Arctic Sea Ice 50% Lower in the Past

Ronald Bailey – Reason.com August 5, 2011

A new study in Science this week by Danish researchers analyzing ancient driftwood finds that Arctic sea ice coverage has been substantially lower than it is today in the past 10,000 years. From Eurekalert:

For the last 10,000 years, summer sea ice in the Arctic Ocean has been far from constant. For several thousand years, there was much less sea ice in The Arctic Ocean – probably less than half of current amounts. This is indicated by new findings by the Danish National Research Foundation for Geogenetics at the University of Copenhagen…

Team leader Svend Funder, and two other team members and co-authors of the Science article, Eske Willerslev and Kurt Kjær, are all associated with the Danish Research Foundation at the University of Copenhagen.

Regarding the research results, Funder says, “Our studies show that there have been large fluctuations in the amount of summer sea ice during the last 10,000 years. During the so-called Holocene Climate Optimum, from approximately 8000 to 5000 years ago, when the temperatures were somewhat warmer than today, there was significantly less sea ice in the Arctic Ocean, probably less than 50% of the summer 2007 coverage, which was absolutely lowest on record. Our studies also show that when the ice disappears in one area, it may accumulate in another. We have discovered this by comparing our results with observations from northern Canada. While the amount of sea ice decreased in northern Greenland, it increased in Canada. This is probably due to changes in the prevailing wind systems. This factor has not been sufficiently taken into account when forecasting the imminent disappearance of sea ice in the Arctic Ocean.” …

“Our studies show that there are great natural variations in the amount of Arctic sea ice. The bad news is that there is a clear connection between temperature and the amount of sea ice. And there is no doubt that continued global warming will lead to a reduction in the amount of summer sea ice in the Arctic Ocean. The good news is that even with a reduction to less than 50% of the current amount of sea ice the ice will not reach a point of no return: a level where the ice no longer can regenerate itself even if the climate was to return to cooler temperatures. Finally, our studies show that the changes to a large degree are caused by the effect that temperature has on the prevailing wind systems. This has not been sufficiently taken into account when forecasting the imminent disappearance of the ice, as often portrayed in the media,” Funder says.

In addition to giving us a better understanding of what the climate in northern Greenland was like thousands of years ago, it could also reveal how polar bears fared in warmer climate. The team plans to use DNA in fossil polar bear bones to study polar bear population levels during the Holocene Climate Optimum.

In other news, Bloomberg is reporting today that Arctic sea ice melted rapidly in July:

Arctic sea ice, a benchmark for the earth’s rising temperature, may approach a record low in September after its biggest July melt since 2007, researchers at the U.S. National Snow and Ice Data Center said.

Ice covered an average of 7.92 million square kilometers (3.06 million square miles) of ocean last month, 210,000 square kilometers less than the average for the same period in 2007, when there was a record melt season, according to the center. After a recovery toward the end of the month, an all-time low is “an outside possibility,” said Walt Meier, an NSIDC scientist.

“It will be another low year, very likely one of the five lowest,” Meier said today in an e-mail. “One year doesn’t say too much in and of itself, but the long-term downward trend and the series of very low years is indicative of a thinner ice cover and warming temperatures.”

The Arctic ice typically melts until September, before freezing again through March. Scientists at the Boulder, Colorado-based center say the declining ice pack is a harbinger of global warming. By 2030, there may “consistently” be summers where little or no ice remains on the ocean, Meier said.

However, the BBC notes that Funder and his fellow researchers are a bit less concerned about the imminent fate of Arctic sea ice:

Dr Funder and his team say their data shows a clear connection between temperature and the amount of sea ice. The researchers concluded that for about 3,000 years, during a period called the Holocene Climate Optimum, there was more open water and far less ice than today – probably less than 50% of the minimum Arctic sea ice recorded in 2007.

But the researcher says that even with a loss of this size, the sea ice will not reach a point of no return.

“I think we can say that with the loss of 50% of the current ice, the tipping point wasn’t reached.”

The idea of an Arctic tipping point has been highlighted by many scientists in recent years. They have argued that when enough ice is lost it could cause a runaway effect with disastrous consequences.

“I don’t say that our current worries are not justified, but I think that there are factors which will work to delay the action in relation to some of the models that have been in the media.

“I think the effect of temperature and global warming may cause a change in the general wind systems which maybe will delay the effects of the rapidly rising temperatures a little bit.”

Interesting. Very interesting.

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