Ice cover on Lake Superior near-record lows
Posted on: February 21, 2017
Feb 18, 2017 – Lake Superior MODIS satellite imagery showing ice coverage. (Source: https://coastwatch.glerl.noaa.gov/modis/modis.php?region=s&page=1)

Ice cover on the Great Lakes is at a near-record low (<10% coverage vs. 80% in 2015), thanks to the January thaw.  This has been the warmest Superior has been in 16 years, and it has contributed to some of the lowest lake ice coverage on record for this winter season.

As of January 30, the lake ice was only slightly below where it was just one year ago, but less than a third of what was on the water back in 2015.

 

Percentage ice cover for Lake Superior (Winter of 2016-2017) (Source: https://coastwatch.glerl.noaa.gov/statistic/ice/gif/s2016_2017_ice.gif)

 

 

 

 

 

So what does this mean for summer?

This could mean another year of low water levels across the Great Lakes as well as the inland lakes, due to the effects of evaporation.

Evaporation from the lakes is driven by the difference in the temperatures of the water and the air. The higher the water temperature, compared to the air, the greater the amount of evaporation there will be from the lakes.

During a cold winter, with the lakes frozen over, this halts evaporation by putting a barrier of ice between the water and air. Lake effect snows are rare, at best, and even in spring and summer, after the lakes melt, the greater amount of ice results in lower water temperatures, which keeps evaporation to a minimum. Thus, it doesn’t take much rainfall over the lakes to keep water levels higher.

During a warm winter, where lakes are mostly ice-free, these warm lakes with less ice coverage directly result in more evaporation. This contributes to repeated lake effect snowfall events during the colder months, which begin simply by having the winds align properly over the lake surface. Later, as conditions warm during spring and into summer, the lake temperatures tend to stay a step ahead of the air temperatures, which results in stronger evaporation from water surfaces in the warmer months too.

For more information:
The following links provide information on ice coverage currently as well as in comparison to previous years.

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