John Downing on how to make an ice-out prediction
Downing is a professor of biology and with the Large Lakes Observatory, also serving as the director of Minnesota Sea Grant. His passion — verging on obsession — is determining when ice-out will happen each year.
It’s a question keeping geese, trumpeter swans and dock-owning Minnesotans up at night: when will the lakes open up?
Luckily, John Downing is here to help. Downing is a professor of biology and with the Large Lakes Observatory, also serving as the director of Minnesota Sea Grant. His passion — verging on obsession — is determining when ice-out will happen each year.
With climate change, ice-out has become less predictable, Downing said. Using a combination of factors including snow depth, ice thickness and cumulative heat, Downing developed a series of equations to predict when ice will finally melt. The speed of melting can also depend on the size of the lake and the amount of water flowing into or out of it.
In addition to satisfying curiosity, there are many practical reasons why an ice-out date matters. It's an important date for resort owners, law enforcement can predict an increase in traffic when the lakes are open, and people need to get their cars off the lake well before then.
“What a lot of people don’t realize about (having a vehicle on a lake) is you’re floating your pickup truck on the lake, and you’re using the ice as a boat. It’s not like it’s so strong it can hold your pickup up. It’s a float,” Downing said.
One of the strongest influences on ice-out is cumulative heat, Downing said. If one adds up the number of degrees above freezing over the season, the lake is likely to be open once about 220 is reached. Downing built a widget for this purpose.
To learn more about the science behind his predictions, read his column on the Minnesota Sea Grant website.