Cruise 2013

Here we go again!

Written by Maria Tsekhmistrenko on vendredi, 25 octobre 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.

 

First shower in a year

Written by Karin Sigloch on lundi, 28 octobre 2013. Posted in Cruise 2013

28 October 2013, Karin Sigloch

OBS technician Edith is kärcher-ing seismometer RR12 with freshwater just minutes after it has been pulled on board. The narrow titanium cylinder that sticks out between the orange buoys is the release unit, which attached the assemblage to, and later detached it from, its heavy steel anchor. The anchor stays behind on the seafloor. The wide titanium tube that rests on the wooden pallet is the seismometer itself. The data logger and lithium batteries are contained in two horizontal titanium tubes on the opposite side of the buoys (barely visible in the photo). The orange rope contains a few loops by which the sailors fish up the OBS with their long hooks once it has resurfaced.

 

 

New Diving Paradise Discovered

Written by Heiner Igel on mercredi, 30 octobre 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 mercredi, 30 octobre 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 mercredi, 30 octobre 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.

Life onboard the METEOR vessel

Written by Edith Korger on jeudi, 31 octobre 2013. Posted in Cruise 2013

30 October 2013, Edith Korger

Let me tell you how you live on a research ship, apart from work. First, as Jason has told you, you could grab a mug of coffee, go out to the work deck if no recovery of OBS is currently going on, and look at waves and sky. You may or may not encounter others doing the same, and, if you are socially inclined, that would be a good reason to talk to each other. Another place you usually can find others seeking company is the lounge, at the bottom of the ship. Particularly in the evening it is a favourite haunt for off-duty people. Its dark wood and comfortable polstered chairs make sitting in there and listening to the onboard radio a treat.

There are a multitude of rooms on board. Apart from the individual cabins, there are ones which can be used for various purposes: The ones nearest the work deck are usually occupied, either by the recovery crew screwing around with - yes, screws - or by people analyzing the freshly gotten data. Then there is the computer room where you can send and receive mails, print selected information, and even, if you are patient, get access to the worldwide internet. The telephone booth is at the top of the ship near the bridge. A call to your people at home can be very reassuring, but you need to visit the booth when it is currently unoccupied!

You could also observe ship maneuvers on the bridge, but everyone on it must know you are there (i.e. announce yourself loudly), and you must not interrupt!

If you seek to be alone, you could go to the library and take a book, sitting quietly in a corner of the small room. Another good place to be alone is on some narrow walkway outside at a higher deck, as up and out there not much is going on. All the people having business are usually using the rooms and stairway in the inner part of the ship, as it is much more convenient to go from top to bottom using only a single long stairway, rather than running all around the outside of the ship with all its shorter and (at least at the start of the cruise) confusing exits and entries.
 
All in all, a research ship is both a bigger and a smaller place you probably imagine. Smaller, because if you really want to hide, this is very difficult. Usually someone sees you walking around and people will talk to each other. Bigger, because the ocean around you is so very boundless, and you just have to step outside to get the impression that everything is possible.

Meteor and Marion Dufresne, an unexpected rendez-vous in the Indian Ocean

Written by Guilhem Barruol on dimanche, 03 novembre 2013. Posted in Cruise 2013

2 November 2013, Guilhem Barruol

 

 The Marion Dufresne vessel that allowed us to deploy our ocean bottom seismometers in Oct-Nov 2012 was scheduled to leave La Réunion last Wednesday to make its rotation toward the Austral islands: Crozet, Kerguelen, Amsterdam and St Paul.  A technical problem did not allow the Marion to leave La Réunion on time and she finally departed on Saturday morning going southward to Crozet island, the first destination before Kerguelen. The probability that the two vessels that actively took part in the RHUM-RUM experiment could meet in the Indian Ocean was obviously very small due to the size of the Ocean but also due to our way of progressing in zig-zag from station to station with the vessel Meteor. 
This Sunday morning at 5 o'clock, the Meteor reached the position of the station RR24, the southernmost of our first leg. At  sunrise we discovered the Marion Dufresne at the horizon, she was approaching us. At 6:30, we were at about 5 miles from each other, and no doubt that the Marion crew has seen us as well as we have seen them. A really unexpected meeting in the sunrise light!
Other - and ultimate - coincidence: the station RR24 at which we met was the last of the 57 OBS deployed last year with the Marion Dufresne and that we celebrated on the back deck of the Marion on Oct 22, 2012. Be always careful with the probability!

We wish the Marion a good way for its Austral rotation!

Whales!

on mercredi, 06 novembre 2013. Posted in Cruise 2013

Today (the 5th of November) we had the chance to witness whales and dolphins at sunset time.

Many of us were watching an amazing sunset over an unbelievable quiet sea (like a mirror) when about 10 dolphins were seen. A few minutes later, something bigger, like a large piece of floating wood was in sight. A whale! or a “cachalot” … we are not sure. Then, shortly after the first one, 5 whales or cachalot were seen.
After more than two weeks on board seeing very little sea animals, what a great surprise. Unfortunately, some of us were unacceptably late for our daily seminar given by Heiner that day ;-p

Actually for two scientists of the cruise, including our speaker of the day, this is a great year for wild sea life watching, after a swim with whale sharks six month ago.

whale at sunset

Progress

Written by Karin Sigloch on mercredi, 06 novembre 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.

 

News from La Pérouse

Written by Karin Sigloch on samedi, 09 novembre 2013. Posted in Cruise 2013

8 November 2013, Karin Sigloch

Bathymetric data acquired on La Pérouse seamount, rendered by Carmen Gaina

Shortly before his beheading, Louis XIV is said to have asked for news from La Pérouse, the explorer whom he had sent on a famous expedition around the world, and who had gone missing the year before. It remains unclear who died first, the king in Paris or La Pérouse in the southwest Pacific, and we have no news on this matter.

But northeast of La Réunion, a very large seamount is named after La Pérouse. Satellites have long detected it thanks to its strong gravity signal, but during last year’s cruise, we were the first to map a fringe of it with high-resolution bathymetry. These are directed arrays of sound wave pings that the Meteor sends to the seafloor every 10 seconds, to map out its depth several kilometers to the left and right of the ship. This year we returned, and did two perpendicular passes across La Pérouse.

The first pass showed that it is flat-topped: a so-called guyot, probably topped and rimmed by drowned coral reefs – the first piece of news about La Pérouse. When we returned, the bathymetry in addition revealed huge submarine landslides along the flanks of the seamount.

On the bridge, it was amusing to watch colleagues excitedly crying “Only 60 meters deep! 55 meters!”, leaning over the railing to see if the shallow water would change color. Whereas the Meteor’s captain, watching his nautical chart made from low-resolution satellite data, was grumbling “It should be 2000 meters here…it should be 1500 meters…” In view of such large uncertainties about the seafloor, a point of practical importance occurs: the seamount’s corals did not rise quite as close to the surface as the reef that spelled the end of La Pérouse’s expedition 225 years ago.

 

Flying fishes

Written by Edith Korger, Simon Stähler on mardi, 12 novembre 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 samedi, 09 novembre 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.

 

Start of Leg 2

Written by Karin Sigloch on vendredi, 15 novembre 2013. Posted in Cruise 2013

12 November 2013, Karin Sigloch

Cruise and deployment map. The rainbow-colored background shows the structure and depth of the seafloor (in meters). Black lines mark the route we have taken during Leg 1, collecting 28 German ocean-bottom seismometers (red circles). During Leg 2, marked by red lines, we will collect both French and German instruments (blue and red symbols, respectively). We will also map the seafloor along our way, as during Leg 1, and deploy two “MERMAIDS”, which are prototypes of seismological Argo floats from the University of Nice. From the southernmost point of Leg 2 (station RR36) onward, we will be following the Southwest Indian, and later the Central Indian, spreading ridges. These are huge underwater mountain chains whose relatively shallow depths correspond to yellowish-orange colors on the map.

The second half of the cruise has started – we are on our way south. During a stopover of two days in Le Port de la Réunion, 11 scientist colleagues left and 9 new ones boarded the “Meteor”, including the French OBS team. Leg 2 will be an alternating collection of French and German OBS along a 6,000-km long track that circles around far south of La Réunion and follows two mid-oceanic ridges for much of the way (red line on the map).

 

Looking back on La Réunion a few hours after departure, the island with its up to 3000 meter high volcanoes is seen to act as a cloud catcher, while an intense tropical sun is shining on the surrounding ocean, including us.

First French recovery

Written by Karin Sigloch on vendredi, 15 novembre 2013. Posted in Cruise 2013

13 November 2013, Karin Sigloch

 

 Today in the earliest morning hours, we recovered the first French OBS (station RR28). The operation had been preceded by some additional technical preparations because this model needs to be approached by the ship even more carefully than its German counterpart, and it consists of two pieces that can start to swing as a double pendulum while being lifted out of the water. RR28 also didn’t reply to its release command (at least not audibly), leaving us to worry for three hours whether it would appear or not. When it finally did, its recovery went smoothly despite a relatively rough sea, and the seismometer has brought back very nice data.

 

Shark attack on the magnetometer

Written by Karin Sigloch on dimanche, 17 novembre 2013. Posted in Cruise 2013

16 November 2013, Karin Sigloch

 

 

Our magnetometer seems to have been bitten by a shark last night. We haul it on deck prior to every OBS recovery, and this morning it came in with significant damage. Its plastic casing bore scratch marks in numerous places and a couple of deep bite holes, from which the thick casing had cracked outward in irregular patterns.

 

 

Colleagues and the Meteor's crew were aware of similar assaults on towed equipment in the past. The magnetometer is 120 cm long and has a slender, fish-like shape. It is pulled along on a 250 meter long cable that transmits data to the ship in real time. Magnetometers could be particularly interesting to sharks because they generate weak electromagnetic fields, which the predators may be able to sense.

The interest is not mutual. The magnetometer measures neither biological signals nor properties of the water column. Rather its purpose is to record the magnetization that is "frozen" into oceanic crustal rocks, from the time each parcel of seafloor originated from molten lava along an oceanic spreading ridge. Magnetometers record spatially alternating patterns of seafloor magnetization as the ship passes over, and these patterns can be tied to the timescale of polarity flips of the earth's magnetic field. Together they tell the story of how ocean basins have originated, grown, and vanished over geological time. The part of the Indian Ocean we are currently passing through is particularly old, dating from times for which information about the configuration of continents and oceans is sparse. Unfortunately our magnetometer will have to stay on board for now, until we are convinced that its hull is still waterproof.

 

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