A few days ago, the captain and the head of the current Polarstern expedition jointly decided to abandon their efforts to reach the Larsen C Ice Shelf. Since dense sea ice and ice ridges blocked the planned route, the ship has now set course for alternative research sites further to the north.
“The dense sea ice had stacked up, forming ice ridges up to ten metres thick,” explains Polarstern’s captain, Thomas Wunderlich. “We spent seven days trying to break through the ice, but eventually realised that, given the situation, the only option was to seek more favourable ice conditions to the north.
The sea-ice extent in the Antarctic at the end of December – 4.94 million square kilometres – was the lowest recorded for the month since the beginning of continuous satellite monitoring (report at the Sea-ice Portal). However, expedition PS118 to the western Weddell Sea, encountered particularly dense and compacted regional sea ice north of iceberg A68.
“The alternative target regions, Larsen A and Larsen B Ice Shelves, were also out of the question. Even if we had reached them, we could have been trapped just as in Larsen C,” says Dr Boris Dorschel from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), and head of the expedition. Instead, he determined – after discussions with all of the research teams on board – that the fieldwork should now focus on a region in the northwest Weddell Sea. Following a line of sampling stations, the scientists will investigate how environmental conditions, such as sea-ice cover and primary productivity affect the ecosystem. The scientific results will, among other things, contribute to our understanding of how the Antarctic is responding to climate change. “We are now deploying our scientific equipment to investigate everything from the sea ice floating at the surface down to the bacteria in the mud on the seafloor and most things in between. We want to produce a comprehensive snapshot of the ecosystem, environment and animals that live in this frozen ocean.” says Dorschel.
In addition, the expedition team will take advantage of any gaps that appear in the sea ice that would allow them to investigate other areas further east. There, beyond the continental shelf, the seafloor rapidly plummets from 400 metres to more than 3000 metres. “If a window of opportunity presents itself, we will set course for those uncharted regions,” Dorschel explains. In addition to seafloor mapping work, the oceanographers hope to analyse the local water masses and currents to understand their role in global ocean circulation.
Even if the Larsen C and A68 remain out of reach for the moment, the expedition PS118 will provide crucial answers to many important research questions. As the head of the expedition aptly reviews: “Despite the difficult ice conditions, spirits are high on board, and we have plenty exciting science to do.”
