A huge iceberg broke off the Antarctic ice sheet about two weeks ago. The Polarstern is the only research ship on site and has used the opportunity to sail into the gap between the Brunt Ice Shelf and the iceberg.
The first images of the sea floor show an astonishing diversity of life in a region that was covered by thick ice for decades. Sediment samples are now supposed to provide more precise information about the ecosystem and the geochemical analysis of the water samples obtained allows conclusions to be drawn about nutrient content and water currents.
The world is watching satellite images of the giant iceberg called A74, which broke off the Brunt Ice Shelf in Antarctica on February 26, 2021; At 1270 square kilometers, the iceberg is about twice the size of Berlin. The German research icebreaker Polarstern is the only research ship on site and has succeeded in penetrating the gap between the edge of the ice shelf and the iceberg in order to explore the seabed, which had been hidden under hundreds of meters of ice for decades.
The researchers from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) and their international partners reached the area shortly after the demolition. Unique recordings of the seabed, sediment samples from the seabed and geochemical measurements of the water column above ensure enthusiasm on board.
Federal Research Minister Anja Karliczek underlines 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: “It is a unique opportunity offered to researchers on the Polarstern on the Antarctic Ice Sheet. I am grateful to the crew of the Polarstern for taking on the associated hardships and risks. Polar research makes a decisive contribution to better understanding and foreseeing climate change and its consequences for our earth. We need this knowledge in order to be able to take effective countermeasures against climate change. The effects of climate change in Antarctica, among others, are worrying. ”
This on-site research is essential to understand the processes involved in a massive iceberg break. They are an important snapshot, but it is seldom possible to be there when an area becomes ice-free for the first time and comes into contact with sunlight. Icebergs that big only break off every 10 years in Antarctica.
Smaller icebergs are released more often: Snow falls, is compressed into thick layers of ice and these then slowly slide down the continent towards the sea. Foothills of the ice float on the ocean as a so-called ice shelf, so they no longer lie on solid ground and ultimately calve when their connection to the glaciers becomes unstable due to the ice that is pushed in further.
So far, climate change has mainly warmed West Antarctica, but the global temperature increase has not yet affected East Antarctica and thus the current research area of the Polarstern. However, climate models predict that the air temperature in the eastern Antarctic Weddell Sea will also rise over the course of this century, with negative effects on the sea ice. Such changes would then lead to fundamental changes in hydrography: So far, a stable front has prevented relatively warm water from reaching the ice shelf. If thinner and less sea ice releases less salt into the water column, this front could become unstable and the warmer water would melt the ice shelf from below. In addition, a warmer atmosphere could make the icebergs calve faster.
In order to be able to make such model calculations at all, data from the regions concerned are required – and not just once, but over long periods of time. The Alfred Wegener Institute has therefore been conducting Polarstern expeditions to the Antarctic Weddell Sea since the 1980s.
The sea floor, ocean, ice and atmosphere are the subject of research – each with a different focus on the expedition. “It is a stroke of luck that we react flexibly and that we were able to research the demolition process on the Brunt Ice Shelf in such detail,” says Dr. Hartmut Hellmer, physical oceanographer at the AWI and leader of the expedition. The planned research area extends to the southeastern Weddell Sea and was therefore close by anyway.
“I am even happier, that we have successfully exchanged a large number of anchorages which, even in our absence, record elementary data on temperature, salinity, flow direction and speed. They form the basis for our model calculations on how the ice sheets will react to climate change. In this way, we can predict with greater certainty how quickly the sea level will rise in the future – and provide politicians and society with reliable data in order to take the necessary measures to adapt to climate change, ”says Hartmut Hellmer.
The diversity of life on the sea floor was great despite the years of continuous ice cover. The deep-sea research team observed numerous animals stuck on stones of different sizes, surrounded by a muddy landscape. The stones come from the Antarctic continent and are transported into the sea with the glaciers. Most of these organisms are filter feeders. Whether they feed largely on algae remains or on organic particles that are transported with the ice remains to be clarified. Some mobile species were also discovered such as sea cucumbers, starfish, various molluscs, as well as at least five species of fish and two species of squid. The deep-sea team photographed and filmed this surprisingly species-rich ecosystem for the first time with the help of the OFOBS (Ocean Floor Observation and Bathymetry System). The camera platform is towed from the ship on a long wire and the researchers have therefore been dependent on the ice breaking off in order to explore the previously inaccessible seabed. In the future, new technologies such as autonomous underwater robotics will be used to explore such habitats.
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