Average winter temperatures in northern Europe are at least 10 degrees Fahrenheit warmer than similar latitudes on the northeastern coast of the United States and the eastern coast of Canada. The same phenomenon happens over the Pacific Ocean, with winters on the northeastern coast of Asia being regularly colder than in the same latitude in the Pacific Northwest.
And the culprit for these cooler winters, is warm waters.
“These warm ocean waters off the eastern coast actually make it cold in winter—it’s counterintuitive,” says Tapio Schneider, the Frank J. Gilloon Professor of Environmental Science and Engineering at California Institute of Technology (Caltech).
These seemingly contradictory findings are published in the most recent edition of the journal Nature, and are based on computer simulations of the atmosphere which showed the anomalous findings.
The researchers found that warm water off an eastern coast – such as the east coasts of Asia and America – will lead to the air above it heating which lead to the formation of atmospheric waves which draw the cold air from the northern polar region.
As a result, cold air forms just to the west of the warm water.
Thus, warm waters off the eastern shores of the United States and Canada will form cold plumes above the east coast leading to much cooler winters than across the pond on the same latitude.
The work done by Schneider and Yohai Kaspi, a postdoctoral fellow at Caltech and co-author of the paper adds to a continual reshaping of our understanding of how the oceans affect land-based temperatures. It was only in 2002 that we discovered the Gulf Stream is simply not capable of delivering enough heat to affect the cross-oceanic temperature differences seen between the US and Europe, instead contributing only about 10 percent of the warming that takes place.
This new work shows that, instead of the Gulf Stream warming Europe, as had previously been thought to account for the temperature differences, the warm Gulf Stream waters which move up from the Gulf of Mexico are actually cooling the east coast of North America.
“It’s not that the warm Gulf Stream waters substantially heat up Europe,” Kaspi says. “But the existence of the Gulf Stream near the U.S. coast is causing the cooling of the northeastern United States.”
For the scientific explanation behind this new discovery, head on over to Caltech’s press release and scroll to halfway through the article for explanations as to just what a Rossby wave is and why it is behind this new discovery.