By Mark Johnson of the Journal Sentinel
Sept. 24, 2012
This summer the ice melt over the Arctic Ocean surpassed the previous record set in 2007 and did so by a wide margin, an area larger than the state of Texas.
What this will mean for Wisconsin isn’t entirely clear, though University of Wisconsin-Madison scientist Steve Vavrus said he expects a slower jet stream, which could result in more persistent extreme weather – longer freezes and longer heat waves.
“This probably is a new normal,” Vavrus said, looking back on the last six years, which have been marked by a string of significant ice melts. “In 2007, nobody could even believe how much ice was lost that year and then the year after that was almost as much.”
As bad as 2007 was, this year’s melt was 18% worse.
“Not only did we break a record this year, but we broke it by a lot,” said Vavrus, a senior scientist in the Nelson Institute Center for Climatic Research at UW. The melt was significant enough to be visually apparent in the satellite images taken of the ocean.
Less ice means less insulation protecting the cooler overlying atmosphere from the warm ocean. This in turn lowers the temperature differences between the polar regions and the warm tropics, Vavrus said.
Other possible consequences of a reduced ice cover are variations in snow cover in Siberia and temperature shifts in the tropics.
The melting of the Arctic Ocean ice typically finishes for the season in mid-September. As the weather grows colder the ice grows back. But Vavrus said the seasonal recovery has not been as significant in recent years.
“It’s not completely growing back like it used to in the winter,” he said.
There is a time lag usually between the end of the ice melt over the Arctic and the time at which Wisconsin begins to feel the effects.
“We’ll be keeping a close eye on how the circulation behaves to see if there is a linkage between this incredible ice melt and the weather (in Wisconsin) in fall and winter,” Vavrus said.