Boundary Waters Quetico Forum :: Winter Camping and Activities :: Thin Spots on the Ice
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marsonite |
quote NotLight: " An important point to keep in mind is that the water at the bottom of a frozen lake is 39 degrees F. So anything that causes that water to come to the surface will result in thin or even no ice. This could be a shallow pinch point an a lake with a lot of water moving through it or the outlet of the lake. It's the upwelling of this "warm" water that thins the ice, not the movement of the water necessarily. |
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OldFingers57 |
Wind is another factor in ice formation, if it is windy ice will not form due to the movement of the water. Also waterfowl can keep areas of water open due to there using it. Thus a lake can have a section that is thinner then other sections due to waterfowl keeping it open and the rest of the lake ice is freezing up thicker and then the waterfowl leave the open area and it freezes up but is thinner then the rest of the lake ice. |
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OldFingers57 |
quote marsonite: "Actually in a lot of spots it's the upwelling of the warmer water from the lake's depth that thins the ice not the current. I used to darkhouse spear pike on Winnie at plughat point, the bay before the outflow of the lake. There was zero detectable current but still the ice in that bay would be 4 or 5 inches thick while the main lake basin was several feet thick. So how do you know it was actually the temperature of the water? Or are you deducing that since you saw no current that it has to be the temperature of the water? |
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wingnut |
The Arctic Armor ice fishing suit is another great piece of safety gear because if you break through, you float. |
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marsonite |
Obviously moving water doesn't freeze as well, but again, it isn't always just the movement. |
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marsonite |
Likewise, I grew up near lake Vermilion and quite a few people have broken through the ice in areas that don't even seem to be in narrows but are shallow. Same effect. Slight currents bringing that warm water up. I guess my point is that you really have to be careful, especially on shield lakes with irregular bottom contours. And don't go anywhere near a major outflow. Mind you, I agree totally with the general advice you gave. Moving water is bad news. |
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OldFingers57 |
quote NotLight: " Yes that happens quite frequently where you will keep breaking thru till you hit some ice that is strong enough to support your weight. It can be very tiring even in an ice rescue suit. The best thing to do is go back the way you came and fell in from. As you know that ice is strong enough to support your weight till you hit the thin spot. Another thing I tell my Ice Rescuer students to do is to take the broken pieces and shove them under the ice that may be thin as it will help support more of their weight. Also when using Ice picks/awls. Don't try driving them into to the ice too hard as you can actually crack the ice by doing so. You want to set them somewhat and have them at an angle away from yourself. Plus don't go out an arms reach, do small increments so you are using your bicep muscles to pull you out more. Plus get your legs out behind you and do either a frog kick or a flutter kick to help push you up onto the ice. |
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2old4U |
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egknuti |
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nofish |
There are so many reasons why thin spots form or why areas never freeze as solid as surrounding areas. Many of them have been covered and both marsonite and OldFingers are correct. Moving water can weaken ice or prevent it from forming and also warm water coming up for the lake bottom can weaken ice (although if warm water is coming up for the bottom that also suggests at least a small amount of moving water for that to happen so both effects are at play there). If you are unfamiliar with a body of water there are a few things you can do to increase safety. 1. Use a spud bar and check the ice in front of you as you walk. If the spud doesn't go through then neither will you. I've had a spud bar save my life more than once. This may not be super easy if on skis since you've already got poles in your hands and doing a scouting trip ahead of you is very tedious and time consuming and takes a lot of extra energy. 2. Do your homework. Ask around about known bad ice spots before heading out. Often times poor ice forms in the same area year after year and is often known to locals. That doesn't mean new spots don't form but at least you have info about known spots. Also study maps so identify pinch points, outlets, inlets, etc. When you approach these areas tread carefully. 3. Carry a set of ice picks around your neck to aid in climbing out of the water if you do go in. Ski poles can also work, just hold them down at the base and use the pointed end to dig into the ice. 4. Don't travel alone. Sure helps having a safety buddy. |
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NotLight |
Thanks nofish. I wonder if ice picks give one a false sense of security. Still a good idea, but, when I went through some thin ice near shore last year (not a big deal), it was a reasonably big area of thin ice. Kind of hard to pull yourself out, without just breaking through the ice again as you pull yourself up/our of the water. Eventually maybe you get out, but you'll be pretty cold by then maybe. So yeah, best not to be alone if possible, I suppose. I will look for some ice rescue videos on the web. Maybe lose some weight :( |
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NotLight |
I'm pretty comfortable skiing on the lake by my house (after christmas), because there's enough snowmobile and car traffic to "test it out for me". But how do you guage where there might be thin ice on a winter BWCA trip. Also, if you have slush, how do you distinguish between that and thin ice? When I went last year, there was thin ice and open water even in mid-January almost anywhere there was moving water. But couldn't it be anywhere as a result of a spring, or a subtle pinch point on a lake that is really part of a river system? That's what I kind of assume - I could fall through the ice just about anywhere. |
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OldFingers57 |
Thin ice can be a result of many different things from springs, currents, waterfowl, to obstructions in the water and other bodies of water flowing into a body of water. As for how to know if the ice is strong enough you could "sound" the ice using a large wood dowel/closet rod. Although this can be difficult with snow on the ice. Snow masks the ice and doesn't allow you to see the color of the ice. If there is no snow on the ice you want to look for clear or black ice. Milky ice or ice that is slushy or is kind of honey combed is not strong. |
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Canoearoo |
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OldFingers57 |
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ZaraSp00k |
I try to stay near shore, it is also usually less windy there and you see more wildlife. There have been a couple times I have been in danger of falling thru when by myself, makes you smarter for the next time. Caution and common sense are your best pieces of equipment. |