During a trans-Atlantic crossing in 1751, a slave trader named Capt. Henry Ellis began an ambitious experiment.
With help from an inventive pastor, he’d rigged a special bucket with flaps. The flaps opened when lowered and snapped shut when the motion stopped. This allowed Ellis to capture water samples at various depths.
While crossing, he took one sample after another and measured them with a thermometer. The lower he dipped that bucket, the colder the water — until he reached a depth of about 3,900 feet. Below that, the water temperature hovered at about 53 degrees. This was the case all the way down to 5,300 feet when he finally quit.
He couldn't figure out why the water temperature had leveled off. Shouldn’t it have become progressively colder? He was pleased anyway because he found a way to chill his wines.
Fifty years later, Benjamin Thompson, also known as Count Rumford, came across Ellis' letters.
Thompson, like his contemporary, Benjamin Franklin, was an inventor. Among Thompson's creations was a shallow fireplace that radiated heat more efficiently.
As the count read Ellis’ letters, he had another epiphany about heat. That deep layer of cold and salty water? It must have come from the Arctic.
Without the aid of satellites or computers, Thompson rightly figured out that the world had surface currents, such as the Gulf Stream, and other deeper and colder ones flowing in the opposite directions along the ocean floor.
And these currents were connected. The Gulf Stream's warm and salty flow sinks like a slow-motion waterfall as it moves between Greenland and Norway. Then it joins currents moving south along the ocean floor, including one that Capt. Henry Ellis dipped his bucket into.
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.