[All] G&M Climate change blamed for Great Lakes decline.

[Richard and Norah Chaloner]

Climate change blamed for Great Lakes decline



Bill Ives of
Waubaushene, Ont., walks along a dock on his waterfront property in
2007. The water levels in Georgian Bay have receded leaving waterfront
properties literally high and dry. The Globe and Mail


Canadian-U.S. study attributes discernible drop in water levels in Huron and Michigan to drier weather
 





Martin Mittelstaedt

>From Wednesday's Globe and Mail
Published on Tuesday, Dec. 15, 2009 8:24PM EST
Last updated on Wednesday, Dec. 16, 2009 3:24AM EST




The water levels of Lake Huron and
Lake Michigan have been falling steadily compared with those on Lake
Erie, and no one knew why.


But a major report financed by the U.S. and Canadian governments
suggests an answer: The fingerprints of climate change are starting to
be found in the Great Lakes, the world's largest body of fresh water,
causing a discernible drop in their levels.


The report, released Tuesday, estimated that Lake Huron and Lake
Michigan have fallen about a quarter metre relative to Lake Erie since
the early 1960s, with 40 to 74 per cent of the reduction due to recent
changes in precipitation patterns and temperatures.


The alteration in climate is “the most significant factor” in the
water level drop and “could be a more substantive issue for the future
on the Great Lakes,” said Ted Yuzyk, Canadian co-chair of the
International Upper Great Lakes Study Board, which compiled the report.


Previous studies have projected a decline in the amount of water in
the Great Lakes due to climate change, but the board is the first to
suggest the trend is already happening.


The fall in water levels is attributed to such factors as less
precipitation and the persistent, long-term decline in the lakes' ice
cover each winter.


The report said generally drier weather and drought-like conditions
from 1998 to 2008 in the central part of North America led to a drop of
about 20 per cent in the quantity of water flowing into Lake Huron and
Lake Michigan, compared with the average since 1948.





The two lakes depend on precipitation and run-off for about
three-quarters of their inflow. The other quarter comes from Lake
Superior, whose outflow can be partly regulated. Lake Erie, by
contrast, receives nearly 80 per cent of its supplies from Lake Huron,
so it hasn't been influenced as dramatically by the reduction in
precipitation.


The finding that climate change is already undermining the Great
Lakes is politically sensitive. The board has written to the Canadian
and U.S. governments to see whether it is within its mandate to study
ways to hold back some of the water in Lakes Huron and Michigan to
maintain their size in the face of global warming. Mr. Yuzyk said the
clarification is still being assessed.


The board was assembled by the International Joint Commission, a
bi-national U.S. and Canadian organization that monitors boundary
waters the two countries share.


The concerns about Lake Huron and Lake Michigan levels arose in
2005, when a Canadian environmental organization, Georgian Bay Forever,
said levels were diminishing because dredging of the St. Clair River in
the 1960s allowed more water to drain from the lakes. The river, which
runs by the Ontario community of Sarnia, drains the two lakes and
ultimately flows into Lake Erie, leading to worries that the Great
Lakes had sprung a leak.


But the report said that while the riverbed experienced some erosion
in the 1980s, it now appears to be stable. In addition, it said a small
part of the observed water level changes were due to the way land
around the Great Lakes is rebounding from the melting of glaciers that
covered the area during the last ice age.


While most of the world's attention on disappearing ice has focused
on the Arctic, the trend is also happening on the Great Lakes. The
report said that in the past 36 winters, three of the four smallest ice
covers on Lakes Huron, Michigan, Erie and Superior occurred from 1998
to 2008.


Less ice leads to increased heat input from sunlight, higher winds
around the water and more evaporation, contributing to lower water
levels.



The report involved more than 100 scientists and engineers and a budget estimated at $4-million.


 		 	   		  
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