Tuesday, January 8, 2013

The Influence of Climate Change on Lake Superior

The information included in today's blog posting is in a movie that I created yesterday for the online rockhounding adventures.  In segmenet C of the second adventure, I describe how ice flows on Lake Superior transport rock around the lake basin.  As part of the research, I was curious whether winter ice  coverage has changed over the years.  I must admit that I was astonished when I took a look at some of the long term trends.

When it comes to climate change, the Great Lakes are considered by some to be the "canary in the coal mine."

The trends since the 1970s have been especially dramatic.

Ice coverage on Lake Superior has declined 79 percent since 1973.

During the winter of 2012, the lake had only 5 percent ice coverage.

This was the second lowest total ever behind 2002.  Below are two videos compiled by the Great Lakes Environmental Research Laboratory for ice coverage in 2002 and 1979.  Both show the ice cover between December and May.  The difference in ice cover is dramatic.   NOTE:  In the online rockhounding adventure movies I was able to double the speed of this movie clips.  Also, the video processor associated with the blogger software leaves a bit to be desired.  The quality in the online rockhounding adventure is much better.


A similar decline of ice cover has been reported on lakes throughout North America, Europe, and Asia.

There are several factors that have combined to limit the ice formation. 

The average winter air temperature over Lake Superior has increased 5.0 F (2.7 C) since 1973.

The average water temperature increased 4.5 F (2.5 C) between 1979 and 2006.

For the past 60 years, the average amount of annual precipitation in the Lake Superior region
has declined.  More than half the U.S. is currently in a drought, including the Lake Superior region.

In addition, over the past few decades wind speeds have increased almost 30 percent.

Evaporation rates have intensified 17 percent.

As a result, the level of Lake Superior is approaching the all-time record low.

Other climate change trends include:
-- Hotter summers and warmer winters.
-- Shorter winters and longer summers.
-- More mid-winter rain rather than snow.
-- More frequent and intense storms.

But the good news for agate hunting is that Lake Superior's lower level exposes more rock.

Even though there is less ice to bring new rock to our beach, there is still a 10,000 year supply of rock
just waiting to dance with the waves and be found by rockhounds who appreciate their beauty.

Reference cites:
NASA / Jeff Schmaltz, MODIS Rapid Response Team, GSFC
NOAA video http://www.glerl.noaa.gov/data/ice/atlas/daily_ice_cover/animations/animations.html
NOAA http://www.crh.noaa.gov/images/mqt/mar5_2010_big.jpg 2010
NASA / NOAA / NASA map by Robert Simmon image
EPA http://www.epa.gov/climatechange/images/impacts-adaptation/LakeSuperiorSummerTemp.gif
EPA http://www.epa.gov/climatechange/impacts-adaptation/water.html and
U.S. Army Corps of Engineers, 
Wiki / The Odd Gitt

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