After 51 days at sea, we arrived back in Bremerhaven today in the morning hours. These have been eventful weeks; our work has taken us north along the eastern Fram Strait, back repeatedly to selected ice floes in the marginal ice zone. We have made a detour to the Aurora Vent Field and our last work areas were located along the east coast of Greenland. Behind us lie more than 5800 covered nautical miles and 38 days with fog. We worked through 119 scientific stations, kept polar bear watch for a total of 118 hours at various ice stations and emptied countless litres of coffee over the course of time. All in all, we can call the expedition a success, both from a scientific and a community point of view, and even though everyone is now looking forward to going home, we are already planning the first reunions to hear how the others are doing.

We spent the last days of our scientific program in the Greenlandic Scoresby Sund. Since difficult ice and weather conditions around the 79 North Glacier didn’t allow us to conduct our planned work there, we used the opportunity and recovered three moorings which were deployed in the Scoresby Sund four years ago. The gigantic icebergs and mountains of the fjord system over a thousand meters high were an impressing scenery for the end of our expedition! After we brought the last working device back on deck – a CTD measurement – the Arctic said goodbye to us in a very special way: all of a sudden a polar bear was swimming behind the stern of our ship and watched us curiously. Now our journey home has started. We’ll spend the remaining days packing and cleaning and will arrive back in Bremerhaven in the early hours of Wednesday morning.

An unusual encounter took place in the night to Wednesday, just before we entered the imposing scenery of the Scoresby Sund. In the middle of the Greenland Sea we met another German research vessel: Maria S. Merian, associated with the Leibniz-Institut für Ostseeforschung Warnemünde. At the current expedition MSM110, with Helmuth Thomas as cruise leader, researchers of Helmholtz-Zentrum hereon, Geesthacht, are guests on the Merian. Here they study the influence of glacial input and tipping points of the fjord systems. At our meeting, just a few miles off Greenland’s coast, the captains were able to talk from bridge to bridge and the ship’s horn was blown to send greetings before we both continued following our research assignments.

Sabine, Philipp and Arun have chosen a very special place on Polarstern for the atmospheric measurements. At the most outer tip of the bow crane we’ve installed a measuring system for aerosol particle fluxes that enables us to perform measurements directly above ice floes. Indeed, aerosols are only nanometer-sized particles and invisible for the human eye. Nevertheless, they have an important impact on the climate. Depending on their specific chemical and physical properties they are able to absorb light or contribute to the formation of clouds. The results of these measurements will produce a better understanding of the formation and deposition of different aerosol particles. Furthermore, these outcomes are supposed to reveal how the Arctic ice and water surfaces influence the atmospheric aerosol budget and the Arctic climate overall.

At the top of Polarstern’s monkey deck are our two microwave radiometers: With them, we – a small team from the University of Bremen and the University of Cologne – measure the radiation that the atmosphere emits as microwaves. The radiometer allows us to determine the temperature and humidity up to twelve kilometers above our heads. With these instruments and additional weather balloons we already could observe the inflow of warm, humid air masses from the south towards the Polarstern some time ago. They brought astounding warm temperatures of nearly 18 °C to the Arctic. However, the warm air was not quite close to the ground, it stayed cold for us and the warm jackets were still needed! Our radiometers don’t just look up: With the help of a new mirror design, we also look down at the sea ice. This is a similar perspective to that of satellites, which can observe the entire Arctic in one day. Our measurements here on site then help us to validate satellite data.

The deck crew actively supports the scientists by both providing advice and engaging in joint operations around the clock. Each morning the team (consisting of the bosun, a carpenter and eight ship mechanics) meets in the working alley to discuss the tasks of the day. The bosun and chief mate use their know-how to coordinate the task distribution to ensure all jobs are accomplished. Besides vessel maintenance the activities include anything from operating scientific devices, helping with the deployment of moorings and seaman duties. Flexibility and a knack for improvising in any situation allow the deck crew to contribute to the success of each Polarstern expedition.

For expeditions in the Arctic, weather plays an important role and also can be a limiting factor at times. Therefore, the meteorologist Patrick and weather technician Christian from the German Weather Service (DWD) are on board. One of their main tasks is to deliver a twice-a-day updated weather forecast, which helps the ship’s command and scientists for their planning and decision making. Even more dependent to the weather is the helicopter team and due to this more attendance towards the forecasts is needed. So far, the weather conditions were calm, which is not unusual during the summer time. However, with temperatures close to zero degrees, dense fog is a bothersome and frequent companion. Still, the members of the expedition have been able to enjoy already a couple of beautiful days with plenty of sunshine and those windows of very good weather conditions were used intensively for helicopter flight operations.

The study of melt ponds on the Arctic sea ice is an important part of our ice work of this expedition. Water existing due to melt processes causes decreasing reflection, which increases absorption of the ice surface – and ice surfaces are normally highly reflectively. An increasing absorption triggers higher temperatures, which in turn cause increasing melt. This phenomenon is called ice-albedo-feedback and plays a primary role in the fast warming of Arctic regions. To study this process we have our “Böötle” on bord, driven by Victor over the melt water areas on the ice floes. The Böötle is a floating measurement platform to quantify spectral characteristics and water depths of melt ponds on the Arctic sea ice. And obviously the ponds must get names; this one on the photo got the suitable name “Pond Nemo”.

On Monday evening, about 90 nautical miles off the coast of Greenland, we saw our first polar bear during this expedition. While a few of us just started dinner and mooring work was close to finishing at the working deck, the announcement came “There is a polar bear outside!” It was a mother with her young cub, which we could watch through our binoculars. With everyone safe on the ship and from safe distance, we could really enjoy this unique Arctic encounter.

Klaus is our ship’s doctor for this expedition and is our person to contact for medical questions and emergencies. Although it’s his first cruise on Polarstern, it is by far not his first travel to polar regions. Trained as an emergency surgeon, Klaus went for an overwintering to the Alfred Wegener Institute’s Antarctic Neumayer Station III in 2019. There he was not only the station’s doctor but also the head of the station and from time to time he wrote texts for the Neumayer blog. Taken by Antarctica, Klaus went south again in 2021 for a stay at the Kohnen Station further inland. And now he has swapped the station for the ship, going to the Arctic instead of Antarctica. First impression? Less additional duties, but way more patients. And he is happy to see the white frozen landscapes again, to which he already got used to.

Last Saturday we got the chance to deploy a new measurement platform in ice-covered conditions. The first deployment of the Triaxus – a device which is towed behind the ship while steaming at slow speed – was a great success. Beforehand, the instrument had been complemented by an ice protection system, so that it is now possible to deploy the Triaxus also in polar regions. Equipped with different sensors and with measurements on the Polarstern, which were going on in parallel, we were able to make a detailed study of the upper 150 metres of the water column along a 85 kilometres long transect. With upcoming fog and poor visibility conditions we had to recover the instrument after nine hours of continuous measurement. Now the Triaxus is back on deck, ready for the next deployment.

We intend to understand, how ice floes decay and melt during the summertime. In the last three days we therefore focused on measurements on three ice floes. Sensor buoys were installed, ice thickness surveys carried out and melt ponds represented another important study object. In addition, a series of holes were drilled through the up to two meters thick ice, so that observations of oceanic heat fluxes and of distributions of melt water underneath the sea ice could be obtained. The decay of the ice floes – being so typical of this time of year – occurred impressively fast during our work on the second floe, which split up into several pieces as a consequence of ocean swell penetrating the marginal ice zone on that day. Back onboard Polarstern we were able to see, that most of the floes surrounding us had experienced the same fate.

As already mentioned, we do not only take water samples and ice cores but also conduct air-based research on sea ice. As soon as the weather is favorable, Lena and Gunnar are flying with our Heli-Team over the ice floes to get more data to study the ice. They have cameras and a laser scanner installed on the helicopter to document the floes and to measure the structure and temperature of the sea ice. By flying with the helicopters, the team is getting the seldom chance to see the Polarstern from above. This photo for example was made during one of the test flights while we were on our way north towards the ice.

With a spectacular view of the 60 kilometers distant island of Spitsbergen three moorings were successfully recovered under partly challenging winds and ocean currents and a spare part was flown in by helicopter from the AWIPEV station in Ny Ålesund. In the nights before and after this, investigations of the water column continued using different instruments lowered from the ship. Nets were deployed, physical parameters like temperature and conductivity were recorded and we took water samples from different depths of the West Spitsbergen Current. This means night shifts also for my team, the nutrient team here on board. As soon as the CTD with the attached water sampler is back on deck, Sinhué, Annika and me, Klara, take water samples and analyze them to measure dissolved oxygen and nutrient concentrations in our lab. The aim of our work is to assess the distribution of nutrients between different water masses and to study how nutrients are delivered to the upper layers of the ocean as the Atlantic Water interacts with the marginal ice zone.

The first stations of our expedition are located in Fram Strait in the area of the West Spitsbergen Current –  a current transporting warm Atlantic water northwards into the Arctic. Since over twenty years we have been deploying and recovering moorings: sensors and sampling instruments attached to long ropes which are anchored to the seafloor by heavy weights. For the duration of two years the instruments take hourly measurements of temperature and current speeds of the water column and take water samples from different water depths. The moorings thus enable us to study data over the course of complete annual cycles– including the winter season, from which we still have only very few data in the polar regions due to the harsh environmental conditions.

Step by step, the workspaces and laboratories start to look like such. At home we packed boxes and wrote freight lists for several weeks, from the measuring instruments to the waterproof pen – everything must be brought to the ship. Now on-board the searching starts – in which container are our boxes? Where did I pack this one certain cable? Just within one day on sea, the empty rooms change to workable labs and the piles of cartons start to shrink. Now we have to set and calibrate the instruments, so hopefully we are all ready when we arrive at the first station in some days.

Here we go again: after a short stay in the shipyard, Polarstern is starting into the Arctic season and today also we scientists and technicians finally came on board. During the next seven weeks we will, among other things, investigate the interactions between ocean and glaciers off Greenland, conduct studies on sea ice melt north of Spitsbergen and deploy equipment for seismological measurements in the Aurora Vent field. However, during the transit to the north we first have to unpack, set up equipment in the laboratories and get used to the sea. In this app we will keep you up to date and report from our journey.