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Polarstern: Researching the effects of climate change

Polarstern: Researching the effects of climate change

As of: October 1, 2023 at 4:27 p.m

A scientific team led by the Alfred Wegener Institute has been conducting research in the Arctic for about two months. And now the Polarstern has returned, carrying exciting data in its luggage.

By Caroline Henkenprince, Radio Bremen

Six-metre-high waves hit the side of the ship, and white spray violently splashed across the deck: Polarstern was on her way back to Bremerhaven when the icebreaker got caught in a violent storm in the North Atlantic. Photos and videos show this impressively.

Only a few days later, the Polarstern lies in Bremerhaven harbor in the rain – as if nothing had ever happened. Captain Stefan Schwarz stands on the bridge and says: “This ship is a stroke of luck.” The “Old Lady,” as the 42-year-old research vessel is called, is not only a good icebreaker, but thanks to the shape of its hull, it lies more quietly in the water than other ships.

And besides, the sailor says, he’s already been through some storms.

Arctic sea ice is melting

The German research ship has been traveling in the Arctic for two months. There were 54 researchers and 43 crew members on board. The Alfred Wegener Institute (AWI) for Polar and Marine Research based in Bremerhaven led the expedition. Dozens of other institutions from Germany, Japan and the USA also participated.

The science team investigated how climate change will affect the Arctic at nine stations. The Arctic is key to understanding global warming. According to a study, the region around the Arctic has warmed almost four times faster than the world as a whole over the past 40 years.

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Consequences: Arctic sea ice has melted dramatically over the past 30 years, and the life and animal world of the Arctic Ocean is also changing. Therefore, the AWI-led team included not only physicists, meteorologists and oceanographers, but also biologists who conducted research under the ice.

Amazing measurement results

The results returned by the team were surprising: Contrary to expectations, there was no new ice melt record this summer, AWI director and crew leader Antje Boetius reported in tagesschau24-interview. This was expected when the expedition began at the beginning of August, also due to the global summer heat.

Instead, the thickness of the ice at the beginning of September was 1.2 metres, which was about 20 to 30 centimeters thicker than expected, said Marcel Nicolaus, a researcher at the AWI. In addition – unlike usual in an Arctic summer – there was a lot of snow on the ice. “That was really extraordinary,” the sea ice physicist said. These observations initially puzzled scientists.

Weather anomalies alter ice drift

With the help of a colleague who was at home in Bremerhaven and entered the polarstern data into a model, it became clear: the cause was a weather anomaly. A series of low-pressure areas changed the movement of the ice, called transpolar drift. Unlike the past 30 years, ice has not drifted from the Siberian shelves into the Arctic region studied; Instead the ice came from the Canadian Basin.

For AWI director Boethius, such a weather phenomenon is clearly no reason to clarify matters. Because with a little more bad luck, Arctic sea ice could melt much faster than expected. Forecasts will become increasingly difficult.

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There is barely any algae under the ice

In many places, the science team has discovered less life under the ice than it had on the same expedition eleven years earlier. The researchers were unable to find any algae or even algae forests under the ice. One of these algae is the filamentous Melosira arctica. It is thinner than a human hair and grows like a carpet on the underside of Arctic sea ice. When sea ice melts in summer, the algae stick together and sink to the sea floor.

During the 2012 expedition, Boeotius found several of these clumps of algae. Not this year. This is why there are no longer any animals at the bottom of the sea that feed on algae, only traces of it. Boethius says this shows how surface is related to depth. That the Arctic must be understood as a system.

The absence of algae is also caused by shifting ice. Boetius said it comes from an area where algae does not exist.

Now the real work begins

When they returned, the researchers’ work had already begun: they brought with them 100 ice samples and 11,800 liters of water samples. Why so much water? The water was taken from about 30 places, always from different depths of the sea, explains Nicholas, a sea ice physicist. Water filtration is often necessary to analyze salt, chlorophyll or carbon content. That’s why you need a lot.

Captain Schwarze can also see how much the Arctic has already changed. He, who had been there at least 30 times, noticed distinct differences when he drove through the snow in a PolarStern. “It’s gotten quieter,” he says. It cracked when the solid ice beneath the ship broke.

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Things are different now due to climate change and melting sea ice. Today, Schwartz says, the drive through the ice is silent.