...Or maybe it's from hot air created by South American dictators...
"The current of the Gulf Stream has generally been
attributed to the waters of the Mississippi, especially as it was
observed that the water of the stream was several degrees warmer than
that of the ocean in its vicinity; and although this reason was
unsatisfactory to every geography-reading schoolboy, yet no more
rational theory was discovered till recently. It now appears that the
water of the Pacific flows by a subterranean channel to the Atlantic.
The high temperature of the water is now readily accounted for by a
knowledge that if this subterranean channel is three or four thousand
feet deep, it must pass through earth, the temperature of which is far
above the boiling point of water."
Scientific American, 1845