Friday, March 9, 2012

Sharp Decline in Great Lakes Ice Cover over the past Four Decades

I used to call them icebergs. Back when I was a kid. Icebergs on Lake Michigan. Going out as far as you could see. And along the lakeshore, tall tall "ice dunes". "Ice Dunes". It's a word I learned recently. I never knew them as ice dunes. But as ice is pushed ashore by waves, and as the waves themselves crash on the shore and freeze, massive structures form along the lakeshore, known as ice dunes.

I meant to go out and take pictures of the ice dunes and have on occasion traveled down to Lake Michigan with my camera this winter, but the ice dunes were small to non-existent.

In fact, ice cover along the Great Lakes this year was down to about 5% this year. The lowest amount of ice cover on the Great Lakes ever recorded. Ice cover on the Great Lakes has been steadily declining since we started taking records in 1973 when ice covered 93% of the Great Lakes.

Spectral analysis shows that lake ice has both quasi-decadal and interannual periodicities of ~8 and ~4 yr. There was a significant downward trend in ice coverage from 1973 to the present for all of the lakes, with Lake Ontario having the largest, and Lakes Erie and St. Clair having the smallest. The translated total loss in lake ice over the entire 38-yr record varies from 37% in Lake St. Clair (least) to 88% in Lake Ontario (most). The total loss for overall Great Lakes ice coverage is 71%, while Lake Superior places second with a 79% loss.

Yeah, ice cover is cyclical. But the cycles seem to be 4 to 8 years. And it's been dropping steadily.

Winter ice cover on the Great Lakes has dropped dramatically over the past four decades, according to a new report. Peak ice has dropped by 71 percent on average, with Lake Michigan ice decreasing by even more.

Okay. So we're seeing a sharp decline in ice cover over the Great Lakes.

So what?

Wang says losing winter ice can cause a number of problems for the Great Lakes ecosystem. It can speed up wintertime evaporation from the lakes, which could reduce water levels. The trend could also fuel more and earlier algae blooms, which damage water quality and habitat. And it leaves shoreline more exposed to waves, accelerating erosion.

We're looking at drops in water levels due to greater evaporation....disruption of coastal ecosystems....disruptions in shipping.......and earlier algae blooms. Now, when I swim in Lake Michigan there are often these odd balls of algae floating around me, about the size of a pea and hundreds of them. That's a relatively new development.

The world is changing fast.

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