World’s longest time series

Far-sighted scientists at the University of Bergen and the Institute of Marine Research ensured that the University currently possesses some of the longest and most important deep-sea time series in the world.

The weather ship “Polarfront,” which is stationed at Station M, far out in the Norwegian Sea , has been making daily meteorological and oceanographic observations since as far back as 1948. After the Second World War, weather ships were stationed out in the Atlantic Ocean to help airlines work out how much fuel they would need to fly between Europe and the USA . In the course of time, aviation technology improved so much that the weather stations were no longer needed. However, Norway ’s Station M was left in position, and with its measurement series covering 65 years, the station is the most valuable resource we now have for deep-sea climate research. At the same time, the University of Bergen and the Institute of Marine Research have set up measurement stations to register how much of the life-giving warm Gulf Stream enters the Norwegian Sea and is transported onwards north to the Barents Sea and the Arctic Ocean . The University’s Bjerknes Centre is coordinating a major European project (MOEN), which measures the water that enters all the branches of the Norwegian Sea between Scotland and Greenland , in addition to the cold, heavy water that flows south along the bottom of the sea towards the Equator.

Shedding new light on climate change

“Our long time series from the Norwegian Sea show the volume of deep water that flows over the underwater ridge near the Faeroes has fallen by 25 percent during the past 50 years. We have related these data to recent deep-water measurements from channels in this region and found that while the ocean current from the Norwegian Sea to the Equator has become weaker and less saline, the current in the other direction is both saltier and warmer. This process helps to maintain what is known as the thermohaline circulation,” says Svein Østerhus, who is leading the MOEN project at the Bjerknes Centre. This means that the circulation of water in the Norwegian Sea will not cease completely, as has been predicted by some climate models. The coinage “thermohaline circulation” is used of the major ocean currents that carry warm surface water from the Equator to the poles, and cold deepwater back to the Equator. In the Norwegian Sea and the Arctic Ocean the water cools down again, and when it turns to ice the water that does not freeze becomes more salt. Both of these processes also make the water heavier, which means that it sinks and flows southwards through the North Atlantic and on to the Equator. This large-scale ocean circulation plays a major role in maintaining the warm ocean current that flows north along the coast of Norway.

Better basis for climate prognoses

Together with colleagues from the Faeroes, Germany and Scotland, Østerhus has pointed out in a recent article in “Science” the importance of temperature and salinity variations when we are studying changes in ocean circulation systems. In autumn 2004, the research vessels “G.O. Sars” took scientists to an area off the Faeroes to collect samples of sediment. Palaeo-oceanographic data can answer questions about the strength of the ocean currents during the past thousand years, and conjunction with the deep-sea data this could give us a better basis for making prognoses about the climate.

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