Streams of Warm Ground Water Under the Ice


Shelburne Pond is one of our most popular skating ponds.  About 20 years ago I found a peculiar narrow (2 feet wide) finger of thin ice that stuck about 100 feet out into Shelburne Pond in Vermont.  I have looked for this ever since withouit success.   This year we found six of them. 

Summary:

The bands appear to be related to groundwater flow from shore, perhaps injuected under the ice as a shore based spring.  Their occurance appears to be related to a warm January with little frost in the ground.  The following appear to be factors in their occurance.

 

  • Warm conditions (little frost in the ground to inhibit ground water flow).  This can be either early in the season or mid-winter warm spells or at the end of the ice season.
  • Rocky ledges next to the ice (or nearby) and rock that has ground water passages.  Rock layers that dip toward the ice sheet.  Also swamps that have ground water moving through them can create underice streams.
  • They are wider at the shore and extend up to 100 feet from shore, nearly perpendicular to the shore. 
  • They are likely to occur at the same places when the conditions are right.

 

There is well over a mile of rocky and swampy shoreline around Shelburne Pond.  We only found thin ice from these streams in four places, three of them within 1/8 mile of each other.  

Details:

 I got the following from Doug, a friend,  on January 29, 2017