Articles tagged with: At sea

Departure!

Written by Maria Tsekhmistrenko on Saturday, 29 September 2012. Posted in Cruise 2012

28 September 2012

This is what we have been waiting for: 48 ocean bottom seismometers (Picture: Chris Scheingraber).

Anxious waiting, nervous faces all around. But suddenly the tension melts away, gives way to joy. There they are!

Our four containers are finally being released; the harbor workers are pulling up in two big trucks. They have lifted their strike after one week. To say that we are "relieved" would be a gross understatement. After days of forced inactivity, the ship becomes happily busy. Our bulky ocean bottom seismometers are being unloaded from the containers by our technicians, and the ship crew hoists them onto the helicopter deck with cranes. It takes us about three hours, and now only a cyclope could keep us from leaving.

20120928 01 container

At 3 p.m. everything is ready for departure. While the pilot is coming onboard and the crew is pulling in the ropes, the scientists are assembling on the superstructure in front, facing the harbor exit and the Indian Ocean. The sky is cloudy, it is drizzling, but nobody minds in the least – we are finally underway!

The harbor episode due to the strike already felt like an odyssey in itself, but now the real work is coming up. Still, we have used to time to get to know each other better and to bond. Our international group should be working together all the better for it.

First ocean-bottom seismometer deployed.

Written by Chris Scheingraber, Simon Stähler on Sunday, 30 September 2012. Posted in Cruise 2012

29. September 2012

First ocean-bottom seismometer deployed (Picture: Chris Scheingraber).

During the first day spent entirely on the sea, we set up the lab, tested the release mechanisms for the ocean-bottom seismometers, and successfully deployed the first seismometer.

Fully operational

Written by Chris Scheingraber, Maria Tsekhmistrenko on Tuesday, 02 October 2012. Posted in Cruise 2012

30 September 2012

Our colleague Olivier makes a quick cell phone call while the Marion Dufresne passes his native island of Rodrigues (500 km east of Mauritius, 33,000 inhabitants). (Photo: Karin Sigloch)

It seems like an endless and beautiful ocean is surrounding us. The last island on our journey (Rodrigues) rolled by hours ago, the last ship this morning. After the release of the first seismometer and a small celebration given by IPEV to honor this moment, we are getting into a daily routine.
Some of the scientists are working on recording and controlling bathymetry, gravity and magnetic data, while a smaller part are preparing seismometers for deployment. 24 hours a day, there is continuous activity. The OBS deployment teams do not care about meals or bedtimes, they have to be ready at all times. Even though we miss out on sleep and only rarely find the time to sit together and have a chat, we are definitely much happier with these circumstances than we were during the strike.

The workshop: ocean-bottom seismometers ready to take a dive. (Photo: Karin Sigloch)

La Vie en Rose

Written by Carmen Gaina on Wednesday, 03 October 2012. Posted in Cruise 2012

Or Science is really fun, enroll now ! (3 Oct 2012)

Rainbow and sunset over Mauritius Island

One has to be careful when making wishes: they may come true, and then you need to deal with the happiness overdose! For many years I was hoping to join a scientific cruise on a French vessel – I suppose the combination of learning from accomplished marine scientists and having French cuisine in the same time was the epitome of cruise experience for me. And voila – my wish was granted when one of the PI of this expedition, Karin Sigloch, kindly invited me to take part not only in a cruise on a French vessel, but also to experience an amazing adventure: peering into the deep oceans and then into the Deep-deep earth!

In less than one week we crossed fracture zones, mid-ocean ridges and volcanic edifices going through the evolution of the ocean floor like a quick tour from Rome, to Verona and than Milano, from ancient history to modern era. OBS deployments are our daily source of joy once they are delivered to the sea by a team of careful parents who want to make sure they prepared their children for their one-year foreign experience. The joy will be even greater next year when these children will come back full of knowledge from their year spent on the sea bottom – and then the mysteries of the Deep Earth will be finally revealed.
But for now we enjoy the rich life on boat –and the French cuisine, and the almost constant 22-23 degrees air temperature (water temperature is even better-but for various reasons we cannot enjoy that), and gorgeous sunsets and a bunch of amazing people.

The Marion Dufresne community is wonderfully diverse: the learned professors and senior scientists are happily playing basketball with the enthusiastic students – that is, of course, when their presence is not required for solving the scientific tasks, the multi-origin crew (among them French, Malgasy and Romanians) try to run smoothly the life on boat, and French (and English, and German, and some other languages) conversations around the table (whether in the laboratories, restaurant or seminar room) revolve around every imaginable subject – from seismology to marine biology, from George Clooney to GO, and from chili to best military airplanes.

My sunny life for the past two weeks had only one shadow: I missed the only lunch that served éclairs for desert!

To drop or not to drop?

Written by Karin Sigloch on Thursday, 04 October 2012. Posted in Cruise 2012

4 October 2012

Annotated map describing an OBS deployment (station RR17). (Read more bellow)

Among our most crucial decisions is where on the seafloor to drop our seismometers. Geometrically, the task is not unlike dropping them from an airplane at 3-6 km altitude, hoping that they will land in a suitable spot. Some luck is needed, because the seafloor is not mapped down to the meter scale, and because ocean currents can carry the OBS away laterally by several hundreds of meters before they reach the seafloor.

However, careful preparation can maximize the chances of a successful landing. The most basic requirement: the instrument should be recoverable when called to return to the surface – that may not be possible if it landed in a crevasse or tumbled over on a steep slope. Hence we seek out relatively flat spots of at least 1 km2 area. Such places can be found even in (underwater) mountain ranges, but dropping an OBS there requires more preparation than on a vast abyssal plain.

The other morning we had a challenging case, a targeted OBS site on the steep flank of the Mascarene plateau. The only prior bathymetry information came from "Sandwell", a jargon referring to maps extrapolated from measurements of gravity satellites – very smoothed and blurry sea-scapes compared to reality, but much better than nothing (see annotated map). "Sandwell" suggested a little flat embayment in the plateau flank, but as we approached, the highly-resolving ship bathymeter gradually revealed a steeply incised canyon, 2800 m beneath the surface. No sediments to flatten out even a small area. We collectively pondered the evolving scene, and imagined mud avalanches rushing down the canyon channel. Fact or fiction? No way to tell. It seemed unwise to drop the OBS there.

With not many options available, we targeted a small protruding ledge a few miles up-flank on Sandwell's map. The approach was steep and unpromising, but suddenly sediments started showing up on the screen of the sediment sounder. The saddle area turned out to be narrower and shifted compared to the Sandwell prediction, but 1.5 miles wide and reasonably flat seemed lucky under the circumstances. We dropped the OBS above the likely equivalent of an Alpine meadow, bounded by a steeply incised mountain stream, perhaps with bottom-dwelling fish instead of grazing cows. It had taken us two hours, but had also satisfied our curiosity. Expert bathymetrist Jérôme summed it up: "Interesting – so that's what a canyon may look like for Sandwell."

* Picture Caption : 

Annotated map describing an OBS deployment (station RR17). Before our arrival, we had only the blurry bathymetric information that fills most of the picture (“Sandwell”, extrapolated from gravity satellite measurements). In real time, we replaced a ~10 km wide swath beneath our ship track with the ship’s own, more highly resolving measurements (top left to bottom right). It revealed that the seafloor in this area was not smooth at all – it took some cruising to find even a small flat spot.

Floating seminar

Written by William Jason Morgan on Thursday, 04 October 2012. Posted in Cruise 2012

4 October 2012

Detailed bathymetry measured by our ship has been laid over a coarser, pre-existing deep-ocean map. Note the canyon that appears on the highly resolved swath. The swath is about 10 km wide, the canyon is located around 3000 m depth.

One of the more interesting aspects of a research cruise is the 'floating seminar' atmosphere. I don't mean the daily afternoon presentations in the conference room by one of the cruise participants, as interesting as they are, I mean the daily interactions of persons with various specialties from various institutions all focused on a single research project. Seeing how the ocean bottom seismometers (OBSs) are assembled, tested, deployed over the side (gently!); having discussions of what can go wrong, tales of past mistakes, improvements being made all give one a better understanding of how a seismic experiment is planned and executed far beyond what one can get from reading journal articles of OBS results.

Another center of activity and discussion is the monitor screen that displays each 'sweep' of the incoming bathymetric data. The 'multibeam' bathymetry of the Marion Dufresne has acoustic sensors that look not only straight down to the seafloor but also are aimed outward to receive echos from many angles away from straight down. Then the return echos of the many sensors are put together in the system's computer, and a 'swath' of bathymetry is produced. The moving ship results in a ≈5-km-wide ribbon of seafloor depths mapped, analogous to laying out a series of aerial photographs for land mapping.

The general locations of each OBS site were selected when the experiment was planned, but the precise location for a 'drop' is made while looking at the bathymetry collected at the site. At this time, many eyes gather in the lab around the bathymetric screen -- all looking for that perfect flat, not too rocky, not too steep spot on the ocean floor. Lots of murmur in the peanut gallery as Karin and Guilhem make the final choice -- sometimes the initial 'X' is abandoned and a 'better' place several kilometers away is selected instead.

The bathymetric screen showing the swath of bathymetry collected as we steam from drop-point to drop-point is a constant focus of interest. Many so-called "seafloor canyons" have been seen in the swaths. These features are tens of meters deep and hundreds of meters wide; they are commonly made by avalanches on the steep slopes of continental shelves which create a fast moving mixture of water and suspended sand which cuts away the flat mud on the seafloor much like a river cuts away land surface. Near continents, such 'canyons' can be traced for hundreds of kilometers; the source here mid-ocean would most likely be collapse of the slopes around the carbonate banks and islands of the Mascarene Plateau. Our cruise isn't mapping them -- following them from beginning to end -- but we have crossed and noted perhaps a half-dozen on our zig-zag path from site to site and wonder collectively where and how each may have originated.

And last night the sky was brilliant; a bright Milky Way and the bow of the ship pointing directly toward the Southern Cross.

A life after the Marion Dufresne?

Written by Maria Tsekhmistrenko on Sunday, 28 October 2012. Posted in Cruise 2012

25 October 2012

The last day has broken. Only a few hours left before we have to leave the ship. For the first time in weeks we are going to feel firm ground under our feet. We are leaving the ship, which was like home for us, though for a relatively short time.

 SAM 2233

Over the past days, I wistfully I enjoyed my coffee on my favorite outlook spot on the deck. I never got bored of the beautiful view of the ocean, and every day I enjoyed it more. While sitting here, I remembered many moments on this ship:

Jeans “plat au fromage”; Patrik, our best friend behind the bar; Chris trying hard to find some people to play baby foot with him after each meal; Henning’s long way down to get his “big, black, bad” – coffee; Karin and Gulihem trying to find the perfect deployment point for the OBS; Sacha’s tireless night shifts, which helped to sit out the long hours; Heiner playing Guitar; Oliver’s daily search for the next seminar speaker; the united march of the officers to the dinner table; the deployments, the Marion Dufresne, the ocean…

Thanks to all of you taking part in the cruise (LEG 1 and 2). Thanks for the unbelievably great, exciting, educational, fascinating and definitely unforgettable time on this ship. 

Here we go again!

Written by Maria Tsekhmistrenko on Friday, 25 October 2013. Posted in Cruise 2013

12000 km of total route length to go. 57 OBS are waiting for us in the deep abyss of the Indian ocean. 43 days at sea. 24 scientists gathered on the the magnificent Meteor. 10 knots of mean velocity. 2 Legs. 1 big Project. RHUM-RUM.

One year later, one year of waiting, one year of unbearable curiosity. We are back to recover the OBS we deployed one year ago. After this time the ocean bottom seismometer had enough time to gather a lot of data.

The recovery has now started and with each new OBS safely recovered, we gather more data. Valuable data for our project to image the hot spot below La Reunion. But will the instruments deliver the expected and needed data?

Still 44 days to got and 54 OBS to recover to find this out.

 

Operational

Written by Karin Sigloch on Monday, 28 October 2013.

27 October 2013, 18°05'S 62°06'E, Karin Sigloch

The first four days on sea have passed very quickly. We had to get operational without delay: the first recovery of an ocean-bottom seismometer (OBS) happened only six hours after leaving Port Louis. Since then we have recovered eight instruments, and have experienced various weather conditions and technical quirks. Calling an instrument back after 13 months on the seafloor is the hour of truth: was everything done right and did the technology work?

Recovery is straightforward in principle. The ship navigates to the spot where the OBS was deployed last year. We send a short sequence of acoustic pings into the water using the ship's hydrophone. The instrument recognizes its "name" (unique code of pings) and turns a little hook to detach itself and its buoy from the iron anchor that has kept the whole assemblage down. It takes 30-60 minutes to rise to the surface where it is easily noticeable by its flasher, its radio beacon, and its bright orange colour. Only that in practice, things needn't be easy on the open ocean. The acoustic link down to 3000-5000 m is variable, the salt water is corrosive and may have damaged electrical connections or batteries, and high waves or poor visibility can make it difficult to spot the instrument and to hoist it onboard.

We were lucky that during the first few days the weather was sunny and the sea was calm -- good conditions for getting into working mode. For the next few days, a tropical storm will be our companion, travelling westward just as we are, just a few hundred kilometres to the north. Rain, higher waves, and a more physical recovery experience this morning gave us a first taste.

 

Recovery of our first ocean-bottom seismometer RR17 on a bright day and a calm sea.

 

Our latest recovery of an OBS as we entered the fringes of a tropical storm system.

 

 

New Diving Paradise Discovered

Written by Heiner Igel on Wednesday, 30 October 2013. Posted in Cruise 2013

30 October 2013, Heiner Igel

Looking for a nice spot to do some deep diving? Not too touristy? Well, here’s the place. Last night at around 2am (I admit I was off-shift and sleeping) we came across a spectacular feature of the Indian Ocean’s topography: a seamount.  The average water depth in the area here between Madagascar and La Réunion is about 5000m. Within a few miles this seabottom topography rises to only about 50m water depth! Picture something like Mt. Blanc under the water surface and you are not far off! It s about the same dimension.

Seamounts are a fascinating feature of our planet! They are mostly extinct volcanos that were eroded by the sea and no longer appear as islands. There is an estimated 100.000 (!) seamounts under the oceans and many  of them wait to be explored. The one we moved over last night is known from satellite based seafloor topography estimates (so, ok we did not really “discover” it) but we are the first to map it precisely with  sonar depth mapping techniques.
This mapping technique sends sonar signals into the water and produces images just like the ones we know from medical imaging. Yes, and sometimes people come into the monitoring room, look at the screen and say “oh, look it’s a boy!”.
Yann, our experienced diver tells us that  50m depth is something that still can be reached by scuba-diving. It is likely to be an extremely rich and interesting environment from a biological point of view similar to corral reefs. So consider this for your next diving vacation. But beware the next bar is about 500km away!
 
Heiner
 

 

Swell

Written by Karin Sigloch on Wednesday, 30 October 2013. Posted in Cruise 2013

29 October 2013, Karin Sigloch

 

Swell on the open ocean (from last year’s cruise).

 

The tropical storm to our north was downgraded to “a tropical depression without development potential” – uplifting news to most of us. We did experience substantial winds and especially waves over the past days. Especially during meal times in the bow of the ship, we felt the blows to our stomachs.

Interestingly, the waves originated mostly not from the nearby storm but were “swell”, i.e., far-travelled wave trains generated by distant storms, mainly in the Southern Ocean. Experiencing the swell first hand is interesting to a seismologist because it causes most of what we consider “noise” in seismograms: unwanted signal that obscures “useful” features, like earthquakes. Through a non-linear coupling process that still awaits full explanation, the shallow water waves of the swell couple into the solid earth along coastlines and rough seafloor topography. Thus a small amount of water wave energy is converted into seismic waves that travel through the earth’s interior to seismological stations worldwide.

This “microseismic noise” is present on any kind of seismological recording, even in the middle of continents, but it is particularly pronounced on ocean-bottom sensors, which are sitting in the middle of the action, so to speak. As we have perused through our newly acquired data, it has been slightly sobering to realize the signal-processing challenge that this noise will present. The swell is a big nuisance to as seismologist, but going to sea can teach something like acceptance: if the swell is so real on my stomach, no wonder it is real on my data…

 

Waves

Written by Jason Phipps Morgan on Wednesday, 30 October 2013. Posted in Cruise 2013

29 October 2013, Jason Phipps Morgan

 

On a ship, one thing you can do as much as you wish is look at waves. But the usual measurements that weathermen use to characterize the surface of the sea don’t do full justice to the many moods and flavors of swell, ripples, glass, whitecaps, Poseidon’s chariots... that often fill a day at sea.

Usually the marine weather report will quantify the likely sizes of waves and wind, both the waveheight of the shorter choppier breaks that are formed by winds nearby, and the swell, the longer rolling waves that sway and vibrate a ship and tell of far off storms, that even let you dead reckon under a cloudy sky if you assume that they point away from a particular stormbelt like the high latitudes to the south.

Size does matter, but waves have many unique flavors and can change throughout a day. Around noon, we had a short rainstorm from a mild tropical depression that has been slowly following us the past few days, giving us grey clouds and rain to protect us from the blue sky. After the rainburst, the sea surface became a mosaic of tiny crinkly ripples forming, mutating, and disappearing above a semi-glassy ~2 meter swell. The swell was big enough to rock the ship as each wave moved at a speed like a running horse, and the tiny crinkles scurrying over the moving swell seemed almost alive. So different from the similar sized swell with choppy whitecaps that had preceded the squall.

Progress

Written by Karin Sigloch on Wednesday, 06 November 2013. Posted in Cruise 2013

6 November 2013, Karin Sigloch

 We have fallen behind on blogging during a very busy week. As we are nearing the end of Leg 1 of the cruise, we have recovered 26 ocean-bottom seismometers. So far, every instrument has responded to our calls and returned from the seafloor – the most basic measure of success. Most instruments have done their job, but not all. A few have returned without data, or only hydrophone data, and some have drained their batteries prematurely. We are sorting through large quantities of recorded time series and engineering log files, trying to understand what we have obtained in each case, and why.

Compared to the variety of complications encountered in data logging and seismometer hardware, OBS recovery operations have been quite smooth. We found that the rise time of an OBS, typically 50-70 minutes depending on depth, can be predicted to within one or two minutes. Even better, the Meteor was recently equipped with a directional radio receiver that has so far detected every surfaced OBS by its emitted radio signals – often long before our handheld radio device or eyes could have. Compared to tales of heroic search attempts in the dark ages, it has become almost too easy – but such is progress, and we love the goniometer’s beep that heralds the arrival of yet another seismometer.

While the Meteor’s officers and skilled deck crew have perfected their techniques for getting the instruments on board, some of us have perfected their documentation skills. The two photos are extracts from an underwater movie of a recent recovery.

 

 RR04 has been approached and is floating in on the starboard side of the Meteor, in an absolutely calm sea – “duck pond weather”.

 

Seconds before it is pulled out of the ocean by the ship’s crane, RR04 has to roll around – a moment captured by Guilhem’s underwater camera strapped to a long sailor’s rod.

 

Flying fishes

Written by Edith Korger, Simon Stähler on Tuesday, 12 November 2013. Posted in Cruise 2013

Animals of the sea are surprisingly rarely sighted. Near the islands you can see dolphins which sometimes come to investigate the ship, and you sometimes sight swordfishes which cut across the sea. But if you stand on deck, the sea most often seems empty of life. In this latitudes, flying fishes are almost omnipresent. Before I first joined a scientific expedition, I only knew them as a dimly remembered cartoon in a childs book, and as a bizarre art form of nature which has been captured on a photo in my parents living room. I did not expect to actually see a flying fish in its natural environment.
In the southern sky you can see a combination of six stars (maximum brightness about 3 – which means it is substantially less bright than the polar star) at night, which a dutch sailor has named “flying fish”. The southern hemisphere, regardless of land or sky, has been charted under pressure of time by the first European explorers. So, in contrast to the northern sky, you will find there mostly nautical constellations (e.g. Octant, Pendulum clock, Sword fish), or some constellations which are foreign to Europeans (e.g. Chameleon, Tukan, Table Mountain).
Actually if you stand at the bridge or at the bow, you often see swarms of small fishes. Flying fishes soar out of the water with flapping fins, gliding about 10 metres, and then with a small splash diving again. On some windless days last week, the flying fishes left behind a criss-cross pattern of small ripples on the sea, not unlikely pearl necklace. Here you can find a photo of a single flying fish, taken by Edith. I hope you enjoy it as much as I did.

Heading for the volcano

Written by Karin Sigloch on Saturday, 09 November 2013. Posted in Cruise 2013

9 November 2013

 

Group photo Leg 1. Since starting out from Mauritius 19 days ago, we have successfully recovered 28 OBS as planned, and have accomplished additional bathymetric mapping here and there. We have kept circling the central target of our seismological campaign, the hotspot of La Réunion. Now, during the last night of Leg 1, we are heading directly towards it. The Meteor should reach this spectacular volcanic island early in the morning, where the first half of our cruise will end.

 

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