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Global warming: Sea ice decline causing ozone depletion

Arctic ozone vanished at an unprecedented rate in the winter of 2010-2011.

New research suggests that sea ice loss may also be resulting in more mercury deposition in the Arctic

By Summit Voice

SUMMIT COUNTY — Loss of sea ice in polar regions isn’t just affecting the surface of the Earth, but is also having an impact on the atmosphere.

An international NASA-led team, coordinated by the National Ice Center,  is reporting that changes in sea ice are driving chemical reactions that result in ozone depletion and the toxic element mercury falling out of the Arctic atmosphere onto the ocean and icy surface.

The findings may help explain why other studies documented an unprecedented loss of ozone in the Arctic last winter.

Mercury could adversely affect the health of people and wildlife in the Arctic, and the ozone depletion finding gives scientists new insight on Arctic ozone changes in the troposphere.

A large amount of the thicker Arctic sea ice cover has been disappearing due to increased melting during summer months and year-round seawater flowing out of the region through the Fram Strait (a passage from the Arctic Ocean to the Greenland and Norwegian seas). This thicker ice is then replaced with new, thinner ice in the winter months, so that the ratio of old, perennial ice to new, seasonal ice has shifted.

“The seasonal or first-year ice is saltier and thinner than the old ice and is also characterized by fractures and leads [linear cracks in the ice that form when ice floes diverge or shear as they move parallel to each other] that provide the lower atmosphere with increased exposure to sea salts including bromine,”said NOAA’s Pablo Clemente-Colón.

Scientists believe that as some of this bromine escapes into a cold atmosphere in the presence of sunlight, it sets off reactions that remove ozone and mercury from the air.

“We also discovered that mountain ranges in Alaska and the western Northwest Territories in Canada limit the horizontal distribution of Arctic bromine in the atmosphere. This work could dramatically impact our understanding of ozone depletion in the polar regions,” said Clemente-Colón. “It establishes that some of the Arctic ozone depletion observed from satellites during early spring is actually happening in the troposphere, the lower part of the atmosphere, instead of the stratosphere.”

This difference is significant: Ozone in the lower atmosphere can have harmful health effects, but in the upper atmosphere (stratosphere) it forms a layer that shields the earth from harmful ultraviolet radiation.

The researchers’ findings will be published in the Journal of Geophysical Research-Atmospheres. The team has just completed a Spring 2012 study to better understand the impacts of reduced sea ice on atmospheric chemistry in the Arctic.

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