The Lake Where You Live

Several times here I’ve written about my favorite website that deals with lake ice (http://lakeice.squarespace.com/properties/). I looked it up again recently as I observed the Birch Lake ice steadily thickening.

It was fully one foot thick two Saturdays ago when neighbor Charles and I caught seven species of fish in about two hours (the diversity and energy of life in a frozen lake continues to amaze me). After the recent spell of subzero days and nights I would imagine the ice has surpassed 18 inches and is closing in on two feet.

So the time was right to visit Lake Ice online and learn more about the wondrous phase of water that encases our lakes for the better part of five months each year. Here are some terms from what is essentially a winter lake glossary. 

Density. At the freezing point, ice has a density of 0.916 grams per cubic centimeter. The density of liquid water at the same temperature is just below 1 gram per cubic centimeter. Ice is roughly 10 percent less dense than water; that is why it floats.

Stiffness modulus. This measures the inherent stiffness of a material. Ice has about the same stiffness as hardwood bent along the grain, and about three times the stiffness of typical hard plastics. (Saltwater ice is a significantly less stiff.)

Heat of melting: This is kind of a meaningless term at this time of year. It takes 80 calories to turn a gram of ice into water. The reverse is also true — a gram of water at the freezing temperature has to give up 80 calories of energy before becoming ice. 

Fracture toughness. This measures how easily a crack propagates through a material. Ice has a fracture toughness about one-tenth that of window glass.

Sublimation. Water evaporates mostly from the liquid phases; this term defines the process of evaporation directly from ice to water vapor. The rounding off of deer or animal tracks in snow atop the ice is the result of sublimation.

Refractive index. This refers to how much light slows down when it enters a material like ice or water. The speed of light in ice is about 75 percent of its speed in a vacuum. The index of refraction is 1.309, versus 1.33 for water and 1.52 for glass. 

Quasi-liquid surface. Scientists now believe the water molecules near the ice surface “are sort of attached and sort of loose when it is near its melting point. This is what is believed to make ice slippery.” Ice becomes more slippery as its temperature increases.

Super cooling. Under some conditions, liquid water can cool to below the freezing temperature. For example, this happens when a lake is on the point of freezing, but the surface is being stirred up by wind. The constant agitation continuously fractures the tiny ice crystals that try to form.

The Lake Ice is a great place to visit by way of a laptop computer or phone while having a morning coffee beside a fireplace. Knowing more about the ice can help enhance our appreciation for and enjoyment of it.

Ted Rulseh resides on Birch Lake in Harshaw and is an advocate for lake protection and improvement. His Lakeland Times and Northwoods River News columns are the basis for a book, “A Lakeside Companion,” published by The University of Wisconsin Press. Ted may be reached at [email protected].