After a winter with no ice cover last year, Otsego Lake has returned to normal and is now covered with a coating of four or more inches that is growing thicker each day.

Dr. Willard Harman, director of the Biological Field Station, said Tuesday, Jan. 14, will go down as the official date of the closing for the winter of 2002-03.

Harman said he was out Sunday and there was a solid four inches of ice over the lake.

"It was cold enough this winter that when it froze, it did so completely without any of the small holes which will sometimes remain open for days after the rest of the lake is frozen," he said.

Harman said he has seen ice up to a "couple feet thick," but that in the last few years it has been more likely to be about 10 inches.

Cooperstown has records of the lake's annual closing and opening each winter dating back to the 1840s. The earliest closing appears to be the winter of 1917-18 when ice covered the lake on December 13 and stayed for 122 days until April 14. Although it was the earliest closing, that winter did not record the longest number of days closed. That record is shared by the winters of 1872-73 and 1876-77 when the lake was covered with ice for 131 days. The latest closing - Feb. 25 - happened in successive years, 1932 and 1933.

Although there is some dispute, the winter of 1997-98 is the only other when the lake did not completely freeze over, according to Harman.

Long-time U.S. Weather Service observer Harold Hollis declared the lake closed on February 16, that year - one of the latest dates - but Harman believed there were still open spots in the ice. "We felt there was open water someplace all winter long," he said.

After Hollis' death in 1999, his weather observation station was moved to NYSHA where data such as temperatures and precipitation are still recorded daily, but determining the opening and closing dates for the lake was inherited by Harman and the field station.

Harman explained that in the summer a layer of warm water is on top of colder water toward the bottom of the lake. As the air temperatures cool during the fall, so too, does the water temperature until the warm water at the top is the same temperature of the lower water. When that occurs, all the water in the lake mixes.

"It has to go through the mixing process before it can freeze," Harman said. "The whole lake has to cool to four degrees centigrade."

Water is at its densest at that temperature and is lighter and floats on top if it is either warmer or colder.

"That's what's tricky about it," he said. "Once it gets to 4 degrees centigrade, anything more floats on top. This is complex business."

To declare the lake officially closed, there can be "literally no open water anywhere," Harman said. There is also another date the field station tracks that is ecologically more important. And that is when the lake freezes and is functionally closed even though there may be one or more holes which can remain open for weeks.

"It's more important from the point of view of the biology of the lake," he said. He added that they have been thinking about starting to include both dates when they talk about the lake freezing over.