Nature Notes: For one Minnesota ice-out tracker, this has been one interesting spring
Ive been chasing lake ice-outs in Minnesota for 40 years through direct observation, reaching out to people who live near the water and my WCCO Radio (830 AM) program. This spring has been one to remember.
Winterlike temperatures lasted well into April for all of Minnesota. Plus much more than normal snowfall hit the south the first half of April. Many lake ice-outs have been running about three weeks behind normal.
The ice-out phenomenon begins with ice retreating from the shore, creating a belt of open water around the lake with a temperature of about 45 degrees. A wide band of ice beyond the open water then becomes soft and rotten while the rest of the ice cover turns dark.
The main ice sheet eventually weakens and begins to fracture when winds become strong enough to move it. Then ice crystals on the edges of the floating sections begin melting rapidly. Eventually wind will sweep the last ice sheets.
Some loose ice along a shore doesnt constitute the condition of ice still being in, because a boat can easily be pushed through it. I consider ice-out to have occurred when at least 90 percent of the lake is ice-free. I share my ice-out updates with the Department of Natural Resources State Climatology Office.
The ice on Lake Minnetonka, the metro areas largest lake, officially went out May 5. The date was 21 days later than the median, April 14.
Some of the bigger lakes Up North may not be ice-free by the fishing opener Saturday. Best to call ahead.
Jim Gilbert taught and worked as a naturalist for 50 years.