For the past two years, a mysterious hole has appeared in the same location on Lake Spofford’s ice. This phenomenon is new in the lake’s history. Its cause has become quite a riddle, and its appearance this year created a problem for establishing the “Ice In” date for the Spofford Lake Association (SLA) first annual Ice Out Lottery. After consulting with the State Environmental Service Department, the Ice In date was finally declared as January 12th, because ice covered the entire lake on that day, except for the infamous open ice hole.
Even without a definitive Ice In date, the Ice Out Lottery has already sold a hundred plus tickets. This means the winner will take home at least $500, with the balance being evenly distributed between the SLA and the Chesterfield Historical Society. To see all the details and purchase a $10.00 ticket, visit the Ice Out Lottery Page on the SLA website. Enter as many times as you would like.
A lake begins to ice over when the chilled water molecules at the surface spread apart and the surface water becomes less dense than the water below. This expansion allows the cooler surface water to float upon the slightly less dense warmer water below. Once the surface water cools to about 32⁰, the water molecules crystallize into interlocking lattice-like patterns and ice is formed. Once ice starts to form, the lake surface and the air above it continues to be colder than the water below, thickening the ice. (This paragraph was not in the original e-mail)
But why is the hole not freezing over? To keep an open area in the ice, the warmer water below must be reaching the surface. There are several possible reasons for this: turbulent currents, decomposition bubbles from decaying organic matter driving warmer water to the surface, or an increase in groundwater flow forcing the warmer bottom water upward.
Lake Spofford is predominantly spring fed. Springs occur when water pressure causes the natural flow of groundwater from an aquifer onto the earth's surface. In this case, the water gathers in a bowl-shaped basin creating Lake Spofford. The origins of Lake Spofford's major springs are unknown. However, if conditions change, their water flow may stop, increase, or decrease, sometimes dramatically.
Also, as Spofford’s shoreline has developed, the lake bottom has changed from predominately sand to organic silt. Because the lake has a low outflow, the material is not being flushed out. This additional sedimentation could affect the feeding springs’ locations and flows. Also, as organic material decays, it takes oxygen out of the water, increases the CO2, and alters the chemical make-up of the lake’s bottom. In large enough quantities, these chemical conversions may affect the overall dynamics of a water body.
Whether it is a change in the feeder springs flow or location, major alterations in the bottom's makeup, lack of outflow to clear away sedimentation, a combination of factors, or some yet unknown reason, the SLA is trying to solve the Lake Spofford Ice Hole Riddle. Its location has been triangulated so that the area can be investigated once the lake warms up.
In the meantime, please be careful on any lake ice. According to the New Hampshire Fish and Game guidelines, there should be a minimum of 6” of hard ice to support individual foot travel, 8”-10” of hard ice for snowmobiles or ATVs. For further information see NHFG's free on-line brochure, Stay Safe on the Ice.