Fifty Degrees Below Read Online Free Page A

about the Gulf Stream.”
    “Good.”
    Kenzo and a couple of his colleagues in climate duly appeared. They exchanged hellos, got out laptops, and Kenzo started working the PowerPoint on Diane’s wall screen.
    All the data, Kenzo explained, indicated stalls in what he called the “thermohaline circulation.” At the north ends of the Gulf Stream, where the water on the surface normally cooled and sank to the floor of the Atlantic before heading back south, a particularly fresh layer on the surface had stalled the downwelling. With nowhere to go, the water in the current farther south had slowed to a halt.
    What was more, Kenzo said, just such a stall in the thermohaline circulation had been identified as the primary cause of the abrupt climate change that paleoclimatologists had named the Younger Dryas, a bitter little ice age that had begun about eleven thousand years before the present, and lasted for a few thousand years. The hypothesis was that the Gulf Stream’s shutdown, after floods of fresh water had come off the melting ice cap over North America, had meant immediately colder temperatures in Europe and the eastern half of North America. This accounted for the almost unbelievably quick beginning of the Younger Dryas, which analysis of the Greenland ice cores revealed had happened in only three years. Three years, for a major global shift from the worldwide pattern that climatologists called warm-wet, to the worldwide pattern called cool-dry-windy. It was such a radical notion that it had forced climatologists to acknowledge that there must be nonlinear tipping points in the global climate, leading to general acceptance of what was really a new concept in climatology: abrupt climate change.
    “What caused the stall again?” Diane said.
    Kenzo clicked to the next slide, an image of the Earth portraying the immense ice cap that had covered much of the northern hemisphere throughout the last ice age. The end of that one had arrived slowly, in the old-fashioned linear way, melting the top of the ice cap and creating giant lakes that rested on the remaining ice. These lakes had been held in place by ice dams that were themselves melting, and when the dams had at last given way, extraordinarily large floods of fresh water had rushed down into the ocean, emptying volumes as large as the Great Lakes in a matter of weeks. Signs left on the landscape indicated this had happened down the watersheds of the St. Lawrence, the Hudson, and the Mississippi, and out west, a lake covering most of Montana had drained down the course of the Columbia River several times, leaving an area in Washington called the scablands which gave eloquent testimony to the power of these floods to tear into the bedrock. Presumably the same thing had happened on the East Coast, but the signs had mostly been submerged by rising sea levels or the great eastern forest, so that they were only now being discerned.
    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