Detection of Ice Wedge Cracking in Permafrost Using Miniature Accelerometers. Issue 4 (19th April 2018) - O'Neill, H. Brendan
Abstract: Determining the exact timing of ice wedge cracking in permafrost is challenging. Five miniature accelerometers were installed near the ground surface in the trough of a primary ice wedge within a network of low‐centered polygons in Adventdalen, Svalbard, to test whether these instruments could be used to detect dynamics of thermal contraction cracking. Data from 2003 to 2013 were analyzed to characterize cryoseismic signals in the ice wedge trough. High‐magnitude accelerations (from 5 g to at least 100 g) were typically registered in late winter, when the top of permafrost had cooled to about −10°C; these likely correspond to ice wedge cracking in permafrost. Tensile stresses calculated from temperatures measured in the ice wedge trough are near laboratory strengths reported for ice and mineral active layer sediments, supporting the interpretation that large accelerations are caused by thermal contraction cracking. Lower magnitude accelerations occurred throughout the freezing season, usually coinciding with rapid cooling at the ground surface. These small accelerations may be associated with (i) the initiation of small cracks in the active layer of the trough or (ii) the horizontal and vertical propagation of existing ice wedge cracks. The results of this investigation indicate that miniature accelerometers are an effective, inexpensive, and simple method to determine the timing of ice wedge cracking and rates of crack propagation along ice wedge troughs. Key Points: Miniature accelerometers were tested to determine whether they could detect ice wedge cracking in permafrost High‐magnitude accelerations were associated with low temperatures at the top of permafrost in late winter and indicate ice wedge cracking Lower magnitude accelerations may be caused by small cracks in the upper active layer or crack development along the trough