Greenhouse gases inhibit ocean pump

Warming of surface water hinders circulation in the North Atlantic

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If greenhouse gas concentrations increase by one percent per annum, the climate-critical "circulating pump" in the North Atlantic will be considerably weakened. New climate models show that especially the warming of the surface water could be responsible for this.


In the waters of the North Atlantic sits a huge "circulation pump", a sea circulation in which warm surface water sinks and cold deep water is transported towards the south. Without this "pump", the heat transport in the oceans would be disturbed and the Gulf Stream - climate-determining for much of Europe - would also fail.

Among other things, climate researchers have been studying for years what effects global warming could have on this circulation pump. Their fear: the glacial meltwater that flows in more strongly could lower the salinity of the seawater, disturbing the delicate balance of ocean circulation or even bringing the "pump" to a standstill. And also the effects of a warming of the surface water are only partially known.

North Atlantic response to warming studied

A team of Canadian researchers, led by Andrew J. Weaver of the University of Victoria, has once again examined the response of the North Atlantic to warming with the help of several model calculations and simulations. It turned out that, even if the starting conditions were different, the North Atlantic circulation pump always weakened when the concentration of greenhouse gases in the atmosphere increased by one percent per year. This increase triggered a warming, which in turn increased the ice melt and thus also the fresh water inflow in the North Atlantic. display

Interestingly enough, the strongest effect did not occur when the initial pumping power in the North Atlantic was already weak anyway, but when it was particularly pronounced. The weakening caused by the warming was then particularly blatant. The strongest effect was also the model showed, not from the increased inflow of meltwater, but from the warming of the surface water.

(American Geophysical Union, 27.02.2007 - NPO)