Lake Mendota’s Spring Thaw Ties for 2nd Earliest on Record

Lake Mendota is open for 2017. Photo: Adam Hinterthuer

Yesterday morning I brought breakfast to my daughters at our dining room table, glanced out the window and did a double take. The waters of Lake Monona were a churning mass of brownish bluish green. What had only the night before been a flat sheet of late-winter ice had disappeared, broken up by the unusually strong winds that had persisted overnight.
An unseasonably warm February had already sent the edges of the ice into retreat, leaving strips of open water along the shallow bays, but it took a good, extended gust to really get the ice moving and breaking up. We had a similarly windy ice off in 2013, when high winds blew straight at our building for a few days and piled ice up on the Lakeshore Path. While this year’s ice off may have been a little less dramatic, it is still notable in that, well, we’re starting to say this more and more – it was way earlier than the normal (or in scientific lingo, the “median”) date.
When I got into work today, Lake Mendota looked much like Monona had – and, in fact, the Wisconsin State Climatology Office had announced their official “ice off” dates as the same day – March 7th.
For Lake Mendota, that is tied with the second earliest ice-off in recorded history. It is nearly a month earlier than the median ice-off date of April 4th. All told, from the freeze (or ice-on) date of January 1st, to yesterday’s thaw, Lake Mendota spent 65 days with its ice cap on in 2017, which is one of the ten shortest such spans since 1855. Six of those ten short-duration ice cover seasons have occurred in the last twenty years of the 161-year dataset.
While climate change continues to be debated in statehouses across our country, its impacts are already being written in our long-term lake ice records. Wisconsin is getting warmer. The unusual is getting usual. And earlier open water is simply becoming the new normal.
Welcome to the new normal: Lake Mendota’s blowing in the wind. In March. Photo: Adam Hinterthuer