Ice harmonics and safety

Paul Smith
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Winter is chugging along and we are plummeting swiftly towards springtime - although last week we had the coldest winter day in three years, the daytime mercury creeped only to a chilling -11 C.

That's here at home in Spaniard's Bay I'm talking about. Off the Avalon, double digit negative temperatures are commonplace.

In Labrador, -11 C would be considered a mild winter's day. People would be strolling about town with spring clothes on. All things are relative, I suppose.

That cold snap did solidify the ponds again and anglers are once again drowning worms, hoping to take home a few plump, tasty brook trout. The wood cutters are venturing over the ice cover to secure fuel for next winter.

My buddy reneged on a trip to the cabin yesterday to haul a trip or two of firewood over Spider Pond. I told him to be very careful, and the same advice goes to anyone else either driving or walking over frozen water. The last thing we want is any more ice-related fatalities this winter.

You need plenty of ice to drive quads or ride snowmobiles over frozen lakes. The Canadian Red Cross recommends 15 cm for walking or skating, 20 cm for parties or games, and 25 cm for snowmobiles.

But we all know that many Newfoundlanders take chances significantly short of these guidelines. Often, the results are tragic.

Complex calculation

The question of ice cover being deemed safe is much more complex than can be categorized by thickness alone. The Red Cross points this out on its website and cites numbers only as a general guideline, or minimum standard.

The problem is that we might measure the ice thickness at one location in a lake and get a full 30 cm of solid ice. Unbeknownst to us, somewhere else on the same body of water there might be a mere 5 cm separating you from an icy bath, or much worse.

Mitigating factors include currents, tides, water salinity, fluctuations in depth, and rocks or logs absorbing heat from the sun. All these can have a significant effect on ice thickness. We all have seen how ponds remain open around the mouths of brooks even through cold winters.

What's most dangerous is when, after very frosty, still nights, these areas do freeze over. The ice might look safe, but in reality the cover is very thin.

So, if a snowmobiler who doesn't know the area happens by, he or she might easily find themselves in the drink.

The irony is that you must be even more cautious after very cold snaps when these sorts of areas lay in wait like booby traps. You must know where the brooks are in all the ponds you ride or walk on. If you venture into virgin territory, be extremely cautious, and make use of Google Earth or topographic maps. Best of all, travel with a friend or guide who knows the area.

The more peculiar factor that many are unaware of is the effect of moving vehicles on ice cover. Some physics is in order. A snowmobile or ATV excites shock waves that travel through the ice both in front and behind the moving vehicle. This can sometimes fracture ice that would otherwise safely support a static load. There's plenty of research data available on this subject due to the winter ice roads that are used to transport goods to isolated communities in the far north.

Speed matters

Many think that driving fast over ice is the safest practice. Not so. Going slow would be a safer option.

Actually, there is an absolute worst speed to drive, but it's all but impossible to predict without a bunch of engineers constantly monitoring the situation. That's what they do in the ice road trucking business, but recreationalists don't have that option.

What happens is that the ice sheet resonates at a certain natural frequency that depends on a bunch of factors such as thickness, density, water depth and so on.

It's kind of like when your car shakes violently due to wheel imbalance or a bump on a tire. It's also akin to how great opera singers can smash wine glasses with only a song.

The bottom line is that you have no idea what the critical speed is, so make sure the ice is plenty thick for moving loads.

That's why the standard is 25 cm for snowmobiling, when we all know that a standing person will break through snow or ice before a stationary snow machine.

Also, avoid driving directly towards shorelines, better to approach at an angle. That's because the ice waves can reflect back upon themselves from the shoreline, creating even more stress in the ice - something like harmonics on your six-string.

We all take note of the ice-related tragedies that make the evening news. They are typically either occurrences ending in death or a heroic rescue of some sort. There are many more incidents that go unreported.

Survived incident

Early this winter, two snowmobilers went though the ice here in the Conception Bay area. Luckily there were no injuries and no report appeared in the media. Both men ended up in the water with their machines sunk to the bottom. One guy had a floater suit on and managed to get back up on solid ice. He then plucked his buddy from the water without incident. Both of them were experienced woodsman and managed not to die of hypothermia before help arrived. They even managed to salvage their snowmobiles from the bottom the next day. But we all know that accidents like this one can end very differently.

Be careful out there.

Paul Smith, a native of Spaniard's Bay, fishes and wanders the outdoors at every opportunity. He can be contacted at


Organizations: Red Cross

Geographic location: Labrador, Conception Bay

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