Waiting for Water

Just before hamburgers were served to son Todd and me at Birch Lake Bar a week ago, co-owner Ed stopped by our table and lamented the lake’s condition.

I’d been enjoying the extended thaw – greatly, I might add – but to Ed the lake’s surface of deep slush meant the end of snowmobile season, the end of ice fishing, and so a tough time for business. I can certainly sympathize: an early thaw means different things to different people.

Now the question of the day is: When will our lakes open up? That depends on how the weather behaves from here on, though the past two weeks of well-above-average temperatures have given the thaw a nice head start.

Last year and the year before, the ice went out here on Birch Lake a few days after the official fishing opener (first Saturday in May). It went out a great deal earlier in 2010, the first year we had our land here – I remember wading in the lake, quite comfortably, in mid-April.

2011 was a different story. On April 16, when our family held a ceremonial groundbreaking for the cabin that has since become our year-round home, the lake was still frozen solid, the day cold, wind-blown snow stinging our faces. We drank our champagne huddled inside the RV trailer that served as our first shelter.

As for 2012, I have written evidence of an early ice-out. An entry elsewhere on this blog says I put the pier in on April 7, the Saturday before Easter. Are we due for another early open-water season? Signs point that way, but we can’t forget what April and May were like last year: Cold, cold, and more cold, with a couple of April blizzards tossed in.

Right now, as I write, on Sunday, March 15, it’s pleasantly mild, about 50 degrees, and the forecast, if it can be trusted, calls for highs well into the 40s for the next several days. The snow has melted off the metal components of our pier, arranged neatly on shore, and off the cedar pier board sections I stacked and covered with a tarp last November.

If you’re like me, you’re aching for the ice to be gone and for the start of whichever open-water recreation you prefer. It’s a wondrous time – the days getting longer, the clock sprung ahead, loons on their way north, the long months of spring, summer and fall awaiting, full of promise. We could do worse than to have an early ice-out bring that promise forth sooner.

Magic on ice

Assuming our cold snap goes away and stays gone, something almost magical will soon happen to your lake’s ice. It’s called candling, and it reveals a property of ice that’s hidden from us most of the time. It’s fascinating, but it also leads to a significant hazard for those venturing out for late-season ice fishing or other adventures.

As the thaw sets in, lake ice changes from what we know as a strong, monolithic structure to a matrix of crystals, arranged (if imagined from above) as hexagons, like the cells in a bee’s honeycomb, though by no means as perfect. These crystals align vertically, from the top of the ice to the bottom; they are shaped somewhat like candles.

In its candled state, ice is often called “rotten.” You can see how weak it is in this video. A man (wearing a life vest, over shallow water) walks on candled ice and repeatedly breaks through, even though the ice is 13.5 inches thick and if intact would support a 9,000-pound vehicle with a 3:1 margin of safety.

How and why does this happen? The best explanation I got came from Dan Heim, an old friend, an Arizona resident, and author of the Sky Lights blog about astronomy, meteorology, and earth science.

As ice forms, he tells me, the mostly hexagonal crystals grow from the surface down. In the dead of winter, the crystals are strongly fused (frozen) together so that the ice appears monolithic.

“Ice expands as it warms, up to the point where it melts,” says Dan. “As the thaw approaches, the ice goes through many cooling and warming cycles, and that’s where the stress to form cracks begins to build. When you look at images of candled ice, you see that most but not all candles are hexagonal. Because of impurities in the water, the fractures are sometimes non-hexagonal. As things warm up, the ice preferentially cracks along the crystal boundaries.

“Once the cracks form, that’s where additional melting happens, further separating the candles. The load-bearing capacity of the ice, which is proportional to the square of its thickness, starts dropping as soon as the microscopic cracks form.” And dropping quite fast, one might add. So for safety’s sake, stay off of candled ice.

Another thing about candled ice: It can be almost musical. If you were to find a thick sheet of such ice driven by wind up onto shore, and if you were to tap at it, candled crystals would tumble off, making a soothing sound a bit like a set of wind chimes. Magical indeed!