Dr. David L. Strayer Freshwater Ecologist Share: January 15, 2012 When my friend Natasja van Gestel was talking about her recent trip to Antarctica, I was surprised to hear her say she didn’t know ice was beautiful. Of course ice is beautiful — it’s one of the most beautiful things we get to see in our daily lives. It’s just that most people only see ice in ice cubes. Looking for the beauty of ice in an ice cube is like looking for the majesty of the sea in a glass of water. Ice is beautiful in its many forms. Probably the most familiar kind of ice (other than the ubiquitous ice cube) is pond ice. (Be careful if you’re planning to go out and look at pond ice after reading this — you can fall through and get miserably cold or even die. I like to have at least 4 inches of good black ice under my feet before venturing out, or know that the water is so shallow that I can walk away if I fall through). “Black ice” contains no air bubbles or snow and forms on clear, cold nights. It isn’t black at all, but so perfectly clear that nothing blocks your view of the inky darkness of the deep water beneath your feet. Walking on thin black ice is both unsettling and enchanting. Because the ice is so clear, it feels as though you’re walking right on the glassy-calm water. This is unsettling because you know it’s impossible, and you expect to wake from this dream and plunge into the cold water at every step. It’s enchanting because you can see right down into the water and look at the plants and fish swimming under your feet (a friend once watched a beaver swim between his feet). When you chip through black ice, it comes up clear and bright, like huge sparkling gems. Not all lake ice is so benign. Late in the season, ice forms long vertical crystals the size and shape of pencils or candles. This “candled” ice easily breaks along the junctions between the crystals, so it has no strength and is very dangerous. I once chopped through 18 inches of candled ice near a creek mouth with just three strokes of an ice spud before retreating gingerly to a safer place. What about streams? I often hear people say moving water can’t freeze, but moving water will freeze like any other water when it hits 32 degrees. Once it gets below 39 degrees, water actually gets lighter as it gets colder. As a lake cools on a still winter night, the coldest water floats on the top, where it gets colder and colder until it freezes. For a lake to freeze on a still night, only that top skim of water needs to cool to the freezing point. The water movement in streams keeps such a skim of cold water from forming, so all the water in the stream needs to cool to 32 degrees before it freezes. When streams do freeze, they present a most unearthly scene. If you go down to a stream the morning after a bitter cold night, you’ll see the water steaming. Long needles of ice crystals (called “frazil ice”) will be forming all through the water. These crystals are sticky, and pile up like frigid pillows on stones and logs in the riffles, instead of forming a solid sheet on the water’s surface. Although you may not think of it as ice, the frost that forms on windows is one of the most beautiful forms of ice. When I was in college, a building on campus had a two-story glassed-in lobby. On the coldest mornings, those panes would be frosted with feathery plumes taller than a man, as if the lobby had been paneled in etched silver plate. You can see smaller versions of such striking scenes on your own windows. I think what surprised Natasja about the ice she saw in Antarctica was that it was bright blue, not white or dull grey like an ice cube. Pure ice is optically very much like unfrozen water, so if you see thick, pure ice (like in a glacier or an iceberg), it will be disconcertingly blue, just like the sea. You may not be lucky enough to see a blue glacier this winter, but you can get out some fine cold day this winter to look at a frozen pond, or a steaming stream filling with frazil ice, or even just the frost on your window. Ice is too beautiful to ignore. Share: Dr. David L. Strayer Freshwater Ecologist Dave Strayer is a freshwater ecologist whose work focuses on measuring the long-term effects of zebra mussels on the Hudson River ecosystem, and understanding the roles of suspension-feeding animals in ecosystems. Strayer also works on broader issues in freshwater conservation ecology and invasion biology.