To date, climate change has especially warmed West Antarctica; the global temperature rise hasn’t yet affected East Antarctica, i.e., the Polarstern’s current research region. However, climate models predict that, in the course of this century, the air temperature will also rise over the East Antarctic Weddell Sea, negatively affecting the sea ice. In turn, such changes could produce fundamental transformations of the hydrography: to date, a stable front has kept comparatively warm water from reaching the ice shelf. If there is less and thinner sea ice, and therefore less salt is released into the water column, that front could become unstable, and the warmer water it lets through could melt the shelf from below. In addition, a warmer atmosphere could mean that icebergs calve more frequently. The Antarctic is currently losing ice mass at a higher rate than before 2000, as the AWI experts have observed.
In order to create simulations, researchers need data from the regions in question – and gathered not just once, but consistently over extended timeframes. Accordingly, the Alfred Wegener Institute has conducted regular Polarstern expeditions to the Antarctic Weddell Sea since the 1980s. In this regard, the seafloor, ocean, ice and atmosphere are investigated – with different focus areas, depending on the respective expedition. “It’s extremely fortunate that we were able to respond flexibly and explore the calving event at the Brunt Ice Shelf in such detail,” says Dr Hartmut Hellmer, a physical oceanographer at the AWI and head of the expedition. The planned region lies in the southeast Weddell Sea, so it was already close by. “That being said, I’m even happier that we successfully replaced a number of moorings, which will continue to record elementary data on temperature, salinity, and ocean current directions and speeds once we’ve left. This data forms the basis for 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 quickly the sea level will rise in the future – and provide the political community and society at large with sound data for making decisions on necessary climate change adaptation measures,” Hellmer explains.
The experts found that, despite being permanently covered with ice for decades, the seafloor is home to impressive biodiversity. The deep-sea research team observed numerous organisms that had settled on stones of various sizes, surrounded by a silty landscape. The stones hail from the Antarctic continent and are transported to the ocean by glaciers. The majority of the organisms on them are filterers. Whether they chiefly feed on algal remains, or on organic particles transported with the ice, remains unclear. The experts also found a number of non-sessile species like sea cucumbers, sea stars, various molluscs, at least five fish species and two squid species. The deep-sea team photographed and filmed this surprisingly species-rich ecosystem for the first time using the OFOBS (Ocean Floor Observation and Bathymetry System). Since the camera platform is towed below the ship on a long cable, the researchers had to wait for the calving event before they could explore the previously unreachable seafloor. In the future, new technologies like autonomous underwater robots will be used to investigate such habitats.