<p>In this photo provided by the University of Alaska, Sam Dementieff checks a hole in the ice on the Tanana River as Dave Norton looks on and Knut Kielland approaches.</p>
December 12, 2013
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December 12, 2013 8 p.m.
Tanana River study: How to identify dangerous ice
FAIRBANKS, Alaska (AP) - After mushing dogs on the Tanana River for 20 years, both for trapping and recreational purposes, Knut Kielland decided to figure out why the river freezes - or doesn't freeze - the way it does.