Using a new theory, Erwin Lambert shows that more freshwater in the Arctic may strengthen the Gulfstream’s extension into the polar regions — the opposite of what has generally been anticipated with future climate change.
(From ScienceDaily)– A new study from researchers at the Bjerknes Centre for Climate Research gives less reason to fear a weakening of the Gulfstream due to climate change. One of the suggested ‘tipping points’ in the climate system is a substantial slow-down or even collapse of the Gulfstream due to increased freshwater input in the northern seas. In a warmer climate, the hydrological cycle of precipitation and evaporation will strengthen including more rainfall, river runoff and ice melt in the north. One can in its most extreme imagine this literally to close the large-scale ocean circulation between the Arctic and the lower latitudes.
In the article ‘How northern freshwater input can stabilise thermohaline circulation’, Erwin Lambert, PhD-student at UiB and the Bjerknes Centre and the University of Bergen, studies how ocean circulation is affected by increased freshwater input. Lambert and colleagues show how increased freshwater input in the north in some cases can even strengthen the Gulfstream extension into the Arctic — just like a river in a typical Norwegian fjord is a driver for the fjord’s exchange with the surrounding ocean.
In 1961, the American oceanographer Henry Stommel reduced the ocean to a few equations. With Stommel’s model, the North Atlantic can be split into a warm part in the south and the cold Nordic Seas in the north — a thought experiment of two boxes, without coastlines, islands or underwater ridges. In the North Atlantic, water flows northward at the surface, before sinking to the bottom in the Nordic Seas and flowing back southward in the deep ocean. The surface current flowing north is what we think of as the Gulf Stream. Stommel’s description of how water circulates between warm and cold regions like this, was entirely theoretical, and it was the Finnish oceanographer Clas Rooth who applied it to the Atlantic in 1982.
Read the full article here: https://www.sciencedaily.com/releases/2016/11/161124081751.htm