After the chill, is it safe to step out on the ice?
After a mild start, the winter finally produced a stretch of snowy and bitterly cold days. Safe to strap on the skates and venture out onto Swedish waterways? A cross-country skater gives a primer for ice safety.
If you want to know when a local lake or stream has frozen enough to support your weight, you need to follow the weather, said Thure Björck a member of the Stockholm Skate Sailing Club who sits on its safety committee.
"We have a climate where it's cold some days, and then it's not cold. So you always have to follow the weather forecasts to actually be able to see when it's time for different lakes to have enough ice and a good surface without too much snow," said Björck.
A simple rule of thumb, according to Björck, is that for the shallow lakes you might find in the Stockholm region you would need at least two cold and clear-weather nights before you would consider venturing out on the ice. For larger and deeper lakes, it depends. Parts of a body of water might be safe to walk or skate on, and other parts might not be frozen at all.
Snowfall complicates things. First, it's not as easy to see the border between thin and thick ice. Also, snow can act like an insulator meaning the ice underneath thickens more slowly.
"We don't like the snow," said Björck. "We like the black ice because it's easier to skate on and it's also much easier to see if the ice is thick enough for us."
Five centimeters thickness is the rule of thumb, but Björck says that also depends on when in the season one ventures out. Five centimeters may suffice during the first freezing days of a cold season, but later in the winter there are more variables. The ice may have melted and refrozen, which affects its integrity. Or it might have layers of compacted snow which forms a more porous ice than frozen water. Five centimeters works as a general rule for "black ice," said Björck, the frozen water uncovered by snow.
To test the ice cross-country skiers carry "testing poles," which resemble ski poles. They poke the sharp point of the pole down into the ice to see if it breaks and to note its sound. Thick ice makes a lower thud, and thinner ice makes a higher-pitched crack.
In the end it comes down to experience and knowing your body of water. Björck said he has been cross-country skating for nearly five decades. Variously called "nordic skating," "trip skating," and "tour skating," the sport features a longer sort of skate blade, frequently attached to a regular boot, which is preferable for multi-kilometer trips over lakes, rivers, and even the Baltic Sea.
Because they travel long distances, cross-country skaters do not know in advance how thick the ice is. So they need to be able to evaluate the ice on the spot. And they prepare for the worst.
To be safe skaters regularly carry a number of safety items in backpacks in case they break through into the cold water: a flotation device to keep their head above water, "ice claws" which are handheld spikes used to smack into the nearest icy surface to pull oneself out of the water, a safety rope that can be thrown to a fellow skater, and a knotted plastic bag that keeps a set of clothes dry.
There are few bad accidents with skaters, says Björck, because they have know-how about the ice and because they bring safety equipment. Still an avid skater, Björck said that he has fallen through the ice dozens of times. How does it feel? Shameful, he said.
Ice Safety Tips
1. Don't go alone
2. Wear a helmet especially if you are skating.
3. Listen to the ice. Higher pitched sounds means the ice is getting thinner.
4. Bring equipment for if you fall in: ice claws, a safety rope, a flotation device, a knotted plastic bag with dry clothes.