Frank, looking at the map on the screen, thought of how Rock Creek had looked that morning at dawn. Theirs had been a very tiny flood relative to the ones Kenzo was describing, and yet the watershed was devastated.

So, Kenzo continued, fresh water, dumped into the North Atlantic all at once, appeared to block the thermohaline cycle. And nowadays, for the last several years, the Arctic Ocean’s winter sea ice had been breaking up into great fleets of icebergs, which then sailed south on currents until they encountered the Gulf Stream’s warm water, where they melted. The melting zones for these icebergs, as a map on the next slide made clear, were just above the northern ends of the Gulf Stream, the so-called downwelling areas. Meanwhile the Greenland ice cap and glaciers were also melting much faster than had been normal, and running off both sides of that great island.

“How much fresh water in all that?” Diane asked.

Kenzo shrugged. “The Arctic is about ten million square kilometers. The sea ice lately is about five meters thick. Not all of that drifts into the Atlantic, of course. There was a paper that estimated that about twenty thousand extra cubic kilometers of fresh water had diluted the Arctic over the past thirty years, but it was plus or minus five thousand cubic kilometers.”

“Let’s get better parameters on that figure, if we can,” Diane said.

“Sure.”

They stared at the final slide. The implications tended to stall on the surface of the mind, Frank thought, like the water in the north Atlantic, refusing to gyre down. The whole world, ensconced in a global climate mode called warm and wet, and getting warmer and wetter because of global warming caused by anthropogenically released greenhouse gases, could switch to a global pattern that was cold, dry, and windy. And the last time it happened, it had taken three years. Hard to believe; but the Greenland ice core data were very clear, and the rest of the case equally persuasive—one might even say, in science’s distinctive vocabulary of levels of certainty, compelling.