Water Cycle Magnifies Abrupt Climate Change, Study Suggests

Changes in the water cycle were major players in the large scale environmental change that occurred in western Europe during the Younger Dryas period some 12,680 years ago, a new study found.

The Younger Dryas period, also known as the Big Freeze, lasted from about 12,800 and 11,500 years ago, and marked the last significant cold spell at the end of the the last glaciation. Published in the journal Nature Geoscience, the discovery is evidence that the role of the hydrological cycle during periods of abrupt temperature change is key when it comes to the impact of climate change on continents.

The researchers analyzed organic remains from Meerfelder maar lake sediments in western Germany, which they used to piece together changes in precipitation patterns. In doing so, they discovered that the influx of dry polar air into the region triggered the collapse of the area's ecosystems, leading to environmental changes throughout.

"In our new study we can show for the first time that this change in the pathway of westerly wind systems brought dry polar air into western Europe and this was the ultimate cause for the widespread disappearance of forests in the area," said Dirk Sachse, the head of the workgroup at the Institute of Earth and Environmental Sciences of the Potsdam University.

The results support the idea that this shift in atmospheric circulation patterns occurred 170 years after cooling began - a delay the researchers blame on the southward expansion of sea ice in the North Atlantic that took place once the cooling started. The result was a southward shift of the polar front transporting dry polar air into western Europe.

"Our results also show that abrupt climate and environmental change may not be coeval on large regional scales, but can take place with substantial regional and temporal delays," said Achim Brauer from the GFZ German Research Center for the Geosciences.

In the end, the researchers argue that the study proves not only that temperature changes can result in different regional impacts, but that the water cycle can magnify changes to have a potentially drastic effect on continental ecosystems.