Nature of Lake Ice

20110108-EndlessSkate-SouthBay-ChandosLake

Game On!

First off, the book “Peterborough and the Kawarthas” by Peter Adams and Colin Taylor (Trent University) addresses the subject of the lakes in winter very well (Chapter 6). The following section on the nature of ice and snow cover draws from this reference.  Peter Adams has graciously allowed the use of his fig 6.7 below.

The ice and snow cover consists of three components: Black Ice, White Ice, and Snow.

The Black Ice is the first ice to form and from then on, forms from the bottom at the ice-water interface. It appears black because it is translucent, and light passes through without being reflected back.

Snow, of course, is the natural frozen precipitation that forms the top cover.

White Ice is the sandwich layer. As the snow accumulates, the weight forces the snow/ice cover down, and water from the lake comes up through the holes and cracks, and floods the surface and mixes with the snow. This then freezes and forms “white ice”, which is opaque, and reflects all light. If any of the snow melts and refreezes, it is also part of this white ice component.

As the snow/white ice cover continues to grow, it insulates the black ice, thus slowing or ceasing its formation.

So there is a pattern of growth and decay of these various components.

The following figure from Adam’s and Taylor’s book captures this very well. (used with permission from Peter Adams)

snow ice cover fig 6 adams

Candling of ice is a state that the ice might go through as it thaws.  It is fairly dangerous, because even though the ice is “thick”, it has no strength.  If you have an interest in ice, have a look at the Swedish site: Lake Ice  This is by far the best site I have found regarding ice science, ice safety, and practical information.

ice thickness

There is a difference between “Break Through” ice thickness, and “Getting Back On” thickness.  if you are on skis or gliding on 2 skates, and break through, the ice likely isn’t strong enough to let you crawl back onto it.  Another big concern is that the ice is not uniform, in thickness or in strength..

So, on Chandos, for my money, you had better see no open water, and a thickness of 5 inches before venturing out.