More good news about the cold weather
The extreme cold may help raise
water levels in the Great Lakes, protect shorelines and wetlands from
erosion, kill insect pests and slow the migration of invasive species.
TRAVERSE CITY, Mich.
— From a field station in northern Wisconsin, where the previous
night's low was a numbing 29 degrees below zero, climate scientist John
Lenters studied computer images of ice floes on Lake Superior with
delight.
It may be hard to think of this week's deep freeze as
anything but miserable, but to scientists like Lenters there are silver
linings: The extreme cold may help raise water levels in the Great
Lakes, protect shorelines and wetlands from erosion, kill insect pests
and slow the migration of invasive species.
Related: Arctic air eases its grip on much of the U.S.
"All around, it's a positive thing," Lenters, a specialist in the climate of lakes and watersheds, said Wednesday.
Ice
cover on the Great Lakes has been shrinking for decades, but this year
more than 60 percent of the surface is expected to freeze over at some
point — an occurrence that could help the lakes rebound from a prolonged
slump in water levels.
AP Photo: West Bend Daily News, John Ehlke, File
In
this June 22, 2011 file photo are tracks from Emerald Ash Borers left
in a black ash tree outside the Riveredge Nature Center in Newburg, Wis.
Even
agriculture can benefit. Although cold weather is generally no friend
to crops, some of southern Florida's citrus fruits can use a perfectly
timed cool-down, which they were getting as midweek temperatures hovered
around freezing.
"A good cold snap lowers the acidity in oranges
and increases sugar content, sweetens the fruit," said Frankie Hall,
policy director for the Florida Farm Bureau Federation. "It's almost
been a blessing."
Scientists noted that subzero temperatures and
pounding snowfalls like those that gripped much of the nation for
several days are not unheard-of in the Midwest and Northeast and used to
happen more frequently.
For all the misery it inflicted, the
polar vortex that created the painfully frigid conditions apparently
broke no all-time records in any major U.S. cities, according to Jeff
Masters, meteorology director of Weather Underground.
"I'm just
happy to see that we have a normal winter for once," said Lenters, who
works for Limnotech, an environmental consulting firm in Ann Arbor.
As the climate has warmed, the absence of bitter cold has actually been damaging.
The
emerald ash borer, an insect native to Asia, arrived in the U.S. around
2002 and has killed about 50 million ash trees in the Upper Midwest.
But some locales this winter may have gotten cold enough to kill at
least some larvae, said Robert Venette, a U.S. Forest Service research
biologist in St. Paul, Minn.
AP Photo: Suzette LaBoy
In this Jan. 7, 2014 image from video Diane Cordeau poses for a photos on her Kai-Kai farm near Indiantown, Fla.
A
reading of minus 20 will usually produce a 50 percent mortality rate,
and "the numbers go up quickly as it gets colder than that," Venette
said.
While the freeze won't wipe out the ash borer, it will give
communities a chance to develop plans for limiting the bug's spread, he
said.
Other pests that originated in warmer places could be
affected as well, including the gypsy moth, the hemlock woolly adelgid
and the European beetle that carries Dutch elm disease, said Lee
Frelich, director of the University of Minnesota Center for Forest
Ecology. Native insects have evolved to cope with deep freezes.
Extreme
cold also reins in invasive nuisance plants such as kudzu, which has
ravaged the Southeast but has yet to find its way north, said Luke Nave,
a University of Michigan assistant research scientist.
"As long
as these cold snaps continue to occur, they will help reinforce the
current range limits for certain plants," Nave said.
Water levels
have been below normal in most of the Great Lakes since the late 1990s
because of high evaporation and occasional lack of rain and snow. A year
ago, Lakes Michigan and Huron hit their lowest points on record. Cargo
ships were forced to carry lighter loads to avoid running aground in
shallow channels. Marinas lost business and wetlands dried up.
But
levels rose sharply in 2013, thanks to heavy snow and rain. Extensive
ice cover this winter could help the lakes continue their recovery. The
National Oceanic and Atmospheric Administration's Great Lakes
Environmental Research Laboratory in Ann Arbor predicts ice will cover
57 to 62 percent of the surface waters.
One of the lab's
climatologists, Jia Wang, previously reported that the lakes' ice cover
has declined 71 percent over the past 40 years. He said this year's
showing may be a short-lived exception to an ongoing trend.
AP Photo: Granite Island Light Station LLC
In
this image from video provided by the Granite Island Light Station LLC,
ice covers the water surrounding Granite Island in Lake Superior
Wednesday, Jan 8, 2014 near Marquette, Mich.
But this year's
bone-chilling conditions could keep water temperatures low well into
the summer, delaying the seasonal warming that triggers heavy
evaporation, Lenters said.
The deep freeze also has piled up ice
along Great Lakes shorelines, providing a buffer that will prevent heavy
waves from eroding soil and disturbing wetlands.
Sections of the
lakes that freeze solidly create new pathways for wandering wildlife.
That could help gray wolves, which have spread across Michigan's Upper
Peninsula, find new territory in the Lower Peninsula, where the
occasional straggler has turned up but no established packs are known to
exist.
"You can decide for yourself whether that's a good thing,"
said Philip Myers, curator of mammals at the University of Michigan
Museum of Zoology. "I think it is."
AP
Associated Press writers Steve Karnowski in Minneapolis and Seth Borenstein in Washington, D.C., contributed to this report.