Geek's garden

13.03.2006
Computer model confirms ancient flood

Scientists at NASA and Columbia University in New York have used computer modeling to successfully reproduce an abrupt climate change that took place 8,200 years ago. At that time -- the beginning of the current warm period -- climate changes were caused by a massive flood of fresh water into the North Atlantic.

This work is the first to consistently re-create the event by computer modeling, and the first time that the model results have been confirmed by comparison to the climate record, which includes ice-core and tree-ring data.

"We only have one example of how the climate reacts to changes -- the past," said Gavin A. Schmidt, a researcher at the NASA Goddard Institute for Space Studies (GISS) and co-author on the study. "If we're going to accurately simulate the Earth's future, we need to be able to replicate past events. This was a real test of the model's skill."

The study was led by Allegra LeGrande, a graduate student in the department of earth and environmental sciences at Columbia. The results appeared in the journal Proceedings of the National Academy of Sciences in January.

The group used an atmosphere-ocean coupled climate computer model known as GISS Model E-R to simulate the climate impact of a massive freshwater flood into the North Atlantic that happened after the end of the last Ice Age. Retreating glaciers opened a route for two ancient meltwater lakes, known as Agassiz and Ojibway, to suddenly drain from the middle of the North American continent.