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By Rachel Flecker, Co-Chief Expedition 401

Tomorrow, after two months at sea aboard the JOIDES Resolution, Expedition 401 comes to an end as we dock in the port of Naples, Italy. Our expedition was all about the connection between the Atlantic and Mediterranean 8-4 million years ago. We know changes to this gateway profoundly changed the Mediterranean. The question is, did those changes also impact the Atlantic and what happened in the gateway itself?

Today the Gibraltar Strait is the Mediterranean-Atlantic gateway, but in the past there were at least two other connections: one to the south in Morocco and one to the north in Spain. These closed and as they did so, the saltiness of the Mediterranean increased dramatically leading to the accumulation of ~1.5 km of salt on the Mediterranean sea floor.

Expedition 401’s aim was to collect sediment cores that allow us to test two main hypotheses:

  1. that this change in Mediterranean salinity, changes the density of the water flowing out into the Atlantic, impacting the circulation of the global ocean.
  2. that the formation of a salt giant, changes the chemistry of the global ocean in ways that impact the carbon cycle

Both these physical and the chemical perturbations have the potential to drive climatic change globally.

The sediment cores we needed were buried hundreds of meters below the sea floor. It’s very unusual to be drilling for sediment archives of climate this deep because climate records need to be continuous, and deep drilling rarely results in recovering more than half of the sedimentary layers. However, as a consequence of new drilling technology and the expertise in scientific coring accumulated and honed over more than half a century by both the JR technical team and the drillers, Expedition 401 recovered unprecedentedly continuous core even from depths of more than 1km down. For example, the last core we recovered from our Mediterranean site was at 1070m and had 96% recovery.

What these complete records in the Atlantic show is that there is a clear response to changes in the Mediterranean-Atlantic gateway at the same time as the salt giant formed making it very likely that there was a physical change in ocean circulation (hypothesis 1). Hypothesis two will take a lot of detailed analytical work on the samples recovered to test.

But the big ship-board surprise actually came from our drilling just inside the Mediterranean to the east of Gibraltar. This area, the Alborán Sea, was thought to be the main Mediterranean-Atlantic gateway both immediately before and after the salt giant formed. The cores we recovered at this site, contain some of the most beautiful sediments we’ve ever seen – exquisitely laminated in a variety of colours.  This incredibly fine lamination requires very quiet, low energy conditions. This is not what we were expecting to see, because many of the models suggest that during salt giant formation, the Mediterranean Sea level dropped by hundreds of meters, causing major erosion of the margins including in the Alborán Basin. We were also anticipating a sedimentary signal caused by the catastrophic refilling of the Mediterranean, and we found no compelling evidence of that either.

All of this means that there are still lots of outstanding questions around the evolution of the Atlantic-Mediterranean corridor 8-4 million years ago. Luckily, Expedition 401 is part of a bigger Land-2-Sea drilling project, IMMAGE, that will drill the fossil gateways now preserved on land. So even though our ship-based drilling is coming to an end, we just starting to plan the next drilling expedition to Spain and Morocco.

What we’ve learned from Expedition 401 so far

Ocean Acidification

Between Storms and Science: Easter in the Labrador Sea (04.04.26–13.04.26)

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Between all the scientific work, we celebrated Easter on board, although the weather had other plans for us. Due to rough conditions, we weren’t able to carry out any CTD casts.

Photo: Sarah Tomae

Easter itself was spent in a mix of rest and small celebrations. Some of us enjoyed a long Easter breakfast with traditional Easter bread, while others took the opportunity to sleep in. In the evening, we gathered with both crew and scientists for a small celebration. The ship’s cook even organized a quiz, and those who answered correctly were rewarded with Easter chocolate.

The next day, the weather improved, and we began early with the recovery of K1, a 3,495-meter-long mooring in the middle of the Labrador Sea.

We joined the nautical officers on the bridge before sunrise to search for it. Fortunately, K1 has a floating buoy with a light, so we were able to spot it even in the dark. The actual recovery started at first light, and it began to snow while we were working.

Photo: Sarah Tomae, GEOMAR

Amid all the CTDs and mooring operations, there was also a personal highlight: my (Sarah’s) birthday. Although I’ve spent birthdays away from home before, this one felt especially unique, being so far out at sea, with only limited internet contact.

Normally, I work the 4-8 shift, but my incredibly kind shift team gave me the morning off. That meant I could sleep in and even find time to call family and friends back home. In the afternoon, I was surprised with my favourite cake, baked by Julia.

Our work continued with the mooring array at 53°N, which consists of seven moorings. So far, we have recovered five (K7, K8, K9, DSOW1 and DSOW2), and three of them have already been redeployed (K7, K8 and DSOW1,).

Deploying K7 turned out to be particularly tricky. On our first attempt, sea ice drifted toward us faster than expected, forcing us to recover nearly half of the mooring again. While the ship itself can handle drifting ice, deploying a mooring is much more delicate: a long cable with instruments and floats is released behind the ship before the anchor is dropped, allowing the system to sink into place.

Two days later, we tried again and this time, the deployment was successful.

Photo: Sarah Tomae

Afterwards, we moved closer to the sea ice, which was a highlight for many of us. Seeing the ice up close and even spotting a seal swimming nearby, made the experience unforgettable.

Photo: Sarah Tomae
Photo: Sascha Gniosdorz

Due to the continuing harsh weather, the decision was made to return to K1 and make use of an upcoming weather window for deployment the following day.

German:

Zwischen Stürmen und Wissenschaft: Ostern in der Labradorsee (04.04.26 – 13.04.26)

Zwischen all der wissenschaftlichen Arbeit haben wir Ostern an Bord gefeiert, auch wenn das Wetter andere Pläne für uns hatte. Aufgrund der rauen Bedingungen konnten wir keine CTD-Messungen durchführen (Messungen von Leitfähigkeit, Temperatur und Tiefe im Ozean).

Foto: Sarah Tomae

Ostern selbst war eine Mischung aus Erholung und kleinen Feierlichkeiten. Einige von uns genossen ein ausgedehntes Osterfrühstück mit traditionellem Osterbrot, während andere die Gelegenheit nutzten, etwas länger zu schlafen. Am Abend kamen Crew und Wissenschaftler*innen zu einer kleinen Feier zusammen. Der Koch organisierte sogar ein Quiz, und wer die Fragen richtig beantwortete, wurde mit Oster-Schokolade belohnt.

Am nächsten Tag besserte sich das Wetter, und wir begannen früh mit der Bergung von K1, einer 3.495 Meter langen Verankerung mitten in der Labradorsee. (Eine Verankerung ist eine lange, am Meeresboden befestigter Draht, der mit Instrumenten ausgestattet ist, um über längere Zeit Ozeandaten zu messen.)

Noch vor Sonnenaufgang gingen wir mit den nautischen Offizieren auf die Brücke, um nach ihr Ausschau zu halten. Glücklicherweise verfügt K1 über eine schwimmende Boje mit Licht, sodass wir sie bereits im Dunkeln entdecken konnten. Die eigentliche Bergung begann bei Tagesanbruch und es begann sogar zu schneien.

Foto: Sarah Tomae

Zwischen all den CTD-Einsätzen und Verankerungsarbeiten gab es auch ein persönliches Highlight: meinen (Sarahs) Geburtstag. Obwohl ich schon öfter Geburtstage fernab von zu Hause verbracht habe, war dieser besonders, so weit draußen auf dem Meer und mit nur eingeschränktem Internetkontakt.

Normalerweise arbeite ich in der 4-8 Uhr Schicht, aber mein unglaublich nettes Schichtteam hat mir den Morgendienst freigegeben. So konnte ich etwas länger schlafen und hatte sogar Zeit, mit Familie und Freunden zu Hause zu telefonieren. Am Nachmittag wurde ich dann noch mit meinem Lieblingskuchen überrascht, den Julia für mich gebacken hat.

Unsere Arbeit ging weiter mit dem Verankerungs-Array bei 53°, das aus sieben Verankerungen besteht. Bisher haben wir fünf geborgen (DSOW1, DSOW2, K7, K8 und K9), von denen drei bereits wieder ausgebracht wurden (DSOW1, K7 und K8).

Das Ausbringen von K7 erwies sich als besonders schwierig. Beim ersten Versuch trieb das Meereis schneller auf uns zu als erwartet, sodass wir fast die Hälfte der Verankerung wieder einholen mussten. Obwohl das Schiff selbst gut durch treibendes Eis navigieren kann, ist das Ausbringen einer Verankerung deutlich anspruchsvoller: Dabei wird ein langer Draht mit Messinstrumenten und Auftriebskörpern hinter dem Schiff ausgesetzt, bevor am Ende der Anker gelöst wird und das gesamte System absinkt.

Zwei Tage später versuchten wir es erneut, diesmal mit Erfolg.

Foto: Sarah Tomae

Anschließend fuhren wir näher an das Meereis heran, was für viele von uns ein besonderes Highlight war. Das Eis aus nächster Nähe zu sehen und sogar eine Robbe in der Nähe schwimmen zu beobachten, machte das Erlebnis unvergesslich.

Foto: Sarah Tomae
Foto: Sascha Gniosdorz

Aufgrund der weiterhin rauen Wetterbedingungen wurde schließlich entschieden, zu K1 zurückzukehren, um ein bevorstehendes Wetterfenster für die Ausbringung am nächsten Tag zu nutzen.

Between Storms and Science: Easter in the Labrador Sea (04.04.26–13.04.26)

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Humans Just Flew Around the Moon This Week. But Would Babies Born There Ever Truly Feel Gravity? Ask Jellyfish Babies.

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This week, NASA’s Artemis II crew made history by flying around the Moon and returning safely to Earth, the first human journey to the Moon’s vicinity in more than 50 years. It was a stunning reminder that humanity is no longer just dreaming about living beyond Earth. We are actively rehearsing for it.

And that leads to a much stranger, deeper question: even if one day we build skyscrapers on the Moon, raise families there, and turn space into a place to live, will babies born away from Earth develop a normal sense of gravity? Or will their bodies learn the universe differently?

To explore that question, NASA once turned to an unexpected stand-in for human babies: jellyfish babies. On the STS-40 mission, scientists sent thousands of tiny jellyfish polyps into space because jellyfish, like humans, rely on gravity-sensing structures to orient themselves. The experiment asked a simple but profound question: if a living body develops in microgravity, will it still know how to handle gravity later?

The answer was both fascinating and unsettling. The jellyfish developed in space in large numbers, but once back under Earth’s gravity, the ones that had developed in microgravity showed far more pulsing abnormalities than the Earth-grown controls. In other words, their bodies formed, but their sense of balance did not seem to work quite the same way.

That is why this old jellyfish experiment still matters today. Before we imagine lunar cities, schools, nurseries, and generations born off-world, we need to ask not only whether humans can survive in space, but whether developing there changes how the body understands something as basic as up, down, and movement. Jellyfish babies cannot tell us everything about human children, but they may have given us one of the first clues that life born beyond Earth might not come home unchanged.

Reference: https://nlsp.nasa.gov/view/lsdapub/lsda_experiment/0c10d660-6b12-573d-8c3b-e20e071aed3b

Image: GEOMAR, Sarah Uphoff

Humans Just Flew Around the Moon This Week. But Would Babies Born There Ever Truly Feel Gravity? Ask Jellyfish Babies.

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Ocean Acidification

First Week of Cruise MSM142 – Into the Labrador Sea

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After a slight delay of the Maria S. Merian caused by late-arriving containers our research cruise MSM142 finally got underway. By last Tuesday (24.03.2026), the full scientific team had arrived in Nuuk, the capital of Greenland, and the ship reached port on Wednesday (25.03.2026) morning. That same day, scientists and technicians moved on board and immediately began preparations, assembling and testing our instruments. Although the mornings on Wednesday and Thursday were grey and overcast, the afternoons cleared up beautifully. This gave us valuable time to organize equipment on deck and store empty boxes back into the containers before departure.

Foto: Julia Pelle

Given the forecast of harsh conditions outside the fjord, we carried out the mandatory safety drill while still in harbour. This included practicing emergency procedures and boarding the lifeboat. After completing border control, we were finally ready to leave Nuuk. We set sail on March 27th, heading into the Labrador Sea to begin our mission. Even before starting scientific operations, we tested the setup for deploying our gliders without releasing them during the transit out of the fjord. Once we reached open waters, we were met by high waves the following morning. For some on board, this was their first experience under such rough sea conditions. Seasickness quickly became a challenge for a few, while scientific work had to be temporarily postponed due to the strong winds and sea conditions. Together with the crew, we discussed how best to adapt our measurement plans to the given weather conditions. On March 29th, we were finally able to begin our scientific program with the first CTD deployment. A CTD is an instrument used to measure conductivity, temperature, and depth, which are key parameters for understanding ocean structure.  

Foto: Julia Pelle

During the following night, we continued with additional CTD stations and successfully recovered two moorings: DSOW 3 and DSOW 4, located south of Greenland. These moorings carry instruments at various depths that measure velocity, temperature, and salinity. DSOW 4 was redeployed on the same day, while DSOW 3 followed the next day. In addition, the bottles attached to the CTD’s rosette can be used to collect water samples from any desired depth. These samples can be used, for example, to determine the oxygen content, nutrient levels, and organic matter.

Foto: Julia Pelle

Both are part of the OSNAP array, a network of moorings spanning the subpolar North Atlantic. On these moorings are a few instruments, for example microcats which measure temperature, pressure and salinity.

We then conducted around 25 CTD stations spaced approximately 3 nautical miles apart across an Irminger ring identified from satellite data. This high-resolution sampling was necessary to capture the structure of an Irminger Ring, which had a radius of about 12 km wide.

Foto: Julia Pelle

The days leading up to April 2nd were marked by very rough weather conditions. Life on board became both challenging and, at times, unintentionally entertaining sliding chairs were not uncommon. During the night from April 1st to April 2nd, winds reached 11 Beaufort with gusts up to 65 knots, forcing us to pause our measurements. Fortunately, conditions improved by morning, allowing us to resume our work. As well as with the help of the crew we had to adapt to the harsh weather conditions to continue our scientific work. On the 3rd of April, we were able to deploy a few gliders and one float. An ocean glider is an autonomous underwater Vehicle, which you can steer remotely and send to different locations, while it is measuring oceanographic key parameters.

Foto: Julia Pelle

This research cruise focuses on understanding small-scale processes in the ocean and their connection to the spring bloom, an essential phase in marine ecosystem in subpolar regions. Despite the challenging start, we have already gathered valuable data and look forward to the weeks ahead in the Labrador Sea. 

First Week of Cruise MSM142 – Into the Labrador Sea

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