Gulf Stream defies climate change

Long-term study provides new insights

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The major ocean currents in the North Atlantic are subject to strong natural fluctuations, but so far there are no indications that the Gulf Stream is already weakening as a result of climate change. This is the result of a new long-term study carried out by scientists at the Leibniz Institute for Marine Research (IFM-GEOMAR) and the University of Kiel.

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Since 1996, the researchers have been studying the ocean currents in the North Atlantic. As a key region, this area of ​​the world ocean not only determines the climate in Northern Europe, but also has global long-range effects. As part of an international symposium, the scientists are now presenting the results of their work from 19 to 21 March 2007 in Kiel.

Strong natural fluctuations

"Almost all climate models show that the Gulf Stream will weaken in the future and some of our foreign colleagues thought they could detect the first signs of this in measurement data, " said Professor Claus Böning, oceanographer at IFM-GEOMAR and Spokesperson for the Collaborative Research Center (SFB) 460 " Dynamics of thermohaline circulation fluctuations ".

"However, this could not be confirmed in our long-term observations, " continued Böning. The northern North Atlantic is a critical region for the global climate. The sinking of water masses into great depths drives a global ocean circulation, which contributes over the extended arm of the Gulf Stream to a pleasantly mild climate in Northern Europe. display

This process is also a very sensitive set screw in the climate system and has been responsible for rapid and drastic global climate changes in the past. At the Kiel Collaborative Research Center, marine scientists collected a variety of data, which, together with high-resolution model simulations, led to a much better understanding of the complex processes in this region.

Climate change in northern Europe more moderate?

"Even if the predictions of the climate models are confirmed, here in Europe we will not sooner or later slip into an ice age, " emphasizes Professor Jürgen Willebrand, one of the authors of the recently published IPCC climate report, Böning's statement. "At best, the expected global warming in Northern Europe will be somewhat more moderate, " Willebrand continued.

In the funded by the German Research Foundation (DFG) with a total of 16 million euros program there were quite surprising results. Contrary to expectations, flow measurements at the output of the Labrador Sea showed large fluctuations over weeks and months, but so far no dramatic long-term trends suggesting a decrease in Gulf Stream circulation.

Computer simulations confirm observations

The observations coincide with the computer simulations of the very fine-meshed Kiel ocean model, which was propelled by atmospheric observation data. Nevertheless, measurement data such as model simulations still provide room for interpretation, and so the current results will certainly be discussed controversially at the closing event of the Kiel SFB. "We will definitely keep an eye on this key region for the global climate, " says Professor Martin Visbeck from IFM-GEOMAR. The importance is also recognized by the funding organizations such as the Federal Ministry of Education and Research (BMBF). Last year, the BMBF awarded a research program to a network of Kiel scientists, hamburger scientists and marine scientists in Bremen, with the aim of developing an "early warning system" for changes in the Gulf Stream system.

In this three-year project, the investigations can be continued. The results are also of great importance for the Kiel Cluster of Excellence "Ocean of the Future", which will intensively examine the opportunities and risks posed by the oceans over the next five years with new multidisciplinary research approaches.

(idw - Leibniz Institute for Marine Sciences, 19.03.2007 - DLO)