It was one of the largest and most complex expeditions to the Arctic that has ever existed: the German research icebreaker was on board from September 2019 North Star traveling in the Arctic for a good year. Frozen in the ice, the ship drifted through the Arctic during the winter months, passing close to the North Pole. Since returning in October 2020, researchers have been busy evaluating the data collected during the Mosaic expedition. They have now published three first review articles.
The work published on Monday in the journal elementa were published deal with the processes in the atmosphereWith snow and ice as well as with the processes in the ocean. Together they provide a first picture of the change mechanisms in the Arctic, which is warming up around twice as fast as the rest of the world – which not only has dramatic consequences for the ecosystems there, but also has a global impact on weather and climate.
A surprise for the changing research teams on board the North Star was the amazing speed at which the pack ice was drifting through the sea. “This not only challenged the teams on site in their daily work on the floe, but above all led to changed sea ice properties and sea ice thickness distributions,” says Marcel Nicolaus, sea ice physicist at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research ( AWI), and co-leads the ice team in the Mosaic project.
The polar vortex was particularly strong from January to March 2020
In the analysis, the researchers attribute this to the special conditions of winter 2019/2020: It was very cold on the surface, which was associated with strong winds, so that the ice was pushed faster than usual. This is probably also related to the unusually strong polar vortex from January to March 2020. If this high-altitude wind is particularly pronounced around the Arctic, little warm air can penetrate. In the winter of the Mosaic expedition, this also led to a record ozone hole forming in the stratosphere.
The winds also affected the distribution of snow and ice. The spatial fluctuations were larger than expected. In some places the snow settled, in others it was swept away; here the researchers found cracks in the ice, there high press ice ridges piled up. Short-term events such as storms, periods of warm weather or precipitation had a significant impact on snow and sea ice for months. With these findings, the researchers now hope to be able to improve climate models in the future.
There was also more movement below the ice layer than expected. “We observe an increasing connection between the upper ocean and the deeper warm water layers in the central Arctic Ocean, all year round,” says Céline Heuzé, physical oceanographer at the University of Gothenburg and co-leader of the Mosaic Ocean team.
However, the three articles are only the beginning, the evaluation of the collected data will keep the scientists busy for years to come. Through the unique combination of comprehensive physical and biological observations, they hope to finally gain a better understanding of what rapid warming is doing to the Arctic – and what that could mean for the rest of the world.