Sea ice is melting rapidly

Recording the climate and ecosystem of the Arctic Ocean

Mist in the Arctic Ocean. Florian Breier / AWI
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Large areas of the Arctic sea ice are only one meter thick this year and thus about 50 percent thinner than in 2001. This is the first result of an expedition to the Arctic Ocean conducted by the Alfred Wegener Institute for Polar and Marine Research.

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"The ice cover of the Arctic Ocean is dwindling, the ocean and the atmosphere are steadily warmer, the ocean currents are changing, " says Chief Scientist Ursula Schauer from the Alfred Wegener Institute, describing the current observations. It is traveling in the Arctic with 50 scientists from Germany, Russia, Finland, the Netherlands, Spain, USA, Switzerland, Japan, France and China to study the state of ocean and sea ice.

During the two-and-a-half-month journey they discovered, among other things, that not only the ocean currents but also the communities in the Arctic are changing. Exposed autonomous measuring buoys should provide valuable data from this currently strongly changing ocean even after the end of the expedition with the research vessel Polarstern.

Dramatic change

"In the midst of a dramatic change in the Arctic, the International Polar Year 2007/08 provides a unique opportunity to explore this ocean of change across disciplines and countries, " said Schauer. display

Oceanographers aboard the research vessel Polarstern investigate the composition and circulation of water masses, the physical nature of sea ice and the transport of biochemical and geochemical components in ice and seawater. The ecosystems in the sea ice, in the water and on the seabed are also the focus of observations. Scientists extract sediment cores from the seabed to reconstruct the climatic history of the surrounding continents.

Autonomous oceanographic survey buoys are used for the first time in the International Polar Year in all regions of the Arctic Ocean. They drift across the Arctic Ocean, measuring the current, temperature and salinity of the ocean. The buoys regularly transmit this data via satellite directly into the laboratories of the scientists.

Also new is the use of a titanium measuring system, which for the first time allows contamination-free sampling of trace substances for the first time due to its high level of effectiveness. These studies are part of several research projects that all contribute to the International Polar Year.

Changes in sea ice

The thickness of the Arctic sea ice has decreased since 1979 and is currently about one meter in the central Arctic basin. Oceanographers also found a particularly high proportion of meltwater in the sea and a large number of melting ponds. These data collected on board Polarstern and from helicopters allow scientists to better interpret current satellite images.

Sea ice biologists from the Institute of Polar Ecology of the University of Kiel examine the animals and plants that live in and under the ice. They use the opportunity to explore this doomed ecosystem. According to the latest model calculations, the Arctic could be ice-free in less than 50 years on further warming. This could lead to the extinction of many organisms adapted to this habitat.

Ocean currents under the magnifying glass

Ocean currents in the Arctic are an important part of global circulation. Warm water masses, which flow in from the Atlantic, are changed in the Arctic by cooling and ice formation and sink into greater depths. Long-term measurements by the Alfred Wegener Institute for Polar and Marine Research over the past decade have shown considerable fluctuations and the warming of the incoming water from the Atlantic. The current expedition investigates the spread of these warm anomalies along different arms of the Arctic Ocean. The huge rivers of Siberia and North America transport enormous amounts of fresh water into the Arctic. This sap water acts as an insulating layer and controls the heat exchange between ocean, ice and atmosphere.

The investigations extend from the shelf areas of the Barents Sea, the Kara Sea and the Laptev Sea over the Nansen and the Amundsen Basin to the Makarow Basin. Between Norway and Siberia and into the Canadian basin, scientists have so far carried out temperature, salinity and flow measurements at more than 100 stations. First results show that the temperature of the influx from the Atlantic is lower than in the previous year.

Also in the Arctic deep sea temperature and salinity change slowly. Here, the changes are small, but include thousands of meters of power and thus an enormous volume of water. In order to track the circulation even in winter, autonomous oceanographic measuring buoys are deployed on ice floes, which take measurements in the water while they drift with the ice. The measured data are transmitted via satellites.

Lower ice amphipods, small crustaceans at the bottom of the sea ice. Florian Breier / AWI

In addition to ocean currents and sea ice, the waterborne zooplankton, sediment deposits on the bottom of the sea and trace substances are also investigated. Zooplankton is the food source of many marine creatures and thus an important indicator of the state of the ecosystem. The deposits on the bottom of the Arctic Ocean record the changeful history of climatic changes on the surrounding continents like a diary. The scientists can use sedimentary cores to decipher the glaciations of northern Siberia. In addition, the expedition participants were able to measure trace substances from the Siberian rivers and shelf areas, which are transported by transpolar drift towards the Atlantic Ocean.

Project Transdrift

At the same time as the Polarsten Expedition, the Russian research vessel Ivan Petrov is traveling in the Laptev Sea to record the first effects of climatic changes on the Fronts and Polynja systems in the Laptev Sea and the consequences for global climate development. This will take place within the framework of the BMBF joint project System Laptev-See until September 20 with the Russian-German expedition Transdrift XII. For this purpose, marine observatories will be anchored for a period of two years and field studies will be carried out. The Expedition Transdrift XII is the first of seven expeditions in the next 30 months.

(idw - Alfred Wegener Institute for Polar and Marine Research, 14.09.2007 - DLO)