MOSAiC: DLR is providing the world’s largest and longest polar research expedition with sharp radar vision from space

Press release from Deutsches Zentrum für Luft- und Raumfahrt

The Arctic is a vast expanse of ice and snow covering the Earth’s northernmost latitudes. Climate change has a strong, large-scale impact there, with ramifications that extend across the globe. A warming climate affects ice and water, the ocean currents, the atmosphere and the arctic ecosystem as a whole. Using their specialized expertise in sea ice monitoring, researchers at DLR’s Earth Observation Center (EOC) seek to better understand this interconnected system. In a new groundbreaking mission, they are about to improve the quality of satellite-based observations of sea-ice properties. Together with predictions of sea-ice drift, such measurements are expected to provide a unique set of data describing the status and change of sea-ice properties throughout the year, covering all Arctic seasons. This plan is complex and challenging. It thus requires interdisciplinary knowledge covering all the elements of the Arctic system. The EOC researchers have thus joined forces with an interdisciplinary team of renowned scientists from all over the world working together on one ambitious mission.

On October 4th 2019 (9:30 p.m. boat time) Polarstern reached the destination: The floe which we had chosen some days before with help of TerraSAR-X (Photo: AWI).
Subset of ALS quickview map with marked structures and roads. Red dashed line indicates the lead/shear zone. (Acquisition Date : 20th Oct 2019, Graphics: S. Hendricks, AWI)
Researcher from University of Bremen (G. Spreen) interpreting the TerraSAR-X image delivered in Near Real Time to the ship on the deck of Polarstern (Photo: S. Hendricks, AWI)

The campaign, known as the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), was launched in September 2019 as the largest ever campaign in the Arctic. It is coordinated by the Alfred Wegener Institute (AWI) and will study all aspects of the climate, a challenging task, given the complexity of the Arctic system. To face these multiple challenges, 19 countries are cooperating to make full use of their research potential. They have mandated their best polar researchers to form one interdisciplinary team to better understand the processes of climate change in the Arctic. AWI is providing Germany’s best known research vessel, the ice-breaker “Polarstern”. Over the course of one year, the ship will be home to 600 people, distributed over six consecutive legs. As the ship freezes in the arctic sea ice, it drifts across the central Arctic at about 7 km per day but with large variation, while the wind and currents might take it very close to the geographic North Pole. That undertaking is unprecedented. The majority of previous missions have explored the Arctic only in the summertime, when conditions are more bearable, instruments are easier to operate, the sea ice has more openings and the high north is more easily accessible. The MOSAiC mission is more ambitious. It does not avoid the challenges of the Arctic winter but it faces them.

The researchers onboard the Polarstern carry out measurements in extreme environmental conditions, when for several months the winter sun does not rise above the horizon and temperatures dip down to as low as -45°C. However, with today’s technology, the EOC researchers have a special asset: The German TerraSAR-X/TanDEM-X satellites are equipped with outstanding radar sensors (Synthetic Aperture Radar, SAR) which allow the researchers to see through the arctic darkness and through the clouds with unprecedented spatial and temporal resolution. Additional radar images from other satellites complement and improve that source of information. To streamline that huge amount of data, Dr. Suman Singha coordinates the acquisition of images from different satellites on behalf of DLR’s Remote Sensing Technology Institute (IMF). Scientists can thus monitor the status and change of sea ice properties throughout the whole project. While Polarstern now drifts through the frozen ocean, the IMF team watches the ship from above, and the TerraSAR-X/TanDEM-X mission is an important eye in the sky. The satellites host a high-precision sensor, the only type of sensor that can detect the structure of ice floes. After downlinking the data to the ground station in Neustrelitz, the images are processed immediately to deliver the information in Near Real Time (NRT) to the research vessel.

This information was and is much needed at Polarstern. Especially at the beginning of the expedition, when the challenge was to find a flow thick enough to carry heavy weight, and stable enough to protect against ice break-up and ridge formation. October 2nd was the day when the satellite sensor demonstrated its ability to deliver this information. With the help of the sensor, additional support of a helicopter, and the experienced eyes of the researchers and captain onboard, the IMF researchers finally guided the ship to the safest available floe. It was named ‘Fortress’ because it was destined to be a safe harbor and home for the researcher’s camp, including all of their delicate instruments.

TerraSAR-X/TanDEM-X ScanSAR view of the target ice floe ‘Fortress’, Floe size is approx. 1.5 x 2.5 km’. As of now a ‘quick-look’ product is delivered to the ship within 30 – 60 min after the image acquisition.

At the site, the team has now established hundreds of instruments surrounding the ship in a radius of up to 50 km. Yet, the atmosphere and the water are warming, and the ice is getting gradually thinner. The fragile layers are often breaking up and drifting apart. This is a risk to the safety of both the camp and the instruments. Monitoring the safety of the floe thus remains a constant challenge. Using the TerraSAR-X mission, DLR’s IMF team supported by DLR’s National Ground Segment at Neustrelitz (DFD), will therefore continuously watch the ‘Fortress’ and its surroundings from the sky on daily basis and inform the on-board researchers about any potential hazards. In fact, the Fortress floe has already broken into two larger and many small pieces during two storms. But thanks to continuous observation, the location of the main crack in the vicinity of the camp became immediately visible on the subsequent satellite image.

In future, in-situ and airborne measurements which are being carried out during this year round expedition, will be used by IMF researchers in collaboration with researchers from the University of Bremen in the framework of a joint project named ‘MOSAiCMicrowaveRS’ which is partly funded through the German Research Foundation (DFG).

TerraSAR-X radar satellite image from 17 Nov 2019, showing a major fracture zone from north to south though our floe (incl. the fortress) after a major storm event.

Date of publication: 9 Dec 2019

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