GoM Hydrate, Daily Log

Steven Constable

On this web page I will be posting daily updates on the progress of our cruise on the R.V. Roger Revelle in the Gulf of Mexico. The object of this project is to map seafloor gas hydrate at three or four locations in the GoM, with an add-on for student John Blum which will involve a detailed bathymetric survey of suspected submarine landslide.


25/10/2008: We tied up today at 3.00 pm. This is my last log entry. And I'll keep it short.

If you've enyoyed reading these entries drop me a line at sconstable@ucsd.edu.


23-24/10/2008: Didn't get a log posted last night 'cos things got rather hectic. The rest of the SUESI tows went well, and we even had time to add a tenth line to the survey, which nearly ended up being a mistake. Instead of finishing tows an hour or two early, we finished an hour or two late, but I figured my crack deck teams would be able to make that sort of time up easily on the instrument recoveries. I had budgeted 45 minutes a recovery, but we've been doing better than that and the dense grid of instruments makes things even easier. Well (I use that word a lot), a front came through shortly after recoveries started at 4:30 pm and made things a bit more interesting on deck, but most importantly made the noisy acoustics even noisier. We started OK, but soon were not able to see instruments unless we were very close, which made keeping the pace of recoveries very difficult. It takes at least an hour to recover an instrument from scratch (5-10 minutes to release, 45 minutes to rise (900 m water here), and about 10-20 minutes to get them on the ship), so the idea is that you release the next instrument before you recover the last, `popping' them 30-45 minutes apart. But if you can't see the next instrument on the acoustics that falls apart, and it did. I had horrible visions of running over time (we were due to leave station at 08:00), getting in too late to clear customs and immigration, and having a ship-load of sailors and scientists who had been promised a party stuck on a dry ship Saturday night.

But, crack teams are not called crack teams for nothing and we pushed things hard, sometimes popping instruments at 20 minute intervals when we could see them. I went to bed around 2 am with a scheme in play and was woken around 8:15 am by the characteristic pitching of a ship in full motion. So I went back to sleep.

We are now on our way home after a cruise that has set many records for our group. 94 seafloor deployments and recoveries, over 100 hours of transmitter operation on 18 tow lines, 92 data sets collected (96 if you include Vulcan), all in a little over 12 days on station. The vast majority of the data is of superb quality. Always important, nobody came close to getting hurt (a small finger cut was the extent of it). The generally excellent weather (give or take last night) certainly helped, but the fine work from all of the deck, engine, and science departments was the key factor.

22/10/2008: Well, I was setting myself up yesterday, but in fact life is still good. We are halfway through the seventh SUESI tow line of nine planned over this area. Barracudas have been in and out of the water but are mostly working. We are on track to finish towing on time at noon tomorrow and may even get an extra tow line in before we have to stop.

The excitement tonight was provided by two flashing strobe lights that looked from afar very much like our instruments. It seemed improbable that we'd started to have instruments break loose from the bottom after 70 successful deployments, but stranger things have happened. We can't maneuver with 1000 m of wire and other assorted kit hanging from the back of the ship, but we managed to pass close enough to convince ourselves that they were not ours. Fisherman's buoys, probably. We'll find out tomorrow when we start to pull everything back.

21/10/2008: Arrived on station at MC 118 at 8:35 am and had our first instrument in the water at about 8:36. The night crew (midnight to midday) had been giving the day crew (midday to midnight) a hard time about being too slow at deployments. To prove the point the night crew had half the 24 instruments in the water by noon. The day crew were not having any of this. They had the last instrument on the seafloor by 3:55 pm. 24 instrument deployments in 7.5 hours is another record (to go with 8 instuments in the water at once). This rivalry is actually quite helpful - we are trying to squeeze every last hour out of the system to get everything done in the remaining time.

We navigated the seafloor instruments by driving backwards and forwards while ranging on them, and started deploying barracudas, vulcan, and SUESI at 7:15 pm. We have got this down to an art as well, and had SUESI submerged by 9:15. Unfortunately, we had allocated our usual 6 mile/4 hour run-in, so now we are steaming slowly to the instrument array. Of course, now we are so far ahead of things, the ship's speed is a nice slow 1.3 knots. Never mind - THE BARRACUDAS ARE WORKING! We swapped out the surface transponders, tweaked the angles of all the transducer heads, changed one of the frequencies, and now it's all working as planned. We are getting real-time updates on the transmitter position, 800 meters below the ship and 400 meters behind. And we've booked a place for the end of cruise party. Life is good.

20/10/2008: Instrument recoveries finished around 02:00 in the morning and we had a short 4-hour transit to John Blum's multibeam survey site. John is looking for a suspected landslide that may be the cause of a magnitude 5.3 earthquake recorded February 10th 2006. He is using high resolution echo-sounding to see if he can find any characteristic features on the seafloor, and will later try to compare his new bathymetry map with older ones.

Multibeam will finish around 10.00 pm tonight and then we steam to our final CSEM survey at Mississippi Canyon. We've just discovered that we have 97 anchors instead of the 90 we thought we had, so we are going to try to squeeze a couple more deployments in (24 instead of 20).

19/10/2008: The second tow on Green Canyon went just fine and we had SUESI back on deck by breakfast or so. Instrument recoveries are going kinda slow, mostly because we had a problem with the crane we were using to pick the instruments out of the water. We had replaced the wire rope on the crane with nylon line to make it easier to hook into instruments, but we managed to get the rope jammed in the cheeks of the sheave. It's tricky when you first hook into an instrument that is moving up and down several feet in the swell.

Fortunately, there are 3 cranes on the back deck, so we can keep going - the biggest mistake was thinking that it would be quick and easy to get the line out, so we didn't immediately move to another one. Shouldn't complain about the speed, since getting them back is the big thing, but we're down to counting hours back from our 'drop dead' time of 08:00 on the 24th, when we have to leave station to get to Tampa at the appointed time.

18/10/2008: By 9.00 am this morning we had finished deploying 20 receivers and by just after lunch had navigated them in. We put SUESI in the water mid-afternoon and are now just starting our second tow. The wind is a bit brisk, which is causing some struggle to keep the ship on the right heading and the slow (1.5 knot) speeds we like to transmit at. We are still fighting to get the barracuda navigation system working. Some hint that it will function but with the higher towing speeds SUESI is several kilometers behind the ship and out of range. It shouldn't be, but clearly we need to make some improvements to the system. Our next and last survey is in shallower water, so we will give it a last try there.

Even though we're a long way offsore we've been getting a number of birds around the ship and even insects (Chris was bitten by a mosquito!). The aforesaid brisk wind is coming from the north, so maybe they are being blown from land. Weather has cooled down as well, which makes working on deck much more pleasant.

Nothing much to report, really. Boring is good in this business.

17/10/2008: All 20 instruments were recovered at Walker Ridge and now we have just arrived at Green Canyon 955 and dropped our first instrument over the side. There is a tension-leg platform on this block, lit up like a Christmas tree. We had been expecting this and had moved our survey lines to avoid it and its array of seafloor anchors.

Earlier today we opened up the pressure case for SUESI's acoustics and discovered a loose connection, which turned out to be the problem with yesterday's towing. We jigged a retainer for it and with any luck we should have the new barracuda navigation system up and running on this survey.

Weather is still good, the food is still good. Now if only this were a French vessel...

16/10/2008: Finished two tow lines through the Walker Ridge array with no problems other than that SUESI's acoustic system doesn't seem to be working properly, so we couldn't use the barracuda navigation scheme. This is a minor problem that we will debug tomorrow. Spent a few hours after dinner doing acoustic navigation of the receiver instruments and now (23:20 local) we are about to recover the 20 instruments we have on the seafloor.

Started processing various bits of the large (26 Gbyte) data set we collected over Alaminos Canyon. The signal to noise ratios are the best I have seen from our equipment (or, dare I say, anyone else's?).

15/10/2008: Arrived on station at Walker Ridge around 10:00 am and started deploying 20 seafloor OBEM instruments in two lines. All instruments were in by about 7:00 pm - we took some time off for lunch and our weekly fire and boat drill. Today we had simulated pirate attack (crew) and video of donning survival suits (science party). Like all these training videos, it showed people abandoning ship in beautifully calm weather.

At 9:30 pm we started putting our antennas and stuff in the water and by 11:30 we had SUESI in and transmitting. We had a short failure of the winch control system, but we had only just put out 500 m of wire and we were ahead of our 4-hour budget for getting SUESI in, so no harm was done. By 01:45 am we were flying 80 m above the seafloor on the approach to our first tow line. In a word, routine.

14/10/2008: Instrument recoveries continued until 7:00 pm this evening. We recovered all 30 instruments, although the clockwork mentioned in yesterday's posting broke down just after midnight. Because it takes nearly two and a half hours for instruments to float up from the seafloor 2,700 m away, we release instruments at about 40 minute intervals, which is easily enough time for the ship to maneuver and for our crack teams to bring the instrument on deck. However, we had one instrument that didn't release on repeated primary commands, so we (well, I) sent some secondary release commands. This worked, but the delay resulted in two instruments coming up at once, and we ended up with 5 instruments in the water column instead of 4. No real problem - the weather was good. However, 2.5 hours later our nifty little recovery buoys started reporting multiple instruments on the surface. Five, in fact. With strobe lights flashing all around and our instrument tracking box beeping repeatedly it was quite a circus. What had happened was that a quirk of our acoustic releases meant that three other instruments shared the same secondary commands, and because our array was only 5 km square they all heard the release call. Eight instruments in the water at once is a personal record I hope will not be broken.

A total of 29 instruments recovered data (the A/D converter on one locked up), and of these we have one noisy channel out of a total of 151. Not too shabby! We are currently in transit to our next survey site at Walker Ridge, with an ETA of 9:45 am tomorrow.

13/10/2008: These are the days we live for. SUESI#1 performed flawlessly as we towed 4 lines through our array of 30 instruments. By just after noon SUESI was back on deck and we pulled in the barracudas and vulcan/antenna array. Vulcan data look great, and the various depth, pitch, and roll sensors worked properly. At 15:00 we started instrument recoveries, which are going like clockwork in spite of noisy ship's acoustics. Every data set we have looked at is gorgeous - many months of pre-cruise checkout and testing are paying off today. Life is good (although a little more sleep would be nice).

11-12/10/2008: Well, we've just come through a rough patch. Yesterday (the 11th) started out really well with the deployments done by just before lunch and navigation to find accurate locations finished around 3.00 pm. We then started prepping and deploying the various stuff we use for deeptow EM transmission; surface-towed navigation transponders ("barracudas"), 3-axis E-field recorder towed behind the transmitter ("vulcan"), and our just recently built backup transmitter, SUESI#2. Took about 4 hours to get SUESI in the water and towing. We had SUESI down to about 1400 m when it died, fairly gracefully, but dead nevertheless.

We hauled it in and landed it on deck, where it worked briefly for a minute and then died again. We think the problem is breakdown in a custom built 2000V/110V transformer which supplies the power to operate the control and navigation electronics. We've had quality control problems with this part in the past.

We set SUESI#2 aside and started to bring SUESI#1 over to the A frame, when (a) the crane started leaking hydraulic fluid and (b) we realized that the starboard barracuda had tangled with the vulcan array streaming behind SUESI, which was now on the surface. While the engineers worked on the crane we pulled barracuda and the array back in. By this time the crane was working well enough to get SUESI#1 spotted for deployment. We rigged everything up, and started tests.

Everything was fine except the CTD gauge was not working, even though this unit had been working for the last several experiments. We were now well into the night and not feeling too chirpy, but we started diagnostic tests and finally traced the problem to a mis-wired cable. We re-made the cable and deployed sometime in the wee small hours. We reached our target depth of 100 m above the seafloor about breakfast time and towed the main line for this first survey absolutely fine, 200 Amps and barely ticking over. We have just started turning onto the second line (16:00 local).

So, apart from a little loss of time, which we will have made up if the team recovers instruments as fast as they deployed them, and a sleepless night of hair-pulling, we are doing more than just fine. Perhaps it was a little audacious to put a brand new transmitter into the water as our main instrument, but we nearly succeeded. Breeze is up which means we've got some wire angles, but weather is still wonderful by any measure. And the food is good, as always on this vessel.

10/10/2008: Clocks turned back an hour last night. A lazy morning during the finish of the transit and then started deploying instruments at 16:30 local. We had a rocky start when we watched the first instrument sink using our acoustics - lots of noise on the system. This would be OK for deployments but navigating and perhaps recovering the instruments would be tough. To make sure the problem wasn't in our home-made acoustic system we went to use our brand new (delivered just days before the start of the cruise) Benthos digital navigation system and discovered that it had fried itself in the night. We pulled out our ORE/Edgetech navigation system and verified that the problem was with the hull transducer. Fortunately the ship has a second 12 kHz 'ducer which we switched to and everything started working (except the fried Benthos). We continued deploying instruments and meanwhile borrowed the Benthos navigation system from our backup deeptowed transmitter and made that work in the lab with some creative cabling.

As of midnight we had 12 instruments over the side. Once they got going the noon to midnight crew was deploying instruments every 30 minutes (we budgeted 45-60 minutes), so we will need to re-tool tomorrow's shedule.

9/10/2008: Today we checked and started up all 30 seafloor data loggers for deployment tomorrow. We get on station at around dinner time (always seems to work that way). We checked and debugged a couple more instrument systems associated with the transmitter, and as of around midnight we have every last system tested out OK, which is a nice place to be. Weather is good, food is good, and we are ready to start work.

8/10/2008: Our trusty student contingent toiled today in the hot sun stringing antennae with electrodes, while the trusty chief scientist toiled in an air-conditioned laboratory weeding out a bad GPS clock, doing some final tests on SUESI, and making some recalcitrant LabView software work. Making good time in slight seas, and expect to be on station the afternoon of the 10th.

7/10/2008: Final beer was good, although for most people it was sangria (at a Cuban restaurant). Spent the day tying everything down and testing a last couple of systems. Held science and safety meeting and distributed cruise T-shirts. Pushed off on schedule at 16:00 heading south with good weather, although this heading is not so great for the HighSeasNet. Students are practicing ping-pong Revelle Rules (bounce off any surface except the floor is fair game). We will have a couple of days transit to get our sea legs and prepare the instruments.

6/10/2008: We terminated the 0.680" coaxial deeptow cable and load tested it to 7,000 lbs. We then switched on our deeptow power supply and tested the high voltage systems. Finally, we plugged in SUESI, our deeptow transmitter, and bought it up to operating voltage and made sure it was 'talking'. All seems well with SUESI, which is good. We assembled some other stuff and tested critical equipment such as the acoustic systems. At the end of the day all the important gear seems to be working. The rest of the science party has started to come aboard and we should have a full compliment by tonight. We're off to have a final beer.

5/10/2008: The advance party of techncians led by Jacques Lemire reports that weather is hot and humid but that all equipment was loaded on the vessel as of last night. Karen, John, Arnie, and Steve fly out to Fort Lauderdale to join the vessel.