The Gulf Stream’s Weakening Arm

Again, exceptional infographics tell an important environmental story–it is worth opening if only for the quality of the interactive illustrations:

In the Atlantic Ocean, Subtle Shifts Hint at Dramatic Dangers

The warming atmosphere is causing an arm of the powerful Gulf Stream to weaken, some scientists fear.

By MOISES VELASQUEZ-MANOFF
and JEREMY WHITE

IT’S ONE OF THE MIGHTIEST RIVERS you will never see, carrying some 30 times more water than all the world’s freshwater rivers combined. In the North Atlantic, one arm of the Gulf Stream breaks toward Iceland, transporting vast amounts of warmth far northward, by one estimate supplying Scandinavia with heat equivalent to 78,000 times its current energy use. Without this current — a heat pump on a planetary scale — scientists believe that great swaths of the world might look quite different.

Now, a spate of studies, including one published last week, suggests this northern portion of the Gulf Stream and the deep ocean currents it’s connected to may be slowing. Pushing the bounds of oceanography, scientists have slung necklace-like sensor arrays across the Atlantic to better understand the complex network of currents that the Gulf Stream belongs to, not only at the surface, but hundreds of feet deep.

“We’re all wishing it’s not true,” Peter de Menocal, a paleoceanographer and president and director of the Woods Hole Oceanographic Institution, said of the changing ocean currents. “Because if that happens, it’s just a monstrous change.”

The consequences could include faster sea level rise along parts of the Eastern United States and parts of Europe, stronger hurricanes barreling into the Southeastern United States, and perhaps most ominously, reduced rainfall across the Sahel, a semi-arid swath of land running the width of Africa that is already a geopolitical tinderbox.

The scientists’ concern stems from their understanding of thousands of years of the prehistoric climate record. In the past, a great weakening or even shutdown of this arm of the Gulf Stream seems to have triggered rapid changes in temperatures and precipitation patterns around the North Atlantic and beyond.

The northern arm of the Gulf Stream is but one tentacle of a larger, ocean-spanning tangle of currents called the Atlantic Meridional Overturning Circulation, or AMOC. Scientists have strong evidence from ice and sediment cores that the AMOC has weakened and shut down before in the past 13,000 years. As a result, mean temperatures in parts of Europe may have rapidly dropped to about 15 degrees Celsius below today’s averages, ushering in arctic like conditions. Parts of northern Africa and northern South America became much drier. Rainfall may even have declined as far away as what is now China. And some of these changes may have occurred in a matter of decades, maybe less.

The AMOC is thus a poster child for the idea of climatic “tipping points” — of hard-to-predict thresholds in Earth’s climate system that, once crossed, have rapid, cascading effects far beyond the corner of the globe where they occur. “It’s a switch,” said Dr. de Menocal, and one that can be thrown quickly.

Which brings us to the cold blob. Almost everywhere around the world, average temperatures are rising — except southeast of Greenland where a large patch of the North Atlantic has become colder in recent years…

Read/experience the whole story here.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s