Global Warming

Global warming could shut down major ocean currents

Two new studies are adding to concerns about one of the most troubling scenarios for future climate change: the possibility that global warming could slow or shut down the Atlantic’s great ocean circulation systems, with dramatic implications for North America and Europe.

The research, by separate teams of scientists, bolsters predictions of disruptions to global ocean currents — such as the Gulf Stream — that transfer tropical warmth from the equator to northern latitudes, as well as a larger conveyor system that cycles colder water into the ocean’s depths.

Both systems help ensure relatively mild conditions in parts of Northern Europe that would otherwise be much colder.

The papers offer insight into how rapidly melting Arctic ice could slow or even temporarily halt the ocean’s normal circulation, with possible effects ranging from plunging temperatures in northern latitudes to centuries-long droughts in Southeast Asia.

One study, by three scientists from Germany’s Alfred Wegener Institute, uses computers to model how Greenland’s rapid thawing could affect the Atlantic meridional overturning circulation — the system that pushes cold, dense saltwater into the deep ocean and helps transport warm water northward, helping to moderate Europe’s climate.

A second paper, by a team of Texas scientists, sheds new light on how the Earth’s climate responded during a similar thaw from the planet’s geological past. About 12,000 years ago, rising temperatures at the end of the last ice age released huge volumes of cold freshwater, disrupting the ocean’s circulation systems and sending parts of the Northern Hemisphere back in to the freezer. Scientists refer to the era as the Younger Dryas period.