All about ice

Very few of life’s sensations are quite as sickening as the feeling of ice going out from under you. Whether you’re afoot, on a snowmobile, or in a vehicle, the experience is both terrifying and life threatening. 

Fortunately, with the proper precautions and a healthy dose of respect for the magic carpet that transports us to and from the fishing grounds, hardwater adventures need not be unduly hazardous.

A lifetime in the Ice Belt has provided me with several frigid dunkings and more than one close call. The closest occurred during a midwinter outing three decades ago, when a friend and I foolishly tried to drive my late-1970s model Mercury Capri – arguably one of Detroit’s gamest dinosaurs – through a narrow channel linking two lakes.

To make a long story short, we partially broke through while thundering out of the channel at over 50 mph. Thanks to a combination of momentum and the collective efforts of our guardian angels, we skipped to safety without plunging under the icepack.

Ice life histories

In hindsight, a number of contributing factors were in play that day. 

First of all, we hadn’t checked the ice conditions ahead of us. And there was current in the channel, which limits ice formation and weakens what ice does form over it. Finally, at midwinter, the ice had experienced a series of thaws that greatly reduced its strength-to-thickness ratio.

Our experience highlights the need to understand the factors affecting ice thickness and strength – ice life history, if you will. 

Let’s start at first ice, which often occurs when frigid air and water convene on a calm early winter night. The resulting sheet of clear, fresh ice is strong for its size – 4 inches of newly formed ice may support a person on foot, while a foot or more of aging, partially thawed ice may not.

Under ideal conditions, cold, dry weather fosters the fledgling icepack, speeding the formation of a foot to 24 inches of clear, solid ice. To be sure, lakes rarely freeze in a uniform manner. Mitigating factors, including flowing water, schools of fish, heat generated from objects in the water, and other considerations, can cause weak spots. Indeed, in some current-swept large lakes, it’s not uncommon to find wild fluctuations in ice thickness. You may have 2 feet of ice in one spot, and 2 inches just a few feet away.

Snow slows the freezing process, and if enough of it falls early on, it can really put the ice season on hold. In December 2013, for example, more than 24 inches of snow blanketed less than 6 inches of ice across the northern Midwest. Because of the snow’s insulating effect, it brought ice formation to a grinding halt. To make matters worse, the weight of the snow pushed the ice below water level, creating a hazardous combination of thin ice covered by slush, capped by a thin skin of surface ice. Only after extended periods of record cold so severe they made locals pray for global warming did the slush start to solidify.

Ice color can also clue you in on its condition. Clear or bluish ice is generally the strongest, while a whitish or opaque appearance indicates the sheet includes water-saturated snow, which isn’t quite as strong due to air pockets. A sickly gray or blackening icepack is common late in the winter, and bears extreme respect. Likewise, honeycombed or slushy textures are red flags that ice-out is close at hand. 

When dirt, bits of vegetation, or brown colorations from plant tannins join the party, it’s really time to pack away the ice gear.

Cracks are a factor all winter, and they aren’t necessarily a bad sign. Dry fractures generally don’t penetrate the ice sheet, and aren’t cause for alarm. In fact, since they often occur when the upper crust expands due to building ice below, they’re actually good signs. 

Water seeping from a crack is another story, however, and you can generally multiply the weight of your gear and vehicle by 2.5 to gauge how much ice is needed to support the load. When traversing any crack, it’s best to cross as close to perpendicular as possible, because paralleling fissures is risky business.

Other general rules of ice safety include being wary on rivers and other flowing-water systems. Not just for weak spots from current – especially in bends, riffles, and funnels – but for the threat of falling water levels. Ice needs water beneath it for support, and if a river drops during winter, walking on the ice left hanging is nothing short of suicidal. In short, if the ice sounds hollow or slopes downward from the shoreline, stay off.

Throughout the winter, ice is subjected to air-temperature changes. In general, when the mercury stays above freezing, bare ice in particular begins to lose strength. 

The U.S. Army Corps of Engineers advises caution following a 24-hour heat wave, while Ohio State University experts say even six hours of thawing in a 24-hour period call for multiplying load weight by 1.3 to determine the necessary ice thickness. On the flip side, the Army also warns that a fast, precipitous drop in air temperature causes ice to become brittle, and recommends staying off the ice for 24 hours.

Bottom line? Never blindly trust any ice. Check with local bait shops, resorts, or guides before heading out onto the ice, and when venturing off established roadways, frequently test the ice with a chisel or auger. Doing so may not only spare you a scary dip in the lake, it also could save your life.

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