Oceanic planetary waves, just an inch or two high at the surface but thousands of feet deep and hundreds of miles apart, sweep slowly but steadily across Earth's oceans: a surfer who caught one in Acapulco would take four years to wash up on a Chinese beach. The waves are speeding up, though, thanks to global warming, and as they do, they could affect weather patterns around the world.

©Paulo Cipollini, Southampton Oceanography Centre
Schematic of a typical oceanic planetary wave traveling westward with horizontal scale of about 500 kilometers and with vertical amplitude at the sea surface of about 10 centimeters. Such waves have a major effect on the large-scale ocean circulation and thus on weather and climate.

The waves are constantly generated by surface winds and pushed westward by the Earth's eastward rotation. They advance by between four and ten inches a second in the tropics, more slowly toward the poles. But that's about 10 percent faster than oceanic planetary waves traveled at the start of the Industrial Revolution 200 years ago, according to John C. Fyfe and Oleg A. Saenko, both at the Canadian Centre for Climate Modelling and Analysis in Victoria, British Columbia. What's causing the speedup? Global climate models point to the temperature increase in the upper ocean - a consequence of increased atmospheric carbon dioxide. By 2100, the investigators add, if carbon dioxide levels rise as predicted, the waves will travel 35 percent faster than they did in preindustrial times.

Oceanic planetary waves affect ocean currents, which strongly influence continental weather and climate. As the waves speed up, Fyfe and Saenko forecast big changes that may include more frequent El Niño events and heat waves across western North America and Europe. (Geophysical Research Letters)

Link: John Fyfe