Polarstern’s tour explores a giant calf iceberg

About two weeks ago, a huge iceberg erupted from the Antarctic ice sheet. As the only research vessel nearby, the Polarstern took the opportunity to enter the area between the iceberg and the Brunt Ice Shelf. Early images from the seabed show a remarkable level of biodiversity in an area that has been covered with thick ice for decades. The collected sediment samples are expected to provide more detailed insights into the ecosystem, and geochemical analysis of the collected water samples will allow decisions to be made regarding nutrient content and marine currents.

People around the world are enthralled by satellite imagery of the giant iceberg known as the A74, whose calves came from the Antarctic Brunt Ice Shelf on February 26, 2021; with an area of ​​1270 square kilometers, the iceberg is twice the size of Berlin. The German research icebreaker Polarstern is the only research vessel on site, and has succeeded in entering the gap between the iceberg and the edge of the shelf, to study the bottom of the a sea that has been covered with hundreds of meters of ice for decades. Experts from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) and their international partners came to the scene shortly after the calf birth event. The scientists on board are delighted with the once-in-a-lifetime photographs and sediment samples from the seabed, not to mention the geochemical measurements of the water column above it. Gale force winds had kept the Polarstern from reaching the area, but over the weekend (13/14 March 2021), more favorable weather forced the captain to provide a green light for a tour of the iceberg and explore the surrounding area. .

German Federal Research Minister Anja Karliczek reaffirms the importance of this mission, which is made possible through the institutional funding of the AWI by the Federal Ministry of Education and Research, as follows: “This is a unique opportunity for researchers on board Polarstern explore Antarctic Ice Sheet I am grateful to the Polarstern team for accepting the hardships associated with it and also the dangers. Polar research contributes significantly to a better understanding and anticipation of climate change and its impact on our land. We need this knowledge in order to be able to take effective side effects against climate change. The effects of climate change in Antarctica, among others, are worrying. “

This on-site research is essential to understand the processes by which calf birth events move. While this offers vital small photos, it is rarely possible to be nearby when an area is free of ice and first exposed to sunlight. An iceberg of this size only gives birth about once every 10 years in Antarctica. The smaller peers break free more often: snow falls and condenses in thick layers of ice, which slide slowly across the continent towards the sea. . Ice tongues, known as ice shelves, float on the ocean instead of resting on dry land, and finally a calf when an internal ice force makes the connection to the unstable glaciers.

So far, climate change has warmed particularly West Antarctica; global temperature has not yet affected Eastern Antarctica, i.e., the Polarstern’s conventional research region. However, climate models predict that, during this century, air temperatures will rise over the East Antarctic Weddell Ocean, adversely affecting sea ice. At the same time, such changes could fundamentally transform the irrigation: so far, a stable surface has kept moderately warm water from reaching the ice shelf. If sea ice is smaller and thinner, so less salt is released into the water column, the surface may become unstable, and the warmer water may be lets through it melt the shelf from below. In addition, a warmer feeling may result in an iceberg giving birth more often. Antarctica is currently losing ice mass at a higher rate than it was before 2000, as AWI experts have observed.

To create simulations, researchers need data from the regions in question – and collected not just once, but consistently over extended timeframes. Accordingly, the Alfred Wegener Institute has made regular Polarstern trips to the Weddell Antarctic Sea since the 1980s. In this regard, the seabed, ocean, ice and atmosphere are studied – with different areas of focus, depending on the individual trip. “It is very fortunate that we were able to respond flexibly and study the calf incident at the Brunt Ice Shelf in such detail,” said Dr Hartmut Hellmer, an AWI physicist and tour leader. The planned area lies in the southeast of the Weddell Sea, so it was nearby. That being said, I am even more pleased that we have successfully replaced several moors, which continue to record basic data on temperature, salinity, and normal ocean directions and distances once we are on. leave. This data forms the basis of our simulations of how the ice sheet will respond to climate change. As a result, we can say with a higher degree of certainty how fast sea levels will rise in the future – and we will provide good data to the political community and society at large for its making decisions about the necessary climate change adaptation measures, “Hellmer explains.

The experts found that, despite being permanently covered with ice for decades, the seabed has impressive biodiversity. The research team saw at deep sea a number of organisms that had settled on rocks of various sizes, surrounded by a silty landscape. The rocks come from the Antarctic continent and glaciers carry them to the ocean. Most of the organisms on them are seeds. It is unclear whether they eat algal residues, or on organic particles carried by the ice. The experts also found several non-native species such as sea cucumbers, starfish, various molluscs, at least five species of fish and two species of squid. The team at deep sea photographed and filmed this amazing ecosystem with many species for the first time using the OFOBS (Ocean Shirt Observation System and Bathymetry). Because the camera platform is tucked under the vessel on a long cable, the researchers had to wait for the calf birth event before they could explore the seabed that was not easy to accomplish. In the future, new technologies such as automated underwater robots will be used to study such habitats.

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