RV Maria S. Merian with dust-collecting buoy. Photo credits Karin Zonneveld/Gerard Versteegh

The aim of the expedition is to study sinking particles from sea surface towards the seafloor. The particular aim of the four NIOZ colleagues is to service dust-collecting buoys Carmen (off Cape Blanc, Mauritania) and Laura as well as high-resolution sediment-trap mooring M1 (both south of Cape Verde Islands) which have been collecting many particles, including Saharan dust, since we deployed them during RV Pelagia expedition 64PE482 in February 2021. In addition, we will be collecting dust with various instruments.
In the blog below you can follow our whereabouts and adventures at sea.
Another blog for this cruise is being kept on the MARUM website.

Link to marinetraffic website

Regular updates below this part, latest update on top:

5 December – Cup deformations
Per 10m water depth, the ambient pressure increases with 1bar. This is why we like to state that deep-sea research is much more difficult than space research; all our instruments need to be able to handle the enormous pressure differences. One way to visualize the pressure increase with depth is by sending styrofoam cups to the deep; all the air is pressed out of the foam and cups get small and rock hard. Since the pressure is in all directions, the cups maintain their shape and the decorations stay intact. These cups have been down to 2,500m = 250bar pressure. A pristine cup is shown for comparison.

Styrofoam cups get smaller when they are brought down to the deep

4 December - SIPA: Sinking Particles (and their fate)
The ultimate stop for the particles that we are studying is the seafloor, now some 1,500m below the ship. To sample the sediment stack that is piling up on the sea floor, there are several devices. Since we are most interested in recent sedimentation processes, we focus on the sea-floor surface, which can best be sampled using a so-called multicorer (MUC). This multi corer allows simultaneous sampling of N=12 50-cm long cores at the same time, which are then distributed amongst the different scientific disciplines. Here you see various team members of SIPA in their colourful overalls, sampling in their specific ways that are needed for the specific analyses to be carried out later in the lab. These analyses vary from microplastics to particle-size analysis, various kinds of organic matter and biomarkers, dinoflagellates, foraminifera, diatoms, coccolithophores etc.

MUC - Multicore harvesting on the deck of RV Maria S. Merian

The big advantage of the MUC is that the sediment-water interface stays intact inside the tube; this is what the seafloor looks like (although it is pretty dark at 1,500m). The sediments are greenish thanks to the amounts of organic material and despite the deposition of orange dust.

A piece of undisturbed sea-floor sampled in one of the MUC cores

3 December – dust forecasts
Nowadays there are excellent forecast models for mineral-dust emissions. One of those is Windy.com, which allows three-day forecasts. Four of these forecasts are combined in this clip to demonstrate that there indeed is a lot of dust in our study area off the Mauritanian coast at the moment. The buoy positions are indicated and the general ship’s track as well.
The animation nicely shows how there are several hotspots of dust emissions on the north-African continent. A few famous ones are in Chad, Algeria and on the west-African coast: in West-Sahara, Mauritania and Senegal. This model run also shows that by far not all dust travels westwards and it also clearly demonstrates how about 75% of the dust is deposited on the continent and only about 25% makes it out to sea (Shao et al., 2011 Aeolian Research 2, 181-204). Recent satellite studies estimate that every year about 182 million tons of dust are blown west from the northwest African continent (Yu et al., Remote Sensing of Environment 159, 232-249) across the Atlantic Ocean towards the Americas.

2 December - dust-fog
Next to all the marine-environmental consequences and potential of mineral dust, a very direct effect of all this material blowing through the atmosphere is a reduced visibility. Under normal conditions with clear skies, visibility at sea would be around 12-15nm (nautical miles, 1nm = 1.85km) but with this dust-fog it is reduced to less than ~3nm. Fortunately, RV Maria S. Merian's radar has little trouble 'seeing' through the fog.

A container ship suddenly pops up from the dust-fog

1 December - dust all around
As expected, the eastern Trades that picked up yesterday are carrying large amounts of Saharan dust! There is so much dust around that visibility is drastically hampered. The setting sun cannot penetrate through the dense layer of dust hanging over the ocean, such that it has disappeared long before it sank into the ocean as it normally would have.

A dusty sunset over the equatorial North Atlantic Ocean

With the high-volume dust collectors on top of the bridge (see post of 20 November) large volumes of air are pumped through filters. The effect is clear and the colour matches that of the atmosphere: Saharan dust!

Saharan dust as it appears on our filters

30 November - no dust without wind
The wind has picked quite nicely, which means that chances on Saharan dust are increasing. However, the strong winds (up to 19m/s ~Bft 8) also whip up the waves, as you can see in this YouTube clip. 

29 November –  how’s the weather?
Every day at exactly 10.30 UTC all over the Atlantic Ocean weather balloons are launched from ships to get an idea about the meteorological conditions in the atmosphere. These daily measurements are used by all kinds of met-offices in Europe and the data flow into computer models to make the weather predictions more accurate. The DWD – Deutsche Wetter Dienst installed a dedicated meteo-container on the Maria S. Merian to participate in this measuring program and the ship’s electronic officers launch a balloon every day.

28 November –  drifting traps
The theme of this cruise is SIPA – Sinking particles (and their fate in the water column) and one way to sample them is with so-called drifting traps; a set of open-top tubes that are suspended vertically and left to drift freely for a given set of time. In this case we let them ‘on their own’ for 36 hours.

The drifting traps are being recovered (the lids were not on when they were in the water....)

It is actually amazing how much material these devices collect in such a small amount of time. The green parts you see here are so-called faecal pellets; organic-material aggregates, or simply: zooplankton poo. Some white particles are individual zooplankton like copepods or pteropods.

Particles known as marine snow, faecal pellets and individual zooplankton on the bottom of one of the drifting-trap tubes

27 November –  recovery day
Today we had a busy program with the recovery of both a sediment-trap mooring and dust-collecting buoy Carmen. Thanks to great teamwork between Master Björn and his officers both on the bridge and in the dinghy, bosun Enno and his team on deck and the MARUM and NIOZ technicians, it all went very smoothly and successfully! Now it is time to see what samples the and data the instruments have collected….

Edible samples
Typically, the buoys are overgrown with gooseneck barnacles, which turn out to be considered a delicacy in e.g. Portugal. First cook Matthias took up the challenge and prepared a few of the barnacles. Like shrimps, one had to put a bit of effort in getting the edible parts out but we all tried and enjoyed the unexpected treat!

Gooseneck barnacles (German: Entenmuscheln) freshly harvested from the buoy

26 November - a dusty sunrise
Yesterday we had already observed a kind of hazy atmosphere. Where in Europe this haze is usually caused by small water droplets, in the area offshore the largest modern dust source in the world it is dust.
This dust can be most easily seen at both sunrise and sunset, when the sun's rays travel long distances through the atmosphere, where they encounter and are dispersed by many more of these dust particles relative to later during the day when the sun is high in the sky.
So, why are these sunrises and sunsets often accompanied by red colours? 
.....the answer my friend.... 

Sunrise over the equatorial northeast Atlantic Ocean

25 November – A geologist’s dream
In the early morning, about one hour before sunrise, we pass West of the island of La Palma, which has been suffering from volcanic eruptions for more than a month now. There were several options for the transit to our study area off Cape Blanc Mauritania and we agree that this was the best option; right past the side of the Cumbre Vieja volcano that is still actively producing hot lava.
For the geologists in the team a thing to be ticked off their bucket lists and for all on board simply a spectacular sight!

Hot lava streaming down the slope of Cumbre Vieja on La Palma [photo credit: Daan Eldering]

24 November – Land ahoy!
Right after breakfast we see some islands on the horizon: Madeira and its acompanying islets. This used to be a famous area for whale spotting, so we are keeping an extra eye out!

In the far distance one can discern the contours of the island Madeira
The ship's navigation system showing RV Maria S. Merian's ship track passing Madeira

23 November – a pot of gold?
With the rising sun on portside and rain on starboard, a beautiful rainbow can be seen from the aft deck. An excellent morning treat! We are tempted to ask Master Björn to steer towards it, to fetch the pot of gold.

Should we get to the end of the rainbow to fetch that pot of gold?

22 November - little stowaways
Since passing through the Bay of Biscaye, we have a few little stowaways on board; some finches and a robin. They are curious little fellows and one of them was caught by Daan checking out the books that are lying around in the hangar....

A little stowaway studying books in the hangar of RV Maria S. Merian [photo credit: Daan Eldering]

21 November - preparing the dust buoy
Although we will be sailing for almost a week before reaching the area offshore Cape Blanc, we are already making as many preparations as we can. Here you can see how Bob, inside RV Maria S. Merian's large hangar, checking the tower that we are going to exchange for the one that is presently standing on buoy Carmen. One new addition to the tower is the rain sampler, which we have yet to program.

NIOZ technician Bob preparing the tower of the dust collector that is going to be placed on buoy Carmen.

20 November - installing the dust collectors
On the highest deck of RV Maria S. Merian, we have installed two dust collectors, with which we will sample Saharan dust offshore NW Africa. These two blue 'mail boxes' each contain a vacuum-cleaner engine, which pumps air through an A4-sized paper. A wind vane makes sure that the samplers will switch off as soon as we have a tail-wind, so avoiding potential contamination from the ship's chimney. A rain sensor makes sure that the samplers do not suck water into the collectors. It will be a few days before we are allowed to sample the air in international waters.

NIOZ technician Bob and VU MSc student Daan installing the dust collectors on the top deck of RV Maria S. Merian

19 November - passing through the English Channel
On this screenshot one can clearly see how busy traffic is in the narrow channel between England and France, with large container vessels sailing North and South, ferries sailing East and West and fishing boats going in virtually all directions.

Screenshot of the Shipfinder app showing RV Maria S Merian in the English Channel

18 November - inslingeren / getting accustomed to the ship's movements

18 November - leaving Emden

Screenshot of the Shipfinder app showing both RVs Meteor and Maria S Merian entering/leaving Emden harbour

18 November - leaving Emden
After all the preparations it is now time to set sail for MSM104 - SIPA. We are scheduled to leave at 8.30 in the morning and --leave it to German punctuality-- right at that moment one of RV Maria S. Merian's sisterships, RV Meteor, is passing through Emden's sluice to take our spot in the harbour of Emden.

2 November - preparations: second outdoor test of the rain samplers

Testing the rain samplers with real rain

Three of the newly constructed rain samplers are being tested under 'real' conditions. Although the weather looks nice for the moment, rain is forecasted and we will leave the samplers 'alone' for three days to collect it.
On the buoys on the ocean the samplers will get their power from the solar-powered batteries. Here, on land, they get their power from a small battery inside the little yellow box. At the top of the fence you can spot the Vaisala weather sensor, which we use to calibrate the amount of rain that is registered by the rain sensors on the rain samplers as well as the amount of water collected by the samplers.
Let it rain!

18 October - preparations: first outdoor test of the rain samplers

Testing the water samplers with some artificial rain

After the lab tests were completed it is now time to feed the rain samplers some 'even-more-real' rain. Here you see Jan-berend and Bob testing one of the samplers with some artificial intense rain. In addition, we are trying to calibrate the sampler's rain sensor with the Vaisala meteosensor with which the buoys are equipped as well. The sampler responded well to the watering-can rainshower; the lid opened and water is being collected by one of the perspex tubes inside the sampler.

15 October - preparations: first test of the rain samplers

The water samplers are being tested inside the lab/sink

The rain collectors are ready to be tested and here you see Bob and Frank performing the first series of tests with artificial rain insde the lab. The rain sensor needs to be able to discern between sporadic spray and 'real rain'. It then needs to open the funnel and sample until either the rain has stopped or the bottle is full. This requires quite some sensors and programming lines but so far everything is working quite allright!

12 October - constructing a new instrument: the rain sampler

Empty bottles in a carrousel: the rain samplers are being constructed

During one of the last expeditions we have carried out below the Sahara dust plume, we have discovered the importance of Saharan dust being deposited with rain; one single rain shower resulted in almost 1g of dust per m²!. To quantify the amounts that are deposited throughout the year, NIOZ technicians have designed a rain sampler, which they are now constructing and testing. Here you see five carrousels with bottles that will be the core of these rain samplers. On the right-most set of bottles you can see little funnels that will rotate underneath a large funnel that lets in rain into the sampler. To be continued.... 

10 October - preparations - fixing the mast of the dust-collecting buoys

A spare instrument tower for one of the dust buoys is being prepared in the NIOZ workshop

To be able to service the dust-collecting buoys as swiftly as we can --shiptime is costly!-- we are already preparing a tower with all required instruments so that, at sea, we only have to exchange the buoys' tops. Here you get a peek inside the dust tower; the white box shows the carrousel on which the dust filters will be mounted.