Gulf Stream sea surface temperature

The Gulf Stream carries vast amounts of heat toward Europe. NOAA

Early in his career, Harry L. Bryden was fascinated by an unanswered question: How much heat does the Gulf Stream carry north?

Using data on the Gulf Stream's velocity off Florida, they came up with a mind-blower: The Gulf Stream transported 1.2 Petawatts of heat energy every second. That's the equivalent heat energy produced by more than a million 1,000-megawatt nuclear power plants going full tilt. 

“The ocean is like a radiator heating the atmosphere above,” he said.

Later, Bryden helped lead an international effort to monitor the AMOC, short for Atlantic meridional overturning circulation. The AMOC is the conveyor belt of water that flows in the Gulf Stream and then sinks in the Arctic as it cools, joining currents flowing south along the seabed.

The effort involved stringing stations across the Atlantic, from Florida to the coast off West Africa. In 2004, scientists had their first look at the stations' data. They discovered the AMOC's variability was four times larger than earlier estimates. In other words, its flow wasn't static.

But the big surprise came in 2009, when instruments recorded a 30 percent slowdown in the AMOC.

“Nobody had ever thought such an event could happen,” Bryden said.

The current regained much of its strength in 2010 but remains in a weakened state.

Bryden said the Gulf Stream isn’t in danger of shutting off, and that much of the changes are in other components of the AMOC.

But the race to learn about these currents has only grown more urgent as scientists continue to uncover their mechanics and power.

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For a deeper dive into the Gulf Stream and the amazing and disturbing things happening to it, visit our new special report: Into the Gulf Stream

Reach Tony Bartelme at 843-937-5554. Follow him on Twitter @tbartelme.

Tony Bartelme is senior projects reporter for The Post and Courier. He has earned national honors from the Nieman, Scripps, Loeb and National Press foundations and is a three-time finalist for the Pulitzer Prize. Reach him at 843-937-5554 and @tbartelme