Ice Fishing Hanging on in Central Iowa

Ice fishing this time of year can be very hit or miss. Ice thicknesses are beginning to vary widely across the state as our spring-like sun is gaining intensity.

Image Courtesy MDNR

Although warm weather is approaching and ice may become dangerously thin, I expect ice thicker than 3" to hang on. Using a model I put together based on ice growth processes, it appears fishable ice may remain in central Iowa for at least two more weeks. With that said, dangerous ice conditions are likely to develop this weekend.

Average to above average temps in the forecast this week.

This year anglers have been blessed with more ice than last year (which isn't saying much) but temps in the 40s signal the end is near. Temps will continue to warm on average through the weekend and could stay above freezing deteriorating ice conditions through Valentine's day.

Ice growth chart courtesy fishingvermont.net

Ice growth and melting is a very complicated process. The biggest factors on ice growth are the average air temperature, the thickness of the ice, snow cover, water currents, sun intensity, fish schooling and waterfowl. In order to grow, ice has to use energy to freeze water into solid form. Initially, skim ice can freeze and grow very quickly. As the thickness increases it takes more energy to transfer the heat/cold through the system because some energy is lost along the way. The result is; the thicker the ice - the longer periods of cold are required to freeze the water below. Slower growing ice is often clear and very strong. Fast growing ice is full of trapped air bubbles which makes it weaker.

Ice growth chart
 courtesy http://lakeice.squarespace.com/ice-growth/

Snow cover can insulate the ice, protecting it from the harsh cold and preventing it from thickening. Water currents on rivers or convective currents in lakes can erode ice in localized spots resulting in potentially dangerous weak spots. Schools of fish and waterfowl can also "stir" up the water causing weak spots and maintaining open water.

Caught on Twelve Mile Lake 1-21-13. Thanks Cindy McNamara.

As the sun angle increases, and our sunshine becomes more intense, ice conditions will begin to be vary even more than they do now. South facing shorelines will heat up above and below the waterline. Humps and underwater reefs, trees and other shallow structure will begin to absorb sunlight and create daily weak currents of warmer water that will melt the ice from below. Eventually the ice will break apart and ice fishing season will be over.

The good news is, that may not happen until the end of the month here in central Iowa. I put together a crude, empirical model of ice growth and decay for central Iowa. If the forecast holds, we'll lose 1.5" to 3.5" of ice by Valentine's day. Dangerous ice conditions may develop between the 10th and 14th in southern and central Iowa where thickness may thin down to 3" or less.

Actual temps through Feb 5th, forecast temps after that.

After the 15th, an Arctic air mass will spill down from northern Canada and temps will chill into ice-making territory again. This could save the day for ice anglers in central Iowa by rebuilding some ice and prolonging the season another week.