2/14/14, "Great Lakes become nearly covered with ice,"
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| 2/12/14 |
From the bridge of the
Coast Guard cutter Mackinaw, northern Lake Huron looks like a vast,
snow-covered field dotted with ice slabs as big as boulders - a
battleground for the icebreaker's 58-member crew during one of the
roughest winters in memory.
It's been so
bitterly cold for so long in the Upper Midwest that the Great Lakes are
almost completely covered with ice. The last time they came this close
was in 1994, when 94 percent of the lakes' surface was frozen.
As
of Friday, ice cover extended across 88 percent
, according to the
federal government's Great Lakes Environmental Research Laboratory in
Ann Arbor.
Sections of the lakes, which hold
nearly one-fifth of the freshwater on the world's surface, harden almost
every winter. That freezing keeps the Coast Guard's fleet of nine
icebreakers busy clearing paths for vessels hauling essential cargo such
as heating oil, salt and coal. But over the past four decades, the
average ice cover has receded 70 percent, scientists say, probably in
part because of climate change.
Still, as this
season shows, short-term weather patterns can trump multi-year trends.
Winter arrived early and with a vengeance and refuses to loosen its
grip.
"That arctic vortex came down, and the ice just kept going," said George Leshkevich, a physical scientist with the federal lab.
The
deep freeze is more than a novelty. By limiting evaporation, it may
help replenish lake water levels - a process that began last year after a
record-breaking slump dating to the late 1990s....
Buffalo, N.Y, got nearly
43 inches of snow in January, but this month just 13 inches have fallen,
a decline resulting largely from the freeze-over of Lake Erie even
though Lake Ontario has remained largely open, said forecaster Jon
Hitchcock of the National Weather Service.
Heavy ice can also protect fish eggs from predators, and it has delighted photographers, ice anglers and daredevil snowmobilers.
At
Apostle Islands National Lakeshore in Wisconsin, the rock-solid cover
has allowed around 35,000 visitors to trudge miles over Lake Superior to
explore caves featuring dazzling ice formations. It's the first time in
five years the lake surface has been firm enough to allow passage.
With
no letup in the cold, the ice hasn't experienced the usual
thaw-and-freeze cycle, so nature's artistry is even more delicate and
beautiful, with needle-like hoarfrost crystals sprinkled across sheets
that dangle from cave ceilings like giant chandeliers....
For
Coast Guard icebreaker teams, it's all business. They've logged four
times more hours this season than the average for the same period in
recent years, said Kyle Niemi, spokesman for the agency's Cleveland
district headquarters.
The 240-foot Mackinaw
began its duties Dec. 16 - several weeks earlier than usual - and worked
nonstop until Feb. 8, when traffic slowed enough to allow a break.
"As
you can imagine, the crew's tired," Cmdr. Michael Davanzo said this
week during a tour of the ship in its home port of Cheboygan.
A
35-year Coast Guard veteran who has spent 12 years on the lakes,
Davanzo said this winter is the toughest he's experienced because the
ice came so soon and is so thick and widespread, and the weather has
been constantly bitter.
The Mackinaw,
commissioned in 2006 to replace an older vessel with the same name, is
designed specifically for duty on the Great Lakes. It's propelled by two
"Azipod" thrusters that can spin 360 degrees and fire jets of water at
adjacent ice, weakening it. Sometimes the crew will drive the ship's bow
onto an ice sheet to crack it with sheer weight. Or they'll go
backward, chopping up ice with the propeller blades.
When
the going gets tough, there's the battering-ram option - hurling the
reinforced hull directly against walls of ice that can be several feet
thick.
The workload typically drops sharply
after navigational locks on the St. Marys River, the link between Lakes
Superior and Huron, close in mid-January and most large cargo haulers
dock for winter. But the ice was so thick this year that a number of
freighters were still struggling to complete final deliveries days
later. Even now, demand for road salt and heating oil in the Midwest is
keeping some icebreakers busy.
One day last
month, the Mackinaw spent 16 grueling hours helping a freighter squeeze
through a narrow 3.5-mile section of the St. Marys. As the Mackinaw
attacks the ice, the engines roar and the ship vibrates. The noise and
motion are "like living in an earthquake 16 hours a day," Petty Officer
3rd Class Ryan Alderman said.
Davanzo hopes
for rain and warmer temperatures that would melt some ice before the
locks reopen in late March, when the Mackinaw will venture onto Lake
Superior and clear paths for iron ore and coal haulers....
Despite
the inconvenience, there's a silver lining for shippers. Since the
low-water period began in late 1990s, they've been forced to carry
lighter loads to avoid scraping bottom in shallow channels and harbors.
Heavy snow and rain in 2013 finally raised water levels.
Ice
cover blocks evaporation, the leading cause of low water. It also will
keep the lakes cooler for a longer time this year, delaying the onset of
heavy evaporation season, scientist John Lenters reported in a paper
last month, although the benefit is partially offset by stepped-up
evaporation shortly before the ice forms.
In
Lake Superior, snowbound Isle Royale National Park is home to a
dwindling and inbred wolf population that is usually trapped on the
island. Biologists hope a newcomer or two will venture to the park now
that the lake is almost entirely frozen over. The park's first wolves
are believed to have crossed an ice bridge from Canada, 15 miles away,
in the late 1940s."...via Drudge
.
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