By Kim Palmer
CLEVELAND, March 7 (Reuters) - The Great Lakes saw some of their worst ice cover in nearly four decades because of a frigid winter with months of below-freezing temperatures in large sections of the northern United States, the National Ocean and Atmospheric Administration said.
As of Thursday, 92.2 percent of the five lakes were under ice, breaking a record set in 1973 but still short of the 94.7 percent set in 1979, the federal agency said.
The area under ice this winter covered about 86,000 square miles, which is a little bit larger than the state of Minnesota.
With a spring thaw approaching and temperatures warming, the 1979 record appears poised to stand for at least another year.
"We had lots of ice on the lakes early this year and then with the polar vortex at the end of December, we saw the ice continue to grow," said George Leshkevich, a physical scientist with NOAA's Great Lakes Environmental Research Laboratory.
Four of the Great Lakes are more than 90 percent under ice, according to Leshkevich, something that has not happened since 1994. The 40-year average ice coverage for all the lakes is about 51 percent, the NOAA said.
The lone hold-out, Lake Ontario, has only 59 percent ice coverage because of its depth and smaller surface. The relatively shallower Lake Erie was 96 percent iced-over, it said.
With the increased ice coverage, the Coast Guard spent more time than usual rescuing snowmobilers who had ventured out onto the frozen surfaces, Coast Guard Petty officer Levi Read said on Friday.
Ice-breaking crews have been working almost non-stop helping to keep commercial waterways clear, with transport time increasing greatly because of the limited passage, Read said.
"We had a truck fall through the ice this year, but no one was in the truck at the time," Read said. (Writing by Jon Herskovitz; editing by Gunna Dickson)