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EarthSky // Earth, Science Wire Release Date: Feb 27, 2014

Great Lakes are mostly frozen

Ice cover on North America’s Great Lakes reached 88 percent in mid-February 2014, levels not observed since 1994.

EarthSky Facebook friend Alan F. Mitan Jr. posted this image this week of ice on Lake Erie.  Thank you, Alan!

EarthSky Facebook friend Alan F. Mitan Jr. posted this image this week of ice on Lake Erie. Thank you, Alan!

Image credit:  NOAA Wisconsin Sea Grant

Ice cover on North America’s Great Lakes reached 88 percent in mid-February 2014 NOAA posted this photo on February 27, 2014 of ice buildup on Lake Michigan along the shore near Manitowoc, Wisconsin. Image via NOAA Wisconsin Sea Grant

Image credit: NASA

NASA’s Aqua satellite acquired this image on February 19, when ice covered 80.3 percent of the lakes. This false-color image uses a combination of shortwave infrared, near infrared, and red (MODIS bands 7-2-1) that helps distinguish ice from snow, water, and clouds. Ice is pale blue (thicker ice is brighter), open water is navy, snow is blue-green, and clouds are white or blue-green (depending on temperature and composition). Image via NASA.

Ice cover on North America’s Great Lakes reached 88 percent in mid-February 2014, levels not observed since 1994. The average maximum ice extent since 1973 is just over 50 percent. It has surpassed 80 percent just five times in four decades.

Nathan Kurtz, cryospheric scientist NASA’s Goddard Space Flight Center, said:

Persistently low temperatures across the Great Lakes region are responsible for the increased areal coverage of the ice.

Cold air and winds remove heat from the fresh water until it reaches the freezing point, at which point ice begins to form on the surface. Kurtz added:

Low temperatures are the dominant mechanism for thickening the ice, but secondary factors like clouds, snow, and wind also play a role.

Scientists say that there was an early ice season this year, owing to cold temperatures in the fall and early winter. Ice was reported on bays and harbors of the Great Lakes as early as the end of November, as opposed to the normal timing of mid-December.

Bottom line: Ice cover on North America’s Great Lakes reached 88 percent in mid-February 2014, levels not observed since 1994.

Read more from NASA Earth Observatory