Spring Ice Safety Considerations


by Bob Dill - March 1990

The spring is often the best part of the sailing season. The days are longer, the weather is warmer and the snow is off the ice. All of this also changes the character of the ice and brings new hazards to watch out for. Many of the scarier weak ice stories I have heard are associated with advanced thaw conditions.

This time of the year we sometimes sail on ice well thawed but has a refrozen surface from a cold previous night. The large areas of an ice sheet can become dangerous very fast because the strong sun thaws the ice much more quickly than it would in December.

How likely this is to happened depends on several factors including:

  • How thick the ice is.
  • How Much internal melting has taken place in the thick ice.
  • The thickness of the reformed surface.
  • The temperature, wind and sun strength.
  • The type of ice involved. (See article on Ice Grain Structure)

Deciding how safe an ice sheet will be later in the day under thaw conditions requires a solid base of experience and the weather history. As always in our sport, careful observation and prudent judgment is the basis of safe iceboating.

Two important aspects of the ice condition are the ice thickness and looking at the consistency and structure of the ice through its thickness. Several inches of snow ice over a couple inches of water ice is a bad bet for a 50 degree sunny day. The same can be said for 10 inches of well honeycombed ice with an inch of hard ice on top from a cool night.

A sharp fisherman's drill is a good way to assess the ice thickness and condition. You can tell, with some practice, a lot about the underlying ice by the way the drill goes through it. Drill part way through and pull the drill out. If the ice thawed enough to melt out the grain boundaries, water will seep into the hole. you can tell how thick the refrozen surface layer is this way. You can also poke partially drilled holes with a probe to determine the ice type.

Other things to consider are:

  • Pressure ridges deteriorate into wide stretches of water.
  • Gas holes reappear.
  • Contraction cracks erode into runner eating holes.
  • The ice over shallow areas will melt first.
  • Lake levels rise, further deteriorating conditions around the shore.

Rescues on well thawed ice can be very difficult. There are times the only reasonable way is with a hover craft or helicopter. This is a good time of the year to carry throw ropes, to wear wet suits and be extra sure you have your ice claws (bear claws) with you. A long rescue rope combined with cold water protection (immersion suit, dry suit or a wet suit in decreasing order of preference) should be used by anybody considering an across the ice rescue. Having a well thought out and tested rescue plan will is important.

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