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From ice to open water

Blog by: David Coulson , CO 1/14/2014

A few weeks back I wrote a blog stating that once a lake/pond freezes over it takes more than a a day or two of warm water for the ice to go away. That is due to the fact that it takes 80 times as much energy to turn to water to ice or vice versa as it does to heat the same amount of water one degree Celsius.  

When it comes to lakes going from ice to open water, warm temperatures are only part of the story.  There can be several other factors involved that can change the situation faster than temperature alone. 

Many of the “lakes” we fish are reservoirs. Front Range and eastern reservoirs are often irrigation reservoirs.  What that means is they draw down throughout the summer into the fall, and then fill in the winter and spring during ice fishing season.  When an iced over reservoir fills, it lifts the ice cap away from the shore. During freezing cold periods, the edges quickly freeze and there’s little issue, but when conditions are warm, the edges may have thin or no ice.

When the snow has melted, those relatively dark, vegetation free shorelines absorb solar energy faster than the ice (which tends to reflect the sunlight). This can warm and melt the edges of the ice cap faster than the main reservoir ice.  Again, this creates potentially thin ice near shore.

There’s also a property of ice that many forget about, it can sublimate.  That means the ice can transform to water vapor directly without having to melt.  So throughout the winter the ice cap is being lost, although under freezing conditions ice forms far faster than it’s lost.  Even under warming conditions it’s not a major issue.

Why bring it up then?  Well, there’s a wild card, the wind.  When we have high winds, as of late, the air turns over quickly expediting sublimation. Rather like the fan you use in your car to move the air over the heating coils to warm the vehicles space.  The car would warm without the fan, but moving the air speeds up the process.

The wind also plays a second role.  If the shoreline melts and produces some open water, the wind can start pushing the ice cap around.  When the ice is pushed against a shore it can get broken up which expedites the melting process by creating more exposed ice surface. Given enough open water and strong winds, waves can form breaking up the ice even faster.  I remember one year when Wellington #4 went from a fishable ice cap to completely ice free in January after a couple days of 70 mph winds.

One April, years back, I decided to head to the high country for some late season ice fishing.  Arriving at the reservoir, I noted there were a couple inches of “open” water along shore.  No issue, as once I stepped over it, I took a couple steps and drilled a hole.  After six inches of what I judged to be solid ice I headed out and fished. The ice turned out to be a good 18 inches thick and I didn’t give any thought to the breezy weather. That afternoon I walked back to the truck only to find over ten feet of open water between me and the shore. I ended up walking across to the other side of the small reservoir where I found the ice close enough to the shore to get off it.  An hour or so later I made it back the truck.  I was lucky.

My hope is that everyone will think about how temperatures, reservoir behavior (such as when they fill), and how winds may impact ice conditions. Add to that an understanding of how to be safe on the ice as outlined in Tiny Stevens recent article and you’re more likely to make good decisions ice fishing.

Have fun and be safe.

Blog content © David Coulson
Blog Comments
anglerwannabe, 1/14/2014 8:44:27 AM
See every time I consider ice fishing, someone posts something like this or how they fell through!
David Coulson (Flyrodn), 1/14/2014 9:10:15 AM
Ice fishing is a lot of fun, as is fishing. But any time we're around water, liquid or frozen we put ourselves at risk. I don't know the number of deaths/days fishing or the number of deaths/days on the ice. But I'd guess ice is lower. I don't think ice fishing is any more dangerous than any other form of fishing, but there are risks. Point is dangers are involved when ever we fish and with some thought and a little caution we can enjoy the sport and minimize the risks.
opencage, 1/14/2014 3:50:11 PM
That story about losing the shore ice is a good one. Never would have thought about that, thanks OG. After you're done with all these, we'll have to think about putting them together for a "Properties of Water" article.
PikeD, 1/14/2014 4:43:42 PM
By late february it is also possible to get thick ice that has been tunneled by running water and the multiple freeze/thaw cycles from the season. This ice may be thick (8"+) but when you drill a hole your auger goes right through. The key to all of the front range situations is to have a spud bar and use it. Three or four hard raps with the bar and that ice is pretty strong.