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.