Friday, November 6, 2009

Passing the baton

That elusive pot of gold… Tradition has it that all cruises end with a sunset. But, just like I have kept to a promise I made myself at the start of the cruise (no matter how boring the blog is, do NOT start writing about what you had to eat). I’ve decided to skip the sunset instead and end with something I had never before seen at sea – a perfect Rainbow. This was a photo we took while riding in very rough and rocky weather back to Grand Cayman at the end of Leg 1 and came to mind today when doing exactly the same at the end of Leg 2. We were sailing right toward it as the sun went down and night fell so I like to think we passed right through its archway.

Position at 13h00 EDT – Approaching Grand Cayman
Lat: 19° 09’N Long: 081° 29’W
Water depth: <2000m

So we are on our way home. Soon after I posted my last blog yesterday the weather turned against us and rose above 20 knots where it has stayed ever since. Indeed, Steve and I even saw gusts over 40 knots at our last CTD station when we got up around 2am to do that final shift. Needless to say that meant the chance of a final Nereus dive to our vent site today never happened. Even the idea of using our small grab became a non-issue because of safety. Actually, that was probably a good thing.

When I thought of that idea last afternoon it was as a chief scientist for this particular project, wanting to get the best possible samples for my various colleagues aboard ship. But then there is the bigger picture:– working in the deep ocean, this project included, is an international collaboration that isn’t ever finished with a single cruise. Considering that what we had found at the bottom of the Mid Cayman Rise may be a quite unique habitat, what might have been more irresponsible than lowering a sampling system in amongst it, blind? Far better to wait until circumstances (e.g. funded research projects, favorable weather) will allow us (as in the collective “us” of the international research community) to do the job properly.

This is what various programs that I have been involved with in the past decade - including the Census of Marine Life and InterRidge, both of which have been very supportive of our work – strive to achieve. So while it would have been wonderful to achieve everything we hoped for in less than 4 weeks on station here, in this first program, what we have already done is prove (a) that there is actually hydrothermal activity present and waiting to be investiagted and (b) localized key target areas from the blank canvas we started with (2000 sq km) to some very precise targets on the seabed. We’ve also proven that – on the days that the weather allows – the technology now exists to send our new Nereus robot vehicle to great depths and observe the seafloor from a much smaller research ship than had ever previously been possible. We think that must already be a world record in its own right.

Of course, that does still leave some major research questions unanswered. From the seawater samples we collected yesterday we will be able to make quite accurate predictions of the types of hydrothermal venting that wait be visited on the seafloor – but nothing about their biology. Happily, it probably won’t be long before those questions, too, get answered. Informed by what we have learned here, two new research cruises will be returning to the same area in 2010, the first in just a few months from now. This time next year, Jon Copley – who will be taking over from me as InterRidge Co-Chair on Jan 1st 2010– will be leading a cruise from the National Oceanography Center, Southampton to dive to the MCR using Isis – the sister vehicle to WHOI’s better known ROV Jason. But before that, Doug Connelly (you’ll remember him from Leg 1) will be back here next April on a precursor cruise as part of that same project, picking up where we left off. You can be sure that all of us from this team will be doing all we can, whether ashore or at sea, to help support that program – just as Jon, Doug and their colleagues have been so supportive of our cruise this year. So don’t be surprised if you pick up this thread again, somewhere in the blogosphere, before too long. But before that, Jon, Doug and I will all be off on a different (but closely related) adventure – off to the Antarctic next January to dive on new vent-sites we have already tracked down on a similarly isolated stretch of mid-ocean ridge, down there.

So now, as I sign off, I just want to pay tribute to you the readers (both of you?) and, especially, everyone it has been my pleasure to sail with on this trip. Mark (Chief Enginer) paid us the great compliment this morning of telling me and Andy that he had never in his 18 years at sea enjoyed such a combination of good humored, well-motivated and professional research throughout such a long cruise. I can’t take credit for that – I’m just the chief cheerleader – but I do want to echo the sentiment. It has been a great privilege for me to come out here and (i) work with the Nereus engineers as they put their new robot through its paces, (ii) share with my international research colleagues as we have made a series of REALLY cool scientific discoveries (specially considering I thought there was only a 50:50 chance that the MCR might host any hydrothermal activity in the first place) and (iii) achieve all the above in the fantastic environment provided by Captain Dale and his crew whose support, dedication and interest in our work has made all the difference to what we have managed to get done. The RV Cape Hatteras truly has lived up to its reputation as “the little ship that can” and I hope I soon get the chance to sail with her again.

Message ends.

Thursday, November 5, 2009

Down to the wire

Not exactly fireworks (it is bonfire night back home in the UK today) – but these wiggly lines were enough to put a smile on our faces this afternoon. The green trace, whenever it plunges down the screen, is from Ko-ichi’s Eh sensor and tells us when we are closest to the plume source. The blue trace shows the depth of our instrument package as it varies with time (the axis across the bottom of the screen) as we pulled the CTD along behind the ship, lowering and raising it through the water screen. It’s not quite as exciting as watching hydrothermal vents and animals via video cameras would have been but as some of us enter our 5th week out at sea, its amazing what simple pleasures you can glean from just about anything!

Will we, won’t we??? This afternoon the wind-speed has been down in the Nereus comfort zone of 10-15 knots although not often at Andy’s favourite of less than 11 knots. So what will the next 24 hours bring? Will the weather continue to subside, or will it get worse again? Our vehicle is ready, our scientists are ready, and we know exactly where to go. But without a guaranteed 12 hour good weather window, we still won’t be able to launch Nereus and get the final job done. Sickeningly, the longer-term forecast DOES say that the weather will improve here after Sunday. But by then, most of our team will have jumped ship in the Cayman Islands and the rest of us will be on passage back to the Cape Hatteras’ home port in Beaufort, North Carolina.

Position at 11h30 EDT – CTD 56
Lat: 18° 32’N Long: 081° 44’W
Water depth: ~4850m

Funny how fast things can change at sea. We finally got the CTD working again last night after about 8 hours becalmed in vent-infested waters and have made out like bandits ever since. Actually that’s not quite exactly true. Due to a slight miscommunication error we ran a 6 hour tow-yo between suppertime and midnight last night that didn’t go right through our strongest plumes from earlier in the cruise as planned but, instead, flew past about 400m to the south and measured nothing, all the way. So we have the southern limits to where the vents can be REALLY well constrained now. Overnight we sailed back to our shallow site about 15 miles SW of here and lowered the CTD just before breakfast. The in situ sensor data didn’t look specially promising there , either, but we collected samples from each 50m up above the seafloor anyway and were duly rewarded for our persistence. Jeff and Jill measured the highest dissolved methane concentrations of the trip – by about a factor of two – in their samples from that cast and so we also collected samples for everything else we came equipped to sample for: metals, helium isotopes and microbial studies. Not bad for an early morning shift.

This afternoon the work got even better. We lined our CTD tow-yo run back up (in the correct position, this time) and ran a line that went right over the vent-site. The 30 minutes when we were right in the core of the plume not only coincide with our two previous strongest sets of anomalies (1 each from Leg 1 and Leg 2) but also coincide with when we were passing directly over a small semicircular feature that is about 200m across and 20m high, sticking out from the base of a volcanic cliff. How do we know it is sticking out from a volcanic cliff? Because it is the SAME cliff that we dived on with Nereus last weekend! Honestly – we were within 200m of the vents, twice, earlier in the cruise: on our last dive with Nereus in AUV mode on Leg 1 and our first proper dive in ROV mode earlier in Leg 2. Unfortunately, being 200m off still counts as a long way away when your mapping device can only see 40m to a side and your cameras can only see 10m or less in any direction. Call that a swing and a miss.

But there’s no point feeling sorry for ourselves and wondering “what if?”. This evening we are lowering the CTD back down, right over the site, in the hope of collecting another complete set of great samples, just like we collected at the shallow site this morning. And we’re also keeping a close eye on the weather. Our forecasts continue to be grim but this afternoon the winds have been below 15 knots when they were predicted to be closer to 20 and the waves were definitely lower than yesterday. If things continued in that trend we could still be in with a shout. Trouble is, that is NOT what is predicted and its no good launching Nereus just because the weather is good now. It is what the weather will be like 12 hours later, when we need to be able to bring the vehicle safely back aboard that matters. So we’ll remain poised and ready – like coiled springs – and optimistic right up until our time runs out:– about 36 hours from now. In the meantime, I have just remembered that we do also have one other last trick up our sleeve. Although we don’t have much variety of scientific gear aboard ship – after we had loaded Nereus and the CTD there wasn’t room for much more – we do have a small grab system that we could mount on the bottom of the CTD cable, instead of the CTD itself. So if tomorrow comes around, and we do already have all the water samples from here that we need, then even if Nereus still cannot be launched, we may yet be able to get David, Julie and Max some pretty cool samples from the seafloor.

We’re definitely not done yet - but I’ll still keep hoping for that one last Nereus dive…

Wednesday, November 4, 2009

If it wasn’t for bad luck…

Leaving it’s mark(er). When we come back here in future – and we surely will – this little marker on the seafloor will provide a “reality check” between one cruise’s navigation systems and the next – as well as a lasting testimony of some of the challenges faced, and the contributions made to deep submergence research by “the little ship that can” and all who sailed with her to get us this far along our path.
Position at 14h00 EDT – Too rough for Nereus, CTD undergoing repairs
Lat: 18° 31’N Long: 081° 44’W
Water depth: ~4850m

… we wouldn’t have any luck at all, it seems. When you’re out at sea you sometimes just have to take a few knocks and keep going. Where that becomes tough is when the knocks keep coming from various directions. Here’s yesterday’s tales of woe:-

1. Deceived by bathymetry. On Monday night we thought we had the source of a low-temperature site narrowed down because the source, based on depth, should have been on top of one of two small hills: the only places shallow enough to be responsible. Trouble was, when we landed with Nereus, the depths on our map were out by about 150m or so. This made our search area (everywhere shallower than 2150m) about 10 times bigger than anticipated. We searched hard for 10 hours and got lots of information about where the Eh signals were getting stronger and weaker in the water column, but we eventually got to the point where we couldn’t double back on our fiber. The final piece of evidence showed the source was still to the south of us, but all we could do was go north – and we were out of battery power anyway. So we left one of our markers at the seafloor to show where we left off – anchored, instead of the usual dive-weights, with a coffee mug of the RV Cape Hatteras (a ship’s tradition we were happy to help continue) and headed back up.

2. Deceived by sensors. Something else we found out during that last Nereus dive. When you are driving across the seafloor and then stop, our temperature sensor gets warmed up and, if you stay put long enough, the warming effect (because you aren’t constantly driving forward into fresh cold water, can also cause small signals on the Eh electrode. We found this out by stopping to look at some outcrops of old lava covered by sediment on this last dive. Nothing hydrothermal in site, but when we moved off, our sensor data had recorded anomalies just as big as the ones Nereus had collected at the end of Leg 1 while making a map close above the seafloor. There, the biggest anomalies coincided with when the vehicle – in autonomous mode, was having to climb the steepest terrain: across the very top of the volcanic hill and when approaching the base of, and rising up , some steep cliffs. Both locations looked attractive as potential hydrothermal sites – so the same data set had fooled three of us, each working independently to select where we should dive with the ROV to make sure we didn’t make a mistake. So how did we get that wrong? Well, steep terrain like that is also exactly where Nereus, in autonomous mode, would have been most likely to have to slow down and take time to adjust its dive plane before climbing vertically up and over the seafloor. And that slowing down process, we now know, could be just as capable of generating anomalies in temperature and Eh: signals we had mistaken for a hillside covered in weak diffuse hydrothermal flow.

3. Heart-broken by the weather. Even though we had spent two ROV dives – and had been preparing for a third - chasing after false signals in our sensor data, we still could have been in good shape for the rest of the cruise. Whatever else happened, we still knew of one high-temperature site that should be present in our search area. We don’t think it is likely to be the source of most of the plume signals we have been detecting but it is less than a mile from the deeper hill we had dived on previously. We found it rather by accident on an early Nereus dive when our compass went wrong, so we don’t have the greatest navigation data to show exactly where it is. But even so, we believe we know where to go to within 100m on the seabed because between 35 and 36 minutes past midnight, on an evening dating from about 2 weeks ago, Nereus passed through a column of hot, smokey water while driving around just 120m above the seabed. So last night we went back through what data we could salvage from that work to decide exactly where Nereus should dive next as an ROV. We got up this morning (most of the Nereus team were up at 5am) to prepare everything for launch, and then waited for the latest weather forecast. Which told us that the weather was due to turn worse today and might continue to get worse still for the rest of the week. Given the problems we had at the end of Leg 1 we had no choice. We had to postpone today’s dive until further notice and hope that, for the first time in a while, the weather forecasters will be proven wrong

4. Let down by our trusty CTD. You wonder whether your time’s up when even your best friends turn against you. Given that the sun is shining, the sea is blue, and there is a fresh breeze blowing, even the fact that we still couldn’t launch Nereus this morning didn’t have me too downhearted. There was still much to learn and interesting samples to be taken with the CTD that has been a trusty work-horse since the cruise began. But overnight last night and into today, even that has begun to get its own ideas about how many more times it wants to be deployed. Since 8am this morning we checked through everywhere we have already been in our area and where is left that the big vent-site we are after has left to hide. With another 12 hours of work we reckon we would be ready to lower the CTD right onto the site. Even if we couldn’t launch Nereus again in our last 3 days, that would still be pretty cool to achieve. But maybe the CTD has become self-aware and doesn’t want to risk getting its feet scorched? Because on 3 attempts since 10m, it has thrown up technical problems when we’ve tried to put it to work. Poor Steve is doing his best but it must be frustrating – Chris and Daniel have volunteered their help from the Nereus team (they are frustrated in a different way because they don’t have any ROV driving to do) but there is a limit to what any of the rest of us can do but sit here and wait.

As I said to Andy just before lunch: “A weaker person might begin to feel discouraged at this point.” But I’m probably just flattering myself there – weaker should probably be replaced by “smarter” or, at the very least, “less stubborn”. But we still have 60 hours left (psychological trick: sounds bigger than just 2 and a half days) so hope springs eternal - no point coming all this way and then not doing as much as you possibly can, right up to the end.

Monday, November 2, 2009

Decisions, decisions…

David and Julie H (from our ship) wave off our recent visitors – science colleagues Julie S and Cindy, flanked by Ari and Mark from National Geographic. They may have taken two of our scientists away but we traded them for Katy, their field producer, who will continue to ride the ship with us all the way back to Grand Cayman at the end of this week.

The tug boat Sand Cay as it departs for Grand Cayman - we'll see this little boat again in just a few days when we drop most of the rest of the science crew off.
Position at 16h00 EDT – End of CTD 49
Lat: 18° 21’N Long: 081° 51’W
Water depth: ~2500m

At times like this, when time is closing in on us, working out how to make use of the last few days of the cruise can prove quite tricky. Last night we finally got a good dive to the seafloor. Trouble is, the seafloor wasn’t quite so good to us. We landed on piles of lava with varying amounts of sediment and for the entire dive that is pretty much what we saw, everywhere, all the way up one side of the hill we had targeted (although we didn’t stop to look too closely, anticipating there were vents up the top) and all the way back down the other side. At around 6am it was time call things quits and bring Nereus back home. So what to do next?

Looking ahead we came up with a range of plans: (a) go back down and survey the other half of the same hill more thoroughly in the hope that it would be more rewarding than last night’s dive; (b) pursue a different set of plume signals from Leg 1 that were not so strong but might be easier to locate on the seafloor; (c) drive up a long-lived fault half-way down the ridge where hydrothermally altered rocks had previously been located or (d) dive to the top of that same shallow hill based on a hunch that the high concentrations of dissolved methane that we found at shallow depths in the southern half of the ridge on Leg 1 might be coming from their summit.

To follow up on the latter idea we conducted two more CTD stations this afternoon just off the top of that large feature (termed a detachment fault or, more poetically, a Mega-Mullion) which showed up both in the dissolved methane concentrations Jill & Jeff measured as in Ko-ichi’s Eh electrode sensor data. Gambling that we may have tracked those signals down to one of two shallow hills atop the very summit, that is what we’re going after in Nereus dive 26 tonight.

Not least in our minds when reaching this decision is the news that our good weather window may already be up – so diving to a target at 2100m rather than ~5000m means we may at least manage to get one more good complete dive in before weather issues mean we have to call Nereus back. Sad to think this might be our last Nereus dive, just a day after we got our first good one in ROV mode, but as I suspect I mentioned more than once in Leg 1, sometimes at sea you just have to accept what Nature provides and do the best you can with it.

Given that we came out of Florida 4 weeks ago not knowing if there would even be evidence of active venting anywhere on the Mid-Cayman Rise, I guess it would be churlish to do anything else but be happy with what we have already achieved, scientifically. And the fact that we successfully drove a deep diving submersible around for something like 10 hours yesterday at the bottom of a very deep ocean, from the back of a rather small research ship, is something that should make both our Nereus engineers and the Cape Hatteras crew very proud – if that doesn’t set some kind of new world record, I would be very surprised.

Our last bot of news for today is that we had more cruise members set off for home. Our friends from National Geographic TV had sailed down to meet up with us over the weekend but this morning, right after Nereus was on deck, it was time for them – plus our science colleagues Cindy and Julie S – to depart back to shore: don’t worry, they left Katy from the NatGeo team with us in case we do yet make that final “Eureka” breakthrough before the week is out.

What I have to start facing up to, however, is the worst case possibility that, having overcome the concerns that maybe we would have NO hydrothermal signals to pursue in Leg 2 we would, instead, have a multitude of interesting potential targets and yet still not get the opportunity to follow any one of them all the way back to their source at the seabed.