After a nearly ice-free winter, Lake Erie was filled with swirls of suspended sediment and algae on the first day of spring 2012. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image at 16:25 a.m. Central Daylight Time on March 21, 2012.
Muddy, tan-colored water along the shoreline reveals sediment that has washed out of the rivers and streams that feed the lake. Milky green, light blue, and white shades may also be sediment-rich waters. As the shallowest of the Great Lakes, Erie’s bottom can be stirred up by strong spring winds and the currents they generate. The lake bottom is rich in quartz sand and silt, as well as calcium carbonate (chalk) from limestone.
Warm temperatures this winter meant more rainfall than snow, and more immediate runoff from streams. River flow with sediment was much higher than average for much of the winter, according to NOAA oceanographer Richard Stumpf.
Some patches of green in the water are algae and other forms of phytoplankton. Air temperatures have been well above normal in the region for most of the winter, and particularly in the past week. Since the lake has been mostly clear of ice, algae and other phytoplankton have been blooming for several weeks. By mid-March, water temperatures in Lake Erie were in the upper 30s (Fahrenheit). “Even when ice covered, Lake Erie can get strong winter algal blooms,” wrote Stumpf.