangement of heavy and light synthetic
causes the line to take on a sideways "S" shape in the water, since much
more line is used than the depth of the water. This makes for a
sizable "watch circle" that the buoy will occupy at the ocean surface,
but an "S-tether" mooring means much less stress on all the line than a
taut mooring would have, and the line does not get wrapped around the
anchor.
When we recovered the top portion of the mooring from its drift
100km to the south, it was still working and collecting data and we had
no problem locating it and pulling in the wire. We found no synthetic
at all at the end of the wire, just an empty thimble in the shackle. It
looked like the eye-splice had failed.
Several days later we sent the the acoustic signal for the release
to let go of its hold on the anchor. This allows the very buoyant
hollow glass balls to bring the lower portion of the mooring to the
surface. Waiting for the balls to reach the surface is always a bit of a
tense time in a mooring recovery, balls might have collapsed and there
might not be sufficient buoyancy to bring everything to the surface. We
could tell by acoustic ranging on the release that it was coming up,
but very slowly. It ended up taking three hours, but the bright yellow
hardhats were easy to spot a few hundred meters off the port quarter
when they did surface. We grabbed the balls and started reeling in the
many kilometers of line. The first section of buoyant line came in very
nicely, but we quickly ran into trouble with the heavy line. A lot of
it was muddy, so it had been lying on the seafloor in a big tangle. And
what we brought up was a series of large tangled knots, as you can see
in the photos. It looked to be a hopeless tangle, and prospects did not
look good for redeploying the mooring.
We were particularly interested in finding the bitter end of the
line, to see how it had failed. But because of the large tangle and the
necessity to make several cuts juts to get it aboard, we never found
the expected shorter transitional lines that the design called for.
WHOI mooring maestro Jeff Lord and crewman Paul Rousell worked
diligently over the next few days to untangle the mess. Jeff went over
every inch of the line and re-spliced the larger pieces and re-spooled
them on to the winch. However, since we could not find the expected
termination of the line, we did not know how much of the line we had
left. How a line could part in two places is a mystery, but the most
likely scenario has the line parting somewhere mid-length, then a short
length still attached to the wire but with no tension, was cyclically
whipped around by the vertically heaving wire rope till the eye-splice
parted.
We decided to go ahead with the redeployment; we had brought another
anchor for the purpose. But since we did not know how much line we
had, we had to be flexible in the depth of water we chose for the anchor
site. As the mooring was deployed we had three different people count
the revolutions of the drum and use the minimum and maximum radii to
estimate the line length. The estimates came to about 2600m. It was
deployed with 3400m of the heavy line so we were missing some 800m of
line! These moorings were designed with quite a bit of scope but
clearly we had to choose the shallowest spot available. This we could
do by choosing where to release the anchor, as we trailed over 6
kilometers of line behind us. Fortunately we had a very good SeaBeam
survey of the bottom in the area that we had done last September from
the Knorr. Chris Duncombe-Rea searched for the minimum depth in the
data set and found a nice rise in the seafloor that would still give a
reasonable shape to the array of three moorings. We watched the
echosounder anxiously as we steamed for the spot, and the bottom did
come up smoothly. In fact we got exactly the same depth at the same
spot that the Knorr had measured 6 months previously! We steamed
another 300 meters to allow for anchor fall back and let it go. We
surveyed the anchor by triangulating on three acoustic distances from
nearby sites and hoped for the best.
Fortunately, a few hours later we got word from the folks at NOAA
that the Prawler was working nicely. Its very gratifying when such a
big mess can be straightened out by smart, hardworking people, the
numbers fall into place nicely and a novel contribution to our ocean
observing tools can be put right again!
--Ray Schmitt 4/06/13
SPURS March 2013
Saturday, April 6, 2013
Tuesday, April 2, 2013
Endeavor Update 13-04-02
From Chief Scientist Ray Schmitt,
Cruise Narrative, EN-522
EN-522 got underway at about 10:30 on Friday March 15 from the URI pier in Narragansett. Seas were calm and winds were light at first, but picked up as the day wore on and we got further offshore. Overnight we had winds in excess of 30 knots and the ship slowed and altered course to cope with the seas. Conditions had improved by Saturday evening and we were able to make 10 knots again as we got offshore and entered the Gulf Stream.
The Thermosalinographs were running and a sampling schedule was set up for calibration bottle samples. An additional TSG was set up and fed with a special pump and debubbling system utilizing a long hose dragging across the water. The hose was held about 20' off the starboard side of the ship well forward of the CTD deployment area. When the ship is going faster than a few knots the hose is sampling the upper 10 cm of the water. This system allowed us to sample any near-surface changes in salinity due to diurnal warming or rainfall. It was set up by Julian Schanze and tuned during the transit.
After eight and a half days of steaming we arrived at the SPURS site under much improved conditions. Winds were light and the sun was mostly bright for much of our time on site.
Sunday 3/24
The first order of business was to reset the WHOI mooring. The releases were fired and the balls and line retrieved Sunday morning, 3/24. We did not have to recover the whole mooring, just the synthetic line at depth. There was a concern for chaffing at the eyesplice termination that caused us to do this line change, and indeed we did observe some chaffing. The whole mooring operation proceeded without incident under fine weather conditions. Completing the mooring operation allowed us to clear the decks somewhat and move the small boat to the main deck for easier deployment.
Monday 3/25
We used the small boat to launch two micro-gliders. Seagliders were deployed from the ship. Two WaveGliders were recovered from their holding sites near the WHOI mooring, They were snagged from the small boat then lifted aboard with the knuckle crane. We then started steaming south to retrieve a Seaglider, the Mixed Layer Float and the drifting NOAA mooring (Pico- North).
Tuesday 3/26
This was a day of securing lost assets. Seaglider 189 had run low on battery power and had been parked at the surface for some time. The Mixed Layer Float deployed in September had some ballasting issues but fortunately had not drifted too far afield. The NOAA Pico ?North mooring had broken free about a month earlier and we hoped to collect it and redeploy if possible. All three of these were found and retrieved on Tuesday. The small boat was used each time, in the case of the MLF and the NOAA mooring, it was to secure a means of lifting the gear aboard the ship or bring the gear to the ship, SG189 was retrieved in the small boat. That night we did a south to north U/W CTD section back toward the mooring array.
Wednesday 3/27
We performed microstructure profiling with the VMP near to ASIP and the gliders. Several of us went over the Sarmiento for "International Salinity Summit Talks" and dinner while the Endeavor chased down the remaining WaveGlider. This WaveGlider was steaming its programmed mission but had lost communications, so could not be commanded to its holding site. However, it was easy to find by following its assigned track. Endeavor returned to Sarmiento before sunset to retrieve the three scientists via small boat. Overnight we did CTDs at the corners of the old mooring ?control volume? and UnderWay CTDs between.
Thursday 3/28
At 0800 GMT we fired the release for the NOAA Pico-North mooring to recover the release, glass balls and line in order to be able to redeploy it. It took three hours for the balls to surface, and the initial (buoyant) line was reeled in easily. However the polyester (heavy) line came up all snarled in large tangles. It had clearly been sitting on the bottom, some of it was muddy. We worked hard to untangle it but found that we had to make numerous cuts in the line to get it all aboard. It looks like we would have to re-evaluate the plan to redeploy the mooring, though Jeff may be able to untangle and splice the line back to a usable length. This recovery took much of the day. That evening we deployed a Seaglider and did a CTD calibration cast near it when it dove. We then started a CTD section along 38 W to the south with 1000m stations every 5 nm. The Sarmiento had found a patch of fresh water intruding from the south in its SeaSoar surveys and we were planning ASIP, Glider and VMP work in a suitable fresh intrusion site so this section served in the search for the fresh intrusion.
Friday 3/29
After completing the CTD section we returned to the northwest to retrieve Seagliders 190 and 191 with the small boat. We then steamed toward ASIP for VMP profiling. By this time the micro-gliders were not close to ASIP. We worked on improving VMP profiling by adjusting winch settings and boat speed. VMP?s continued till midnight.
Saturday 3/30
We continued the CTD section along 38 W further to the south overnight. We then steamed to the NOAA Pico-East mooring, launched a small boat to secure a lifting tether and hoisted the buoy up at the stern A-frame using the mooring winch. The old Prawler unit was swapped out for a new unit. Our NOAA colleagues confirmed that it worked later in the day. We then steamed to the WHOI Mooring and Jeff Lord visited the buoy to check meteorological equipment, one system on the buoy seems to be down. We will likely revisit the Buoy later in the cruise once the engineers have diagnosed the problems. We then steamed to recover the two microgliders, Helo and Saul, securing them just before sunset. Plans were made to re-deploy with ASIP on Sunday at a site to the south-south west so a north to south CTD section was done overnight along 38 25' W.
Sunday 3/31/
We stopped the section at 23 50' N and steamed a few miles east to retrieve one of last year?s ARGO floats that had developed a small leak. We then steamed to the ASIP position and deployed Helo and Saul quite near it. We then deployed the VMP first steaming north away from the cluster of instrument then approaching again from the north along a parallel section about 1 km west of their position. This was continued till 2100 (local) then we restarted the CTD section further south along 38 25'W.
Monday 4/1
The CTD section along 38 25'W was continued, reaching 23 10'N. We then steamed north back to the ASIP/Glider site for further VMP profiling. After several hours the Sarmiento steamed into site and the chief scientists discussed plans over VHF. The Gliders were recovered at about 16:30, while Sarmiento recovered ASIP. We then began steaming to the north for a CTD section north along 38 W starting near the NOAA Pico-North mooring site. The NOAA mooring redeploy is planned for tomorrow morning.
Cruise Narrative, EN-522
EN-522 got underway at about 10:30 on Friday March 15 from the URI pier in Narragansett. Seas were calm and winds were light at first, but picked up as the day wore on and we got further offshore. Overnight we had winds in excess of 30 knots and the ship slowed and altered course to cope with the seas. Conditions had improved by Saturday evening and we were able to make 10 knots again as we got offshore and entered the Gulf Stream.
The Thermosalinographs were running and a sampling schedule was set up for calibration bottle samples. An additional TSG was set up and fed with a special pump and debubbling system utilizing a long hose dragging across the water. The hose was held about 20' off the starboard side of the ship well forward of the CTD deployment area. When the ship is going faster than a few knots the hose is sampling the upper 10 cm of the water. This system allowed us to sample any near-surface changes in salinity due to diurnal warming or rainfall. It was set up by Julian Schanze and tuned during the transit.
After eight and a half days of steaming we arrived at the SPURS site under much improved conditions. Winds were light and the sun was mostly bright for much of our time on site.
Sunday 3/24
The first order of business was to reset the WHOI mooring. The releases were fired and the balls and line retrieved Sunday morning, 3/24. We did not have to recover the whole mooring, just the synthetic line at depth. There was a concern for chaffing at the eyesplice termination that caused us to do this line change, and indeed we did observe some chaffing. The whole mooring operation proceeded without incident under fine weather conditions. Completing the mooring operation allowed us to clear the decks somewhat and move the small boat to the main deck for easier deployment.
Monday 3/25
We used the small boat to launch two micro-gliders. Seagliders were deployed from the ship. Two WaveGliders were recovered from their holding sites near the WHOI mooring, They were snagged from the small boat then lifted aboard with the knuckle crane. We then started steaming south to retrieve a Seaglider, the Mixed Layer Float and the drifting NOAA mooring (Pico- North).
Tuesday 3/26
This was a day of securing lost assets. Seaglider 189 had run low on battery power and had been parked at the surface for some time. The Mixed Layer Float deployed in September had some ballasting issues but fortunately had not drifted too far afield. The NOAA Pico ?North mooring had broken free about a month earlier and we hoped to collect it and redeploy if possible. All three of these were found and retrieved on Tuesday. The small boat was used each time, in the case of the MLF and the NOAA mooring, it was to secure a means of lifting the gear aboard the ship or bring the gear to the ship, SG189 was retrieved in the small boat. That night we did a south to north U/W CTD section back toward the mooring array.
Wednesday 3/27
We performed microstructure profiling with the VMP near to ASIP and the gliders. Several of us went over the Sarmiento for "International Salinity Summit Talks" and dinner while the Endeavor chased down the remaining WaveGlider. This WaveGlider was steaming its programmed mission but had lost communications, so could not be commanded to its holding site. However, it was easy to find by following its assigned track. Endeavor returned to Sarmiento before sunset to retrieve the three scientists via small boat. Overnight we did CTDs at the corners of the old mooring ?control volume? and UnderWay CTDs between.
Thursday 3/28
At 0800 GMT we fired the release for the NOAA Pico-North mooring to recover the release, glass balls and line in order to be able to redeploy it. It took three hours for the balls to surface, and the initial (buoyant) line was reeled in easily. However the polyester (heavy) line came up all snarled in large tangles. It had clearly been sitting on the bottom, some of it was muddy. We worked hard to untangle it but found that we had to make numerous cuts in the line to get it all aboard. It looks like we would have to re-evaluate the plan to redeploy the mooring, though Jeff may be able to untangle and splice the line back to a usable length. This recovery took much of the day. That evening we deployed a Seaglider and did a CTD calibration cast near it when it dove. We then started a CTD section along 38 W to the south with 1000m stations every 5 nm. The Sarmiento had found a patch of fresh water intruding from the south in its SeaSoar surveys and we were planning ASIP, Glider and VMP work in a suitable fresh intrusion site so this section served in the search for the fresh intrusion.
Friday 3/29
After completing the CTD section we returned to the northwest to retrieve Seagliders 190 and 191 with the small boat. We then steamed toward ASIP for VMP profiling. By this time the micro-gliders were not close to ASIP. We worked on improving VMP profiling by adjusting winch settings and boat speed. VMP?s continued till midnight.
Saturday 3/30
We continued the CTD section along 38 W further to the south overnight. We then steamed to the NOAA Pico-East mooring, launched a small boat to secure a lifting tether and hoisted the buoy up at the stern A-frame using the mooring winch. The old Prawler unit was swapped out for a new unit. Our NOAA colleagues confirmed that it worked later in the day. We then steamed to the WHOI Mooring and Jeff Lord visited the buoy to check meteorological equipment, one system on the buoy seems to be down. We will likely revisit the Buoy later in the cruise once the engineers have diagnosed the problems. We then steamed to recover the two microgliders, Helo and Saul, securing them just before sunset. Plans were made to re-deploy with ASIP on Sunday at a site to the south-south west so a north to south CTD section was done overnight along 38 25' W.
Sunday 3/31/
We stopped the section at 23 50' N and steamed a few miles east to retrieve one of last year?s ARGO floats that had developed a small leak. We then steamed to the ASIP position and deployed Helo and Saul quite near it. We then deployed the VMP first steaming north away from the cluster of instrument then approaching again from the north along a parallel section about 1 km west of their position. This was continued till 2100 (local) then we restarted the CTD section further south along 38 25'W.
Monday 4/1
The CTD section along 38 25'W was continued, reaching 23 10'N. We then steamed north back to the ASIP/Glider site for further VMP profiling. After several hours the Sarmiento steamed into site and the chief scientists discussed plans over VHF. The Gliders were recovered at about 16:30, while Sarmiento recovered ASIP. We then began steaming to the north for a CTD section north along 38 W starting near the NOAA Pico-North mooring site. The NOAA mooring redeploy is planned for tomorrow morning.
Monday, April 1, 2013
Science Update 01-april-2013
Three nights ago our SeaSoar CTD failed. It
was probably a flooding, the second on this cruise. This is as unfortunate as
it is unusual, and affected two units that had been recently calibrated . We
were on our way towards the southeast corner of the initial SeaSoar survey to
confirm the location of the low salinity feature we encountered there a couple
of days ago. To our surprise the conditions at the surface had changed quite a
bit. TSG and ADCP showed a very different picture than only 4 days ago. What
seemed like a broad low salinity “blob” now was only a thin elongated filament.
We spent the night trying to figure out
where this feature had gone. It was, after all close to 100 m deep, thus represents
quite an amount of freshwater. The rapid changes are once again confirming the
high variability in this ‘quiescent blob’ (as one might call it looking at mean
climatologies), affirming the need to study it in detail and on various time
and space scales.
The experience from that night led to the
decision to deploy all our drifter assets now, to give time for a repair of the
SeaSoar and furthermore to monitor the rapid changes within the SPURS box. As
an additional bonus we are able to repeat most of the SeaSoar radiator survey
with the TSG while we deploy the drifters and ASIP.
It turned out that a low salinity feature
is now seen in the central eastern part of the SPURS box. Good drifter coverage
by the end of today will enable us to plan where we should focus on a
freshwater experiment, concentrating ASIP and additional drifters from the
ENDEAVOR in a fresh patch to contrast the experiments within the saltiest
patches. During that experiment in the last days of the cruise, the Spanish
vessel will conduct another SeaSoar survey to provide the large scale context
and might be able to examine the evolution of such an intrusion by following it
from the ‘fresh’ frontal zone towards the origin, which might be to the south.
Sarmiento Update 13-03-31
From Chief Scientist Jordi Font,
Sunday report:
- New ASIP deployment at 23 52.5', 38 24.6'. Will be recovered after 34-35 h
- Continued drifters deployment. All Pacificgyre released, now releasing ICM units
- Picked up three ICM+LOCEAN prototype drifters released the previous day
Plan for Monday:
- Finish drifters deployment in the 75 nm x 75 nm central box
- 7 CTDs along 38 41.4' spaced 15 nm
- Recovery of ASIP and Apex
- Decide new SeaSoar + floats sampling strategy. Probably targeting again the SE low salinity area
We placed one drifter (#114994) in the same point where we had deployed the first one on the 27th (#114956) and that apparently has never emitted.
Concerning multiple deployments, we released a triplet near to WHOI mooring, another one outside (SE) from the central box where we had observed the maximum S gradient, and a third one in the NE corner of the box.
Now we have a certain shortage of drifters (CTDs and drogues being used in experimental short-term deployments) and will just fill the 36 points in the box without more triplets. We still will have four drifters (one with CTD at 5, 10 and 50 cm) for work in the low salinity area we are targeting for the last part of the cruise.
Regards,
Jordi
Sunday report:
- New ASIP deployment at 23 52.5', 38 24.6'. Will be recovered after 34-35 h
- Continued drifters deployment. All Pacificgyre released, now releasing ICM units
- Picked up three ICM+LOCEAN prototype drifters released the previous day
Plan for Monday:
- Finish drifters deployment in the 75 nm x 75 nm central box
- 7 CTDs along 38 41.4' spaced 15 nm
- Recovery of ASIP and Apex
- Decide new SeaSoar + floats sampling strategy. Probably targeting again the SE low salinity area
We placed one drifter (#114994) in the same point where we had deployed the first one on the 27th (#114956) and that apparently has never emitted.
Concerning multiple deployments, we released a triplet near to WHOI mooring, another one outside (SE) from the central box where we had observed the maximum S gradient, and a third one in the NE corner of the box.
Now we have a certain shortage of drifters (CTDs and drogues being used in experimental short-term deployments) and will just fill the 36 points in the box without more triplets. We still will have four drifters (one with CTD at 5, 10 and 50 cm) for work in the low salinity area we are targeting for the last part of the cruise.
Regards,
Jordi
Sunday, March 31, 2013
Nights on a research vessel
A research cruise is a twenty-four hour operation. Some instruments, like the SeaSoar, need constant supervision. This means the operators have to work in shifts around the clock. Other measurements have to be taken at a specific time of the day, and sometimes the schedule changes quickly and people need to arrange a spontaneous recovery of an instrument.
Night on deck of the SARMIENTO |
Kintxo and Miquel check the APEX float before the deployment |
The nights on the vessel are impressive.
The sky is usually clear and there is nothing around us that emits light, except
for the ship. The perfect opportunity to sit on deck and watch the moon and
stars while the ship gently rocks on the waves.Yesterday we had full moon and the views of the moon are simply fascinating at night.
The moon light causes a halo in the night sky |
Thursday, March 28, 2013
Visitors on the open ocean
The ENDEAVOR |
To meet other ships up close is rare on the
open ocean. This made the rendezvous between the American ENDEAVOR and the
Spanish SARMIENTO a very interesting change of the daily routine. Since SPURS
is an international cooperation, the chief scientist Ray Schmitt, Chris
Duncombe-Rae and Julian Schanze climbed in the zodiac and navigated to the
SARMIENTO under the eyes of scientists and crew on deck, who were watching the
ENDEAVOR up close while the visitors were approaching.
Watching the visitors |
The guests are all SPURS veterans from the
R/V KNORR cruise in September 2012 and everybody was eager to share initial
results and discuss the further planning.
But first the guests were shown around the
spacious SARMIENTO and introduced to the captain and officers. Over dinner and
coffee the further approach for the mission was discussed.
While the ENDEAVOR will be busy with
recovering and maintaining instruments until the weekend, we will start another
SeaSoar deployment in hope to find a fresh intrusion like the one we saw on the
Southern end of the first SeaSoar sections. This will provide an opportunity to
deploy instruments from both ships and map the region around the feature.
Helping us to understand how freshwater is carried into the region and
eventually enhanced in salinity again, due to exchange of moisture to the
atmosphere.
Sarmiento Update 13-03-27
From Chief Scientist Jordi Font:
Last night we started releasing Luca's drifters (#114956, 114955, 114905, 114906, and a triplet 114814-114952-114911). We deployed again ASIP near to WHOI mooring and are now steaming south towing SeaSoar according to the strategy agreed yesterday in the joint Sarmiento-Endeavor meeting. Find attached a figure with release positions and planned SeaSoar track.
The rest of drifters will be released in the forthcoming days, using the time intervals between ASIP deployments.
On Wednesday we also deployed an Apex float in 24.702 -38.146 to perform shallow cycles (200 m). It has not been notified to the Argo system as we intend to use it in short deployments. We will send its positions in order to be included in the overall SPURS positioning data set (even it only surfaces for a few minutes every 4 h). We plan to pick it up on Saturday, after ASIP for a joint deployment on Sunday in the low salinity area in the SE that we are now going to map.
You can see many pictures in our ICM blog http://www.icm.csic.es/icmdivulga/ca/campana-spurs-03.htm (translated version)
Regards,
Jordi
Last night we started releasing Luca's drifters (#114956, 114955, 114905, 114906, and a triplet 114814-114952-114911). We deployed again ASIP near to WHOI mooring and are now steaming south towing SeaSoar according to the strategy agreed yesterday in the joint Sarmiento-Endeavor meeting. Find attached a figure with release positions and planned SeaSoar track.
The rest of drifters will be released in the forthcoming days, using the time intervals between ASIP deployments.
On Wednesday we also deployed an Apex float in 24.702 -38.146 to perform shallow cycles (200 m). It has not been notified to the Argo system as we intend to use it in short deployments. We will send its positions in order to be included in the overall SPURS positioning data set (even it only surfaces for a few minutes every 4 h). We plan to pick it up on Saturday, after ASIP for a joint deployment on Sunday in the low salinity area in the SE that we are now going to map.
You can see many pictures in our ICM blog http://www.icm.csic.es/icmdivulga/ca/campana-spurs-03.htm (translated version)
Regards,
Jordi
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