Impurities can move through ice cores, skewing climate research findings

Impurities trapped in ancient glacial or polar ice and used by researchers to draw up a picture of past climates can actually migrate considerable distances, providing false data.


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A team of scientists from the University of Washington has found that many climate signature substances, such as sea salt and sulphuric acid, in ice over 100,000 years old can travel through microscopic channels of liquid water between individual ice crystals. Over time, as the impurities become buried deeper in the ice, where it is warmer and there is more liquid water, the movement becomes more pronounced. The result is that substances found at a depth of 3km (1.9 miles) could be 50cm (20 inches) or more away from where they were originally deposited many thousands of years ago, a distance that accounts for approximately 100 years of snowfall.

“The point of the [research] is to suggest that the ice core community go back and redo the chemistry,” said John Wettlaufer, one of the researchers. “That’s a lot of work, and we’re hoping to be involved in that.”

The researchers now intend to develop models which can help scientists account for the relative movement of different impurities when making their ice core measurements.

“That would be what we most would want to influence – the way people make their observations,” said Wettlaufer. “Since they are doing all that work, they can’t afford to neglect these important physical processes in their interpretation.”

“The ice cores themselves are wonderful records of climate,” said Alan Rempel, and one of the researchers on the team. “Nobody is questioning that.”

The research is published in the May 31 issue of the journal Nature.

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