- Successful flyover with research plane Polar 6
- Substantial melting in regime 1 in the ice-edge zone
- Oceanographic programme records the regimes on different scales
Flyover with the IceBird plane Polar 6
At the end of the work at the third ice station northeast of Greenland, the CONTRASTS team got to enjoy a special highlight: As the first flight in the IceBird summer aircraft campaign, the AWI’s polar research plane Polar 6 flew over and surveyed the ice floe (Figure 1). What had been planned for a long time but considered unlikely due to the expected weather conditions was a success: In the morning, Polar 6, with sea-ice measuring instruments on board, took off from Station Nord (Greenland), reaching the current station of the CONTRASTS expedition at 11:00 UTC (= ship’s time). Shortly beforehand, everyone on board was informed that the plane would pass on the ship’s starboard side in a few minutes during its measurement flight. As a result, nearly everyone came out on deck or on the sea ice. The flyovers with the EM-Bird, which was towed just 15 m above the sea ice under the aircraft, were quite a sight to see. After approaching from the west, two flyovers were made with the EM-Bird to measure the thickness of the sea ice. The EM-Bird was then hauled back up to its bay in the fuselage and three more flights were made over the ice floe at different altitudes, this time using a laser scanner that measures the surface heights of the ice and meltponds.
Figure 1: The Polar 6 research plane passes over RV Polarstern during a measurement flight as part of the IceBird summer 2025 campaign (22 July 2025). The plane is towing the EM-Bird (behind the ship, not visible) to measure ice thickness. (Photo: Alfred-Wegener-Institut / Evgenii Salganik)
The day was particularly successful because the team on board managed to carry out flights with the helicopter and a drone alike, while also taking measurements on the surface of the floe. Dr Thomas Krumpen, co-expedition leader on RV Polarstern and heavily involved in the aircraft measurements, couldn’t be happier: “We were very fortunate with the weather today, and everything went perfectly. This is the icing on the cake after the successful first few weeks of CONTRASTS and a great start to the IceBird campaign. Congratulations to everyone involved on the ship, in the aircraft, and especially on land.” The result of their combined efforts: a new, unique dataset on ice thickness and surface properties. Even though no further flights with the polar aircraft were possible in the following days due to the weather around Station Nord, both teams hope that further flights over the CONTRASTS floes will still be possible. This would mean the dataset could be expanded to include other ice regimes. In addition, the aerial measurements capture sea-ice variability on greater scales than can be done from RV Polarstern.
Transit with a visit from a polar bear
On 22 July 2025, work at the third ice station was completed, which means that all three stations – one per ice regime – have now been surveyed and equipped with sensors. As Dr Marcel Nicolaus (AWI), expedition leader of the CONTRASTS expedition, sums up (Figure 2):
Having found the three different regimes was already a great success. Even though we’d always planned for it, it wasn’t clear until the very end whether we would succeed in finding three main ice floes that they would show the expected contrasts. Now we’re delighted to see substantial contrasts in the sea-ice properties. This is a major step forward, and I’m very excited to see what the ice floes will look like after two weeks and then after four weeks of melting.
In fact, there will be three rounds in which each ice floe (together with the atmosphere above it and the ocean below) will be measured (Figure 3). In between, autonomous systems will continue to take measurements and constantly transmit data and images back home and to RV Polarstern. The experts expect to find that the atmosphere, sea ice, and ocean vary and change significantly. “In the best-case scenario, we will arrive at Station 1 in the third round just in time to take new readings and recover all the equipment before the ice floe completely disintegrates. I’m less concerned about Stations 2 and 3,” says Marcel Nicolaus.
During the transit from Station 3 to Station 1 (approx. 300 nm / 540 km), the first few days were used to tidy up the ship. Due to the constant work done at the various stations, there were plenty of empty crates standing around – which had contained equipment that was now on the ice. Further, all the tools needed routine maintenance and preparation for the next round. The team also found time for a barbecue on deck.
At 10:40 a.m. on 23 July 2025, the clean-up work was interrupted by the loudspeaker: “This is an announcement for everyone on board. We are about to pass a polar bear on the starboard side, approximately 50 metres from the ship.” Nearly everyone on board rushed to the deck to catch a glimpse of the first polar bear seen up close during the expedition (Figure 4). A real highlight! The research teams were very happy about the polar bear sightings, especially in beautiful sunshine. In contrast, when working on the ice, they’re all happy to do without these visits.
Figure 2: Overview of the conditions at the three stations of the CONTRASTS expedition. The images show photos from the camera buoys installed at each station. Each buoy is equipped with two cameras, one above the sea ice and one below. (Figure: Alfred Wegener Institute)
Figure 3: Previous route of the CONTRASTS expedition (as of 27 July 2025). The route taken by RV Polarstern is shown in blue. The green lines show the drift of the stations during the RV Polarstern’s absence. Red dots indicate the stations visited so far and red circles indicate future stations, whose position depends on the ice drift and is shown for illustrative purposes only. The sea-ice concentration on 26 July 2025 is shown in the background. (Figure: Alfred Wegener Institute / Marcel Nicolaus)
Figure 4: A polar bear along the route of the CONTRASTS expedition on 23 July 2025. (Photo: Alfred Wegener Institute / Marcel Nicolaus)
The return to ice floe 1 was very exciting, with a mixture of looking forward to returning and concern that the ice floe might be melting too quickly or drifting into the ice-edge zone. Satellite images showed that, although it was still almost 100 km from the open ocean, the ice floe had drifted more than 120 km south in the last two weeks – not ideal conditions. At the same time, the cameras and data from the ice floe showed that parts of the thin ice had already melted significantly. On the other hand, as the scientists on board all agreed:
That’s why we’re here. We want to watch the sea ice melt in summer and better understand how it happens and what the ocean and atmosphere contribute. We can only do so by taking a risk and when the melting actually takes place.
This also meant they had to decide which instruments to leave on the ice and which ones to retrieve. After all, many of the devices store their data locally, which means they have to be retrieved to get at their data. On the other hand, if the devices aren’t left behind, there definitely won’t be any new data.
On board: The ocean team
The goal of the expedition is to gather information on three different ice regimes. But what about the ocean below this sea ice? Are there also different ‘ocean’ regimes? This is what the ocean research team is investigating during this expedition. In addition to the regular CTD (conductivity, temperature and depth) programme, specific instrumentation is being deployed below the sea ice to capture the variations among the three sites. The ocean team is exploring the contrasting regimes on scales ranging from centimetres to kilometres. Several instruments, ADCPs (Acoustic Doppler Current Profiler) mini-moorings and eddy-covariance systems, are deployed under the sea ice to capture the centimetre-scale, under-ice turbulence. Figure 5 shows the deployment of one ADCP on the second regime floe. In total, five ADCPs and four mini-moorings were deployed around a pressure ridge to better understand its influence on the under-ice turbulence field. As Dr Zoe Koenig (UiT, Norges arktiske universitet, Tromsø, Norway), head of the ocean research team on board, says: “Given the differences in the coarseness of the underside of the sea ice, we expect to find differences in the under-ice turbulence between the different sea ice regimes.”
As sea ice ages, its underside can become coarser due to deformation. Thus, multi-year ice could generate more under-ice turbulence than first-year ice. This has consequences on the heat fluxes from the ocean to the sea ice, but also on the ecosystems, with variations in the nutrient fluxes for example. On the third ice floe, home to the oldest sea ice, an eddy covariance system was deployed by Eun Yae Son (Hokkaido University, Japan) to observe turbulent heat fluxes from the ocean during the melting season.
The ocean team is also investigating the differences in under-ice temperature, salinity, and light at spatial scales of tens of metres at each station, with a particular focus on areas near leads and meltponds. Lastly, a distributed network of autonomous buoy was deployed at horizontal scales of several kilometres around the main floe to document the mesoscale activity: oceanic eddies. The buoys are equipped with temperature and salinity sensors that can measure down to 100m. In addition to these buoys, a host of temperature and salinity profiles are being collected by Ke-Hsien Fu (National Academy of Marine Research, Taiwan) using an XCTD (expendable conductivity, temperature and depth) profiling system (Figure 4) within a 30km radius around the main floe (Figure 6).
Figure 5: A surface buoy mounted with a downward-looking ADCP was deployed on the second regime floe. (Photo: National Academy of Marine Research, Taiwan / Ke-HSien Fu)
Figure 6: An XCTD was deployed at the edge of ice floe. (Photo: National Academy of Marine Research, Taiwan / Ke-HSien Fu)
The next step for the ocean team: collecting the data gathered the instruments since the last visits to the floes, so that three different regimes can subsequently be described from an oceanographic standpoint.
Contact
Dr. Zoe Koenig (UIT Norwegens Arktische Universität, Tromsø, Norwegen)
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