FAR-DWO DS1 cruise. Chasing submarine dense water overflows

The journey begins (16/07/2023)

We are already in Reykjavik! we had the most warm welcome with the Litli-Hrútur volcano and we are all ready for the set up of all the laboratories and instruments for the cruise.

Setting up the labs and instruments (17/07/2023)

We have now the labs prepared to do a bunch of water and sediment analyses during the cruise, and we have prepared the instrumented mooring lines. An awesome team effort! We also enjoyed some free time visiting Reykjavik and the surroundings.

(by Sara Espinosa Paz)

Stretching the legs before the cruise (18/07/2023)

After setting everything up in the lab, we had some free time. We were lucky to spend our afternoon-hiking visiting the Litli-Hrútur volcano in eruption. We bought some snacks and water and went for it!!! The hike was almost 20 km so we had to be prepared. Even though the path was not easy it was totally worth it.

(by Sara Espinosa Paz)

There we go! (19/07/2023)

11:30 a.m. we leave the harbour. THE CRUISE HAS OFICIALLY STARTED!!

We did the safety training and learned about ground rules onboard. Everythig is ready for the first sampling point. As a starting gift some whales gave us a warm welcome into the icelandic waters.

(by Sara Campderròs Serra)

First mooring deployed (20/07/2023)

First mooring successfully deployed in the Denmark Strait dense water overflow! It includes a downward looking acoustic Doppler current profilers (ADCP) to measure current velocities in the last 100 m of the water column, a single point currentmeter with a turbidimeter to detect light scattered by suspended particles, a high-accuracy conductivity and temperature recorder, and a sediment trap to collect settling particles. The mooring line was assembled on deck, and the deployment started with the surface buoys and continued with the line with the instruments until the acoustic release and anchor, that was dropped at 14:47 PM at a depth of 1326 m. The mooring will be recovered before the end of the cruise, and will be re-deployed again to perform measurements during an entire year.

(by Anna Sanchez-Vidal)

Station after station (21/07/2023)

We woke up with a very beautiful sunrise at 4 AM. A few hours later we started the CTD sampling in the first station located at 65º 30.17’N  24º34.57’W , with lovely views of the northern  coast of Iceland.

During some stations, we’ve sampled water and the monocorer was deployed. As we can see in the photos, the monocorer came back to the research vessel with some sediments of the Denmark Strait bottom. These are great news and motivate us to deploy a multicorer in a future station which implies more quantity of sediments to work on.

(by Helena Fos Serdà and Mara Navarro Buigues)

Go with the flow! (22/07/2023)

The work never stops at night onboard. While we sail facing towards Greenland, we have started the day by retrieving CTDs and sediment samples with the Van Veen dredge. Surprisingly, the seafloor at 500 m depth is plenty of pebbles!

We are now at 66º 12.74’ N 027º 38.42’, and the CTD is being dragged by large currents close to the seafloor. We notice this by seeing the wire that holds the CTD strongly tilted. At the same time, we observe a very cold-water mass (~ 1ºC) with high levels of oxygen in the CTD profile. This is keeping us very motivated because we might be very close to the biggest submarine cascade of the world!

(by Galderic Lastras and Marta Arjona)

Fog (23/07/2023)

The flat sea is our best ally during these first days of the cruise. Good weather in these latitudes come with very dense fog and the horizon merges with the sky. We are working 24/7 and making good progress towards the attainment of the project aims.

(by David Amblas)

Freezing views (24/07/2023)

The fog has given us a break and we have spotted two icebergs while sailing towards Greenland. A fantastic reward during the hard working shifts!

Today we did a scientific meeting to talk about the progress of the cruise. The results obtained so far are super interesting, we are so excited! We expect new findings during the cruise life and beyond, as many of the data and samples we are collecting will require a long lab process once we are back on land.

(by David Amblas)

A window to the past (25/07/2023)

The dense set of CTD profiles already acquired during the first week of the cruise shows us the great hydrodinamic complexity of the Denmark Strait, with strong water masses mixing in the top hundreds of meters, abrupt temperature drops, even below 0ºC!, and very strong currents.

We aim to infer changes in the oceanography of the strait as related to the global ocean circulation system by studying the sedimentary record. Sediments can preserve the history of the ocean by accumulating particles that inform us about the prevailing conditions on the water column, such as the origin of the water masses, the intensity of the currents or biological productivity changes. In FARDWO-DS1 cruise we are using different systems for sampling the sea floor. A monocorer attached to the CTD-rosette is used for the recovery of few centimeters of the sea floor in each station, thus being our spy. The Van Veen dredge allows us to obtain a significant volume of sediment, while a multicorer and a gravity corer can preserve the history of particles deposited in the sea floor.

We are recovering a significant amount of sediments that will be later analyzed in our in-land laboratories, a huge amout of work to be done in the future months!

(by Jaime Frigola Ferrer)

Wind blowing in our favor (26/07/2023)

After an agitated night at sea, with strong winds and big waves, the team woke up with good news! The storm that has been announced for days, forcing us to recalculate our itinerary, starts to vanish earlier than expected and so we will return to our original route towards the Greenland coast soon. Although better than expected, the wind does not allow us to continue doing any external operations such as CTDs, gravity core or multicore collection. In the meanwhile, we took the opportunity to start a bathymetric survey in an area of 1800 km ² . We are looking forward to discovering what surprises are hidden in the sea floor and what stories does it tells us.

(by Luisa Gonçalves de Freitas)

Here's a poem for AMOC (27/07/2023)

We are sailing on top of the Denmark Strait Overflow, one of the densest components of the Atlantic Meridional Overturning Circulation (AMOC) and, hence, a key element of the global climate system.

This paper, published in Nature a couple of days ago, raised controversy on the potential collapse of the AMOC in the coming decades. Here you have a poem that we kindly asked ChatGPT to write for us, in an attempt to add humour and literature to the discussion. The result is pretty neat, isn't it?

Meanwhile, we keep collecting oceanographic and geological data that will bring new light into the discussion.

(by David Amblas)

Here comes the sun (28/07/2023)

The last couple of days have been calm at the vessel. While the sonar was doing its job collecting the bathymetry, the team had some time to rest, socialize and do science (of course). Today the storm was officially over and the sun was finally out, but don’t forget that we are in the Arctic and even though it is summer the maximum temperature was of 2 degrees. With our energies recovered and the sun shining, we returned to the normal schedule of sampling water and sediments. We advanced on 8 CTD stations, sampled a few NIOZ monocore, collected a gravity core and gathered the first multicore with all tubes completely full of precious mud that were subsampled on the deck in cold conditions.

(by Luisa Gonçalves de Freitas)

Groundhog Day. Routine, routine, routine (30/07/2023)

07:00 AM, the alarm goes off. Breakfast time, we have churros! Today is Sunday. We are at the equator of the cruise and it's been a day since we crossed the Arctic Circle. Today is not a holiday or vacation day; the dynamics of the cruise continue and the map is filled with sampling station points. All the members of the cruise (scientists, technicians, and crew) know the sequence of operations: CTD, water sampling, sediment dredging, multicore, and gravity core.

Indeed, an oceanographic campaign is like "Groundhog Day," but without Dylan on the radio. You wake up with as little noise as possible; your cabin mate went to bed at 4 a.m. m. after returning with the overall covered in mud. Sediments are the "dirty" part of oceanography, having nothing to do with "dry" physics or "drab" bathymetry.

There are moments and days for everything, and today, Sunday, coincided with a sampling station at noon, right in front of the coast of Greenland. An incredible spectacle, with a bright and cold day surrounded by "brash" ice, mountains in the background with their glaciers and rocky peaks protruding over the ice, the nunataks. Even, we spotted some distant whales. But then it was time to get back to measuring the water's characteristics, collecting liters and liters of water at below 0°C, dealing with sticky sediments that dry out your skin and seep into every overall and jacket, with no way to wash them. They will serve as a reminder of the moments when seasickness plagued us during bad weather, our hands froze and dried up, and we questioned ourselves, "What am I doing here?" Yet, we had the opportunity to witness that iceberg with the nunatak in the background.

(by Antoni M. Calafat)

Goodbye Greenland (31/07/2023)

Tonight we left the Greenland coast and are now heading the inner area of the Denmark Strait, doing CTD profiles one after the other. We still see big icebergs in the horizon from time to time. Also whales and birds are being our inseparable travel mates in this journey.

Milking the CTD (01/08/2023)

CTD profile number 120 onboard RV Sarmiento de Gamboa! The CTD (standing for Conductivity, Temperature, and Depth) is our vital instrument to define water masses in the Denmark Strait based on temperature and salinity but also measures oxygen, turbidity & transmissivity, fluorescence, and pH. The CTD is attached to a water sampling array known as a rosette that collects water from different depths. Once onboard the water sampling party starts: we are filtering water from the Niskin bottles for total suspended matter (to calibrate turbidity sensors), elemental composition (C, N) and stable isotopic composition (d13C and d15N) of organic matter, lipid biomarker characterization, diatom floristics and biogeochemistry, microbial populations, and chemical analyses (Nd isotopes and REEs). Such a multidisciplinary particle characterization will allow us to study the detailed biogeochemical signature of the dense water overflow, which has remained largely unexplored.

(by Anna Sanchez-Vidal)

Order, Clean, Label (02/08/2023)

People who study the ocean are oceanographers or oceanologists. An oceanographic cruise is composed of geologists, chemists, biologists, or physicists who study a specific part of the ocean that interests them. Such cruises are carried out on board an oceanographic vessel because it is the only way to obtain data and samples from distant and/or deep locations. Obtaining a water sample from the sea surface is relatively easy, but retrieving the same sample from 30 meters deep is more challenging, and obtaining a sample from 1000 meters deep is very difficult and costly. Samples form the basis of data for many oceanographers, and since we cannot have a ship whenever we want, during the cruises we maximize sample collection. And here is where the problems begin. As you saw in the video posted in a previous entry, when a campaign starts, the first thing to do is to set up the laboratory or laboratories. Each specialist prepares their sample preparation systems. In our cruise, there are water samples that need to be acidified, others need to be filtered with different types of filters, and others require ultrafiltration. There are sediment samples that need to be frozen, others need to be stored in the refrigerator, others need to be sectioned, and so on. Together with the Diogenes syndrome of researchers with the potential samples, the growth of samples is... immense! The distant and hard-to-reach samples cost a lot - in effort, time, and money - to collect. Therefore, the worst thing that can happen is to realize, when analyzing them in land-based laboratories, that a sample is contaminated or the values obtained are not credible. Most problems start at the beginning of the sampling chain, usually from cleaning, maintaining the workplace, keeping the containers and instruments clean, and whether or not to touch the samples, sampling with gloves, using high-quality distilled water, and keeping filtration systems covered. But sample artifacts can be much more cumbersome. There are errors in sample labeling, sampling stations happen continuously, new water and sediment samples arrive, and the samples from the previous station have not finished being processed. On top of that, fatigue and possible seasickness add up. We work during the 24 hours and is the same the 11 AM that the 04 AM. Then, a nearly impossible-to-control variable comes into play: order! There is a false belief that scientists are disorganized people, the typical image of a person in a white coat and disheveled hair. However, organized scientists are much more efficient. Samples need to be labeled and ordered correctly. Leaving a sample out of the fridge or freezer for too long, or putting a sample that should go to the -80ºC freezer into the -20ºC one, can ruin a sample and hours of work and effort. A significant part of the work done in oceanographic cruises is summarized in ordering and labeling, or labeling and ordering samples appropriately. The samples remain on the ship and will not reach the land-based laboratory until several months after other missions have ended. Then, if the routine groundwork has been done correctly - sampling meticulously, processing with cleanliness, and preserving adequately - we can start analyzing the samples...

(by Antoni M. Calafat)

Bye, bye moorings! (03/08/2023)

Deploying a mooring to the seafloor is probably the most exciting and tense moment of our oceanographic cruises. A rope, a screw, a shackle, or a knot. The most minimum detail in the deployment of the instrumented line could mean losing the equipment and years of work. Concentration must be at its maximum, and attention to detail, constant.

Therefore, after more than 24 hours of work, we successfully deployed two moorings to study the evolution of currents, water masses, and particle flows. Alone, at depths of over a thousand meters, they must resist extreme conditions, collecting data until we release them in a year. Like a friend going on a trip, we said goodbye, knowing that we will see them again very soon. 

(by Marc Cerdà Domènech)

Exploring the seafloor of the Denmark Strait (04/08/2023)

Acoustic devices are also important allies in our cruise at the Denmark Strait. Among them, the multibeam echosounder, installed at the hull of the ship, is an acoustic system used to map and detect objects on the seafloor. It sends out multiple pulses of sound in a fan-shape that are reflected off the bottom and received back to the transducer installed under the ship. Then, the seafloor depth, or bathymetry, is computed by measuring the time it takes for the sound to travel to the seafloor, reflect and return to the ship. Onboard, we process this signal in order to translate these acoustic waves into depth measurements and create a map of the seafloor. Bathymetric surveys are normally carried out by following parallel lines on areas of interest, which are planned to get the maximum coverage of the seafloor.

During the last few days, we have mapped around 4,500 km ²  at the Denmark Strait! Meanwhile we also found the time to meet and talk about science and watch movies :)

(by Marta Arjona)

Current goes current comes (05/08/2023)

Investigating the oceanography of the Denmark Strait involves measuring the properties of the seawater and its displacements. We want to know how fast marine currents are and where they head to. To measure in place the intensity and direction of the water flow we use Acoustic Doppler Current Profilers (ADCPs). These devices rely on the Doppler effect (the difference in frequency emitted by a body depending on its velocity in relation to the receiver) to obtain an estimation of the current. Acoustic pulses are sent from the instrument and suspended particles and tiny animals reflect the sound and, assuming that these particles are drifting passively within the water flow, the Doppler displacement is due to the water movement and its velocity can be back-calculated. In fact, these instruments do not provide a single velocity measurement, but a bunch of them at increasing distances: a velocity profile.

In our cruise we use different ADCPs: attached to the mooring lines, two attached to the CTD and two more installed on the vessel’s hull. Seven in total!

(by Jacobo Martín de Nascimento)

Homemade Manual of an Oceanographic Cruise (06/08/2023)

"Life is problems and solving them." - Zorba the Greek (UK)

Oceanographic cruises are conceived months and years before their start. To carry out an oceanographic cruise, first, you need to secure funding, usually through a research project. The project justifies the research topic and the need for the cruise, specifies the study area and its characteristics (approximate duration, best time of the year or years for its execution, and the required technical resources). If the project is approved and the cruise is granted, then the chief scientist and/or the principal investigator of the project give the green light to a true course of bureaucratic obstacles. Neither Clarin nor Kafka imagined what this monster could reproduce! Certificates of occupational risks, medical certificates, certificates of..., purchasing tickets, hotel reservations (that fit within the ridiculous ministerial rates), sending the Cruise Plan specifying the tasks and technical needs of the cruise and the number of technicians participating. Then come meetings with potential participants and managers. The schedule often changes due to the needs of certain cruises (mainly biological researchs that need to sample at specific phenological moments of the studied species), or to adapt to the ship's management, etc. New meetings to adjust schedules, tasks, and date changes entail changes in personnel, both scientists and technicians. And the big day arrives. One day before the start of the cruise, you can board the oceanographic vessel, usually to set up the laboratories and allocate cabins. Typically, cabins are shared with another participant; only the Chief Scientist has a single-use cabin. The role of the Chief Scientist is crucial for the running of the cruise. He is an intermediary between the ship's Captain, the technicians operating the sampling instruments, and the scientists' interests. The Chief Scientist is the manager of the cruise, dividing laboratory spaces for different research groups (never enough and always poorly located!), assigning shifts to participants (everyone gets the worst or most boring one!), negotiating stations with scientists and the Captain, "feeding" scientists with samples and data (they are insatiable!), coordinating sampling operations with technicians (they always have to change a cable at the last moment!), and dialoguing with the Captain (there is always a toilet that doesn't work, or the need to enter a port on a different date!), taking care of people, equipment, ship, and having the final say. Oh, and as the Chief Scientist, writing the cruise report! Among the "non-standard" responsibilities of the Campaign Leader are trying to maintain a good atmosphere, overlooking clandestine parties and the students' dark circles, keeping spirits up during storms when everyone, including yourself, is half dead, and cursing the seas like Captain Haddock, trying to prevent the laboratories from becoming immense accumulations of garbage, enduring the scientist who already thinks we can return to port and the one who asks to repeat sampling stations (variability!) and chasing the scientists to each explain in the cruise report what they have done during the month they have been on board and being surprised at how the length of their explanation is inversely proportional to the number of samples collected! Mr. Wolf forever!

(by Antoni M. Calafat)

Neodymium… what? (07/08/2023)

CTD profile number 149 onboard RV Sarmiento de Gamboa!!! As you have seen before, the CTD is our most used instrument in this oceanographic cruise to define water masses in the Denmark Strait. This station is among the deepest ones with 2230 meters, that means… a lot of water sampling for Neodymium isotopes analyses!!

Neodymium (Nd) is an element that belongs to the Lanthanides group, also known as Rare Earth Elements. This group is located in the two disconnected rows of the periodic table that nobody ever pays attention to, but we sure do. The Neodymium isotopic composition (ε _Nd ) allows us to trace different water masses with different ε _Nd  values and study the mixing processes between them and the path they take, but also provides us information about water masses origin.

To do that we need 10L of seawater (a huge volume!)  that we preconcentrate in small cartridges. These cartridges retain the elements that we are interested in (Nd among them). This method allows us to process a lot of samples on board and go home with a small box of cartridges instead of hundreds of litres of seawater.

Nd also can be measured in microscopic fossils found in the sediment samples. This allows us to study the past water masses that were present in Denmark Strait. But we will have to wait until we are home to find these microfossils and the history they keep.

(by Sara Campderrós and Sara Espinosa)

Those tiny strangers (08/08/2023)

You might be used to brush your teeth with chlorophyll toothpaste, or to spend hours chewing chlorophyll gums. Then, you must know that chlorophyll is a pigment that allows photosynthetic organisms to absorb energy from the sun. To estimate the chlorophyll a concentration in seawater, its fluorescence is measured by a sensor attached to the CTD. Observing these profiles allows us to have a proxy for photosynthetic organism’s biomass in seawater such as algae.

Diatoms are unicellular algae that have been estimated to contribute around 20% of the total primary production on Earth. They belong to phytoplankton, that microscopic organisms that constitute the basis of marine food webs and are fundamental in oxygen production (right, not just terrestrial plants produce oxygen!) and climate regulation, through their capacity to fixate carbon dioxide and export it to bottom sediments. Diatoms have a siliceous skeleton, which make them look like true works of art! Due to this characteristic, they are tightly coupled with not just carbon but silica cycles. Thus, the quantification of diatom diversity and its elemental composition are important to understand their responses and implications for biogeochemical cycles in the future and changing ocean.

Like for particulate organic carbon (POC), lipid biomarker and total suspended matter studies, in this case we also need to filter water onboard. Depending on the type of diatoms analysis, we just need to sample some millilitres of water or to filter 10L per sample through different mesh sizes, which allow us discarding some organisms we are not interested in and concentrating the ones we are looking for. During the oceanographic cruise, we have already filtered more than 1200L of seawater just for this purpose. Although we will not stop working until the last day, we can tell that we can already go home fully satisfied!

(by Irene Llamas)

Maps, always the maps! (09/08/2023)

A big wall, a big map, a bunch of magnets and let the magic happen! Maps help us to think by providing a visual and spatial representation of complex data, to identify patterns and relationships, to establish connections between different elements and to make informed decisions. During the cruise, our big map in a small corner of the main lab has been like a Greek agora for us. The place where we have gathered in small and big groups to discuss, inspire and take decisions.

And meanwhile... after near three weeks sailing in Denmark Strait, we have seen again Iceland!

(by David Amblas)