With the warm weather of recent weeks, the spring ice season has begun. The Lifesaving Society warns Albertans to beware of spring ice conditions, as spring ice is rotten ice.
Once ice starts to rot, the thickness of ice cannot be used to determine if the ice is safe. Spring ice can be deceptive, the ice may look solid – but beware. “Most Albertans are aware of the risks of thin ice. Unfortunately, very few are aware of the risks of rotten ice”, says Barbara Kusyanto, Chief Administrative Officer with the Lifesaving Society. “Because of the way ice melts, the ice dramatically weakens even as it retains much of its original thickness.”
In spring, a 40 cm thick sheet of ice, which could once support a truck, may crumble under the weight of a child. When water freezes, minerals in the water make vertical veins in the ice. These veins melt faster than the rest of the ice (called candling), causing vertical channels and the ice to weaken along those channels. This ice may collapse suddenly and without warning.
Other factors affecting spring ice safety:
* Beware; ice can erode from the bottom up, with no obvious warning signs on top.
* Melting upstream can create run-off that weakens river ice.
* Ice near shore will melt more quickly.
* Saline water run-off from roads and melting snow dumps can create “hot spots” that weaken the ice.
* Tree stumps, rocks and docks absorb heat from the sun, causing ice around them to melt.