The same was probably true just before the Yonger Dryas set in. But as the vast Ice Age glaciers retreated, their melt water flowed into the northern reaches of the Atlantic Ocean. The injection of fresh water made the sea easier to freeze, and a new skin of ice began advancing south. The warm conveyor belt of Gulf Stream waters soon ebbed to a trickle. And as the sea ice advanced, the winds shifted into a west-east pattern. Within a year the breezes that warmed Europe had vanished. "The Younger Dryas continues to surprise us in providing a message as to how quickly climate change can occur," said Daniel Sigman of Princeton University in N.J. Sigman is a co-author on the study, which appears today in the journal Nature Geoscience. "The hypothesis on this paper is I think a very nice one," Richard Alley of Pennsylvania State University said. Winds tend to blow parallel to temperature gradients, and the gradient between sea ice and open water can be very sharp, up to 40 degrees C. The sea ice border probably extended in a rough west to east direction, and the winds would've followed it, bringing cold air to much of Europe. "You can think of it as a front pushing down across Germany," Alley said. "Winds go where something's pushing them hard. A steep temperature gradient along the edge of sea ice would push hard in an east-west direction." Related Links: |
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