Polarstern sets sail for the Antarctic

Oceanographers will investigate the melting processes at work in shelf ice, which can lead to the calving of huge icebergs

On Wednesday 20 December 2017, the research vessel Polarstern set sail south from Bremerhaven. After a stop in Cape Town, it will deliver supplies to the Neumayer Station III, and the researchers will subsequently gather vital data at the Filchner-Rønne Ice Shelf in the southern part of the Weddell Sea, which is permanently covered by sea ice, in order to examine the melt rates of the Antarctic glaciers. From March 2018, biologists will investigate marine life around the Antarctic Peninsula. Oceanographic studies will be carried out on the return trip to Bremerhaven, where the icebreaker is expected to arrive on 11 June 2018.

It’s the second largest of its kind in the world: the Filchner-Rønne Ice Shelf in the southern Weddell Sea has an area of roughly 450,000 square kilometres and holds a greater volume of ice than any of the other giant glacier ice tongues floating in the sea. In July 2017 an enormous iceberg calved from the Larsen C Ice Shelf. Climate researchers are particularly interested in whether more glacial ice is being transported into the sea – since this process is relevant for rising sea levels. In addition, so-called deep water forms near the ice shelf, which acts like a pump for global ocean circulation, affecting the climate system everywhere on Earth.

Infographic: How the ocean heat attacks an ice-shelf (Photo: Martin Künsting)

Researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), the British Antarctic Survey and the University of Bergen launched the joint FISP (Filchner Ice Shelf Project) in 2013. The aim is to describe the current state of the complex atmosphere-ice-ocean system: “We are investigating the change in ocean circulation and the influx of warm water beneath the ice shelf using moorings equipped with measuring devices on the sea bed,” explains Dr Michael Schröder, head of the Polarstern expedition to the Antarctic.

“The data we collect is vital for validating the high-resolution coupled atmosphere-ice-ocean models developed at the AWI. They allow us to make more reliable predictions about how the entire system will respond to climate change,” adds the AWI oceanographer. For example, in May 2017 AWI researchers working with Dr Hartmut Hellmer published a study on the stability of the future thermal influx beneath the ice shelf. The first analysis of the temperature and flow measurements from the FIS Project confirms that there are periodic influxes of warm water beneath the ice shelf. On board the Polarstern, the oceanographic measurements will be supplemented by data from sensors that collect information on the temperatures, salinity and flows in the entire water column beneath the hundreds of metres thick ice shelf.

Alongside oceanographers, researchers from disciplines like meteorology, sea-ice physics, bathymetry, geology and marine biology will also take part in this Antarctic expedition, known as PS111. They all share an interest in obtaining data from a region that, due to its permanent ice cover, can only be investigated with icebreakers like the Polarstern. “One exciting challenge will be deploying underwater vehicles, which dive below the ice,” comments chief scientific officer Michael Schröder, who will coordinate the various measuring programmes. If the weather permits, he and his team intend to stop off en route to the Antarctic in order to investigate a special phenomenon. In the last southern winter, the so-called Weddell Polynya formed for the first time since the 1970s: for more than three months there was an 80,000-square-kilometre ice-free zone in the middle of the winter sea ice. According to Schröder, “The exact physical conditions for this temporary disappearance of sea ice are not yet completely understood, which is why scientists from around the globe are interested in measurements from this region.”

The subsequent expedition, which will start in Punta Arenas, Chile in mid-March 2018, will take us to the ocean region off the Antarctic Peninsula, where biologists will study salps and krill. A team of oceanographers will use the return trip across the Atlantic to Bremerhaven to test a new towed measuring system. On the voyage from Bremerhaven to the Antarctic via Cape Town, ten scientists will deploy acoustic systems, e.g. to measure the ocean floor. The Polarstern set sail with the midday high tide at about 1.30 pm on 20 December.