On Feb. 19, 2014 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite flew over the Great Lakes and captured this striking false-colored image of the heavily frozen Great Lakes – one of the hardest freeze-ups in four decades. According to the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL), ice cover on North America’s Great Lakes peaked at 88.42% on Feb. 12-13 – a percentage not recorded since 1994. The ice extent has surpassed 80% just five times in four decades. The average maximum ice extent since 1973 is just over 50%. Unusually cold temperatures in the first two months of the year, especially in January, are responsible for the high ice coverage. Very cold air blowing over the surface of the water removes heat from the water at the surface. When the surface temperature drops to freezing, a thin layer of surface ice begins to form. Once ice formation begins, persistently cold temperatur...