Mushroom ice opposed soldiers in British Columbia and Yukon. In Alaska mushroom ice defeated them. During the winter of 1942/43 commanders positioned regiments along the length of the brand new, rough draft of an Alaska Highway to keep it open for truck convoys from Dawson Creek to Fairbanks.
Against daunting odds, soldiers succeeded in British Columbia and Yukon. Truck convoys rolled as far as Whitehorse. But only a very few vehicles, and certainly no truck convoys made it on to Fairbanks.
The Tanana Valley in Alaska served up especially bitter and sustained cold. A website named “Northern Alaska Weather and Climate” explains. “The Upper Tanana Valley… gets very cold; it is about 1000 feet higher elevation than the Yukon Flats…” And the Valley occasionally suffers winds as high as 80 miles per hour which can drop the wind chill to 80 or even 100 degrees below zero. That weather the took the job of keeping the winter road open from daunting to impossible.
The road through the Tanana Valley crossed rivers and stream after stream; and, in late summer and fall, the soldiers had installed culverts so water could flow under the road or had bridged rivers and streams with rough timber bridges. The bitter cold of winter ruined everything.
Even bitter cold couldn’t form ice in a swift moving current. The water continued to flow. But ice formed along the sides and the bottom of the flow, gradually compressing its channel, raising the water level until water flowed over a culvert, over and around a bridge. Great mounds of ice formed and grew to block passage. Because the continuously growing and expanding mounds of ice seemingly mushroomed out of nothing, the soldiers called them “mushroom ice”.
Through Alaska snow and mushroom ice blocked the road at every turn.