By mid February, ice coverage of the Great Lakes was at 87.3 percent, as scientists predicted that it would reach record proportions--- more than 94.7 percent--- before the spring thaw.
That can be bad for commercial navigation. But in general, the ice is good for the lakes and their fisheries.
“When you have more ice formation, you have less direct contact with the atmosphere, less opportunity for evaporation and that keeps the water levels up, said Alan Steinman of the Annis Water Resources Institute.
For years now, the lakes have suffered from low water, with Lake Michigan falling to record lows just last year. More water retained will mean more shoreline habitat later.
Yet that also could mean the loss of wetlands gained during the low-water years. From 2004 to 2009, wetlands increased by 13,610 acres in the eight-state Great Lakes region, according to the U.S. Fish and Wildlife Service.
That was the only portion of the country to show an increase, as the rest of the nation’s coastal wetlands shrank by 360,720 acres.
Before ice coverage started reaching record proportions, Donald Uzarski of the Institute of Great Lakes Research explained how the increase occurred.
“As the shoreline moves away from the upland, the wetland essentially follows it,” he said.
“Usually, the amount of wetlands stays the same over the years as water levels rise and fall because wetlands move where the shoreline is. But we’re seeing low levels that have rarely happened in the past.”
Going into spring, water levels likely will be higher than they would have been following a mild winter, thanks to that ice coverage. It increased from 77 to 87.3 percent during the second week of February and was forecast to reach the highest percentage since records started being kept in 1973. Coverage of 94.7 percent was recorded on Feb. 19, 1979.
By Feb. 12, Lake Superior, the most northern of the lakes, was at 95.3 percent coverage. It last was 100 percent ice covered in 1996.
Climate for Lake Erie is a bit milder, but the lake also is shallow compared to its counterparts, meaning it is more likely to freeze in winter. It was at 95.9 percent, on its way to the full coverage that also occurred in 1973, 1978, 1979, and 1996.
By contrast, coverage of Lake Ontario was just 32 percent. One reason for that, scientists theorize, is that the lake doesn’t freeze as easily as the rest because it has a greater capacity for “heat storage.” In other words, it is deep, like Superior, but has far less surface area, where the heat is lost. Also, moving water from Niagara Falls helps keep ice from forming.