Research linked European climate variability to the temperature swings of its neighboring ocean in the spring, summer, and fall.

Surprisingly, however, no imprint of the ocean’s variability could be found in Western Europe’s wintertime temperature record. This absence was especially puzzling in light of the fact that Europe’s mild winters are a direct consequence of its enviable location downwind of the North Atlantic.

Now, a study by researchers at McGill University and the University of Rhode Island suggests the answer to this puzzle lies in the winds themselves. The fluctuations in ocean temperature are accompanied by shifts in the winds. These wind shifts mean that air arrives in Western Europe via very different pathways in decades when the surface of the North Atlantic is warm, compared to decades when it is cool.

72 winters

The researchers studied the winds and their interaction with the ocean in a recently developed reconstruction of 20th-century climate. Their main approach was to launch virtual particles into the winds, and trace their journey for ten key days leading up to their arrival in Western Europe. They repeated this procedure using the wind field for each winter of the last 72 years, a period for which the winds of the North Atlantic have already been carefully documented and validated.

The new research reveals that in decades in which North Atlantic sea surface temperatures are elevated, winds deliver air to Europe disproportionately from the north.

In contrast, in decades of coolest sea surface temperature, swifter winds extract more heat from the western and central Atlantic before arriving in Europe. The researchers suggest the distinct atmospheric pathways hide the ocean oscillation from Europe in winter.

Whether the atmosphere is the tail to the ocean’s dog or vice versa remains up for debate.

“There is an ongoing argument about whether the ocean circulation sets the slow temperature fluctuations at its surface, or the atmosphere is the more important agent,” says University of Rhode Island professor Jaime Palter, one of the authors.

If, as many climate models suggest, the ocean is a main driver, then this research has implications for the future of European climate. A system of ocean currents, popularly referred to as the “Great Ocean Conveyor,” brings warm waters to the North Atlantic.

This current system is predicted to slow down in response to global warming, causing the North Atlantic to cool.

Source: futurity.org; sciencedaily.com;yale.edu . Image source:Unsplash.com