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The
recent Arctic blast gripping the nation will likely contribute to a rise in
Great Lakes water levels in 2014, new research from the University of Michigan
and Michigan State University shows. Research conducted by the two schools
through the Great Lakes Integrated Sciences and Assessments Center (GLISA) shows
the correlation between periods of high and low evaporation and its effect on ice
cover. Years with high ice cover were usually followed by cooler summer water
temperatures and lower evaporation rates, but these same high-ice winters were
preceded by high evaporation rates during the autumn and early winter indicating
a two-way connection between ice cover and evaporation. While ice cover reduces
evaporation from what would otherwise be exposed lake surface water, it also reduces
lake temperature generating ice cover.
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The findings carry numerous
implications for the short-term variation and long-term trend of Great Lakes
lake levels, which have been declining since the early 1980s and have been at a
sustained low for several years. What’s more, Lake Superior underwent a regime
shift during the late-1990s El Niño event, resulting in warmer summer water
temperatures and winters with less ice cover. Given the long-term trend of
warming lake temperatures, it’s unclear if the lakes will ever return to
previous conditions.
These results
could help decision-makers define the risk associated with climate conditions affecting
evaporation and water levels. “It’s our hope that we will soon have the
funding and infrastructure in place to maintain — and even expand — the network
well into the future,” said John Lenters, the study’s lead investigator.
“This will be extremely important for improving Great Lakes water-level
forecasting and for understanding the long-term impacts of climate
change.”
Evaporation
is a dominant physical process affecting the Great Lakes reaching 0.4-0.6
inches of release per day. To put this in perspective, a single day’s loss of
0.5 inches of water from surface area of the Great Lakes is roughly 20 times
the amount of water that flows over Niagara Falls.
Despite
its critical role, evaporation has been challenging to understand. For example,
one might assume that the Great Lakes’ highest rates of evaporation occur in
the summer, but this is not the case. The highest evaporation rates typically
occur in late fall and early winter, when the difference in air temperature and
water temperature is greatest. Because the lake was 30 to 40 degrees warmer than
the overlying air in early January of 2014, the temperature contrast led to
high evaporation rates and significant lake effect snowfall, defying
expectations.
Read
more at the Great
Lakes Integrated Sciences and Assessments Center.
Broken
Ice at Sunrise image on Lake Superior by Jacob Clausnitzer via
Shutterstock.
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