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Die physikalische Ozeanographie beschäftigt sich in großen Teilen mit Meeresströmungen: wo sie genau verlaufen, wie stark sie sind und ob sie sich verändern. Im vorherigen Blogeintrag ging es um die Verankerungen, die unter anderem Strömungsgeschwindigkeiten messen können. Diese Methode, also ein Messgerät an einem festen Punkt zu installieren und aufzuzeichnen, was vorbeifließt, nennt man Euler Methode. Der andere Ansatzpunkt – die Lagrange Methode – beruht darauf ein Messgerät ins Wasser auszusetzen, es mit der Strömung treiben zu lassen und seine Bahn zu verfolgen.
Die Idee ein Objekt mit der Strömung driften zu lassen, gibt es schon lange. Georg Neumayer kam auf die Idee Kapitänen auf ihren Reisen eine Flaschenpost mitzugeben, die an bestimmten Orten ins Wasser geworfen werden sollten. In der Flasche befand sich ein Brief, der die Finder bat sich zu melden und Fundort und -zeit zu übermitteln. Die erste dieser Flaschen ging am 14.Juli 1864 vom Schiff „Norfolk“ in der Nähe von Kap Hoorn zu Wasser. Erst drei Jahre später wurde sie an der Südküste Australiens wiedergefunden.
Ein unfreiwilliger Einsatz solcher sogenannten Drifter geschah 1992 bei einem Unfall eines Containerschiffs im Nordpazifik. Das Schiff, das von Hongkong auf dem Weg in die USA war, verlor in einem Sturm mehrere Container. Einer von ihnen hatte Badewannen-Tiere aus Plastik geladen: Quietscheenten, Biber, Schildkröten und Frösche. Geschätzte 29000 dieser Plastiktiere schwammen also plötzlich im Meer und wurden in den kommenden Jahren von Spaziergängen an zahlreichen Stränden gefunden. Zahlreiche Funde konnten auf Hawaii und in Australien vermeldet werden, einige schafften es sogar zur Westküste der USA sowie nach Schottland und England. Wahrscheinlich waren sie durch die Beringstraße nordwärts ins Nordpolarmeer bis nach Grönland in den Nordatlantik gedriftet. So wurde der Containerunfall zu einem Glücksfall für die Wissenschaft.
Die Drifter, die heutzutage eingesetzt werden, können schon ein bisschen mehr als Neumayers Flaschenpost und die verunglückten Plastiktiere. Bei den letzteren beiden, war nicht ersichtlich, welchen Weg sie zwischen Start- und Endpunkt zurückgelegt hatten. Moderne Drifter senden ihre exakten Messdaten automatisch über Satelliten an Datenzentren und machen so die annähernd simultane Beobachtung ihrer Wege möglich.
Auf dieser Fahrt haben wir auch Drifter dabei: gebaut vom Helmholtz Zentrum Hereon in Geestacht. Wissenschaftler*innen vom Hereon haben an einem Prototyp gearbeitet, der weniger Plastik enthalten soll. Jetzt besteht er aus einem Einwegglas, in dem sich Batterien und Software befinden und das erstaunliche Ähnlichkeit zu Neumayers Flaschenpost Idee zeigt. Für zusätzlichen Auftrieb und um das Glas aufrecht in der Wassersäule zu halten, befindet sich ein breiter Holzring am oberen Teil des Glases. Am Ende wird noch ein Aluminiumsegel an die Unterseite des Drifters gehängt, um ihn stabil in der Wassersäule zu halten. Einige der Drifter sammeln zusätzlich zu Positionsinformationen auch Daten über Druck und Temperatur der Luft sowie Wassertemperatur.
Nachdem wir jetzt einige Wochen mit der Vorbereitung der Drifter und dem Zusammenbauen der Einzelteile verbracht haben, sind nun die ersten Drifter zu Wasser gelassen worden. Ob sie zuverlässig funktionieren, wird sich in den nächsten Tagen zeigen. Schon jetzt kann man einige der Drifter online verfolgen. Schaut einfach hier auf der Webseite von Beluga vorbei.
Drifter in a bottle
Physical oceanography is largely concerned with ocean currents: where they go, how strong they are and whether they change. The previous blog post was about the moorings, which can measure, among other things, flow velocities. This method of installing a measuring device at a fixed point and recording what passes by is called the Euler method. The other approach – the Lagrange method – is based on placing a measuring instrument in the water, letting it drift with the current and tracking its trajectory.
The idea of letting an object drift with the current has been around for a long time. Georg Neumayer came up with the idea of giving captains a message in a bottle on their journeys, which should be thrown into the water at certain places. The message was a letter asking the finders to come forward and provide the location and time of the discovery. The first of these bottles was launched on 14 July 1864 from the ship “Norfolk” near Cape Hoorn. It was only three years later that it was found on the south coast of Australia.
An involuntary use of such so-called drifters occurred in 1992 in a container ship accident in the North Pacific. The ship, which was on its way from Hong Kong to the United States, lost several containers in a storm. One of them had loaded bathtub animals made of plastic: squeaky ducks, beavers, turtles and frogs. An estimated 29,000 of these plastic animals suddenly swam in the ocean and were found during walks on numerous beaches in the years to come. Countless finds have been reported in Hawaii and Australia, some even made it to the west coast of the United States, as well as to Scotland and England. They probably drifted north through the Bering Strait into the Arctic Ocean as far as Greenland into the North Atlantic. So the container accident became a stroke of luck for science.
The drifters that are used today can already do a little more than Neumayer’s bottles and the plastic animals. For the latter two, it was not clear which way they had travelled between the starting point and the end point. Modern drifters send their precise measurement data automatically via satellites to data centers, making it possible to observe their paths almost in near real time.
On this trip we also have Drifters with us: built by the Helmholtz Centre Hereon in Geestacht. Scientists from Hereon have been working on a prototype that is supposed to contain less plastic. Now it consists of a big glass containing batteries and software and shows the astonishing resemblance to Neumayer’s bottle post idea. For additional buoyancy and to keep the glass upright in the water column, there is a wide wooden ring at the top of the glass. At the end, an aluminum sail is attached to the bottom of the drifter to keep it stable in the water column. In addition to position information, some of the drifters also collect data on air pressure and temperature as well as water temperature.
After we have spent a few weeks preparing the drifters and assembling the parts, the first drifters have now been launched. Whether they function reliably will be revealed in the coming days. You can already track some of the drifters online. Just check out the website of Beluga here.
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.
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.
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.
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.
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).
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.
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.
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.
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)
Ocean Acidification
Humans Just Flew Around the Moon This Week. But Would Babies Born There Ever Truly Feel Gravity? Ask Jellyfish Babies.
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
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.
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.
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.
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.
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.
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.
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