Rates of Periglacial Activity Along an Elevational Gradient, White Mountains, California

Periglacial research has been conducted in the alpine zone of the White Mountains since 1991 and has been integrated with the international Global Observation Research Initiative in Alpine Environments (GLORIA) project since 2005. Study sites range from 3200 m at the southern end of the research area to 4250 m near the summit of White Mountain Peak. This elevation range includes measurements on a variety of lithologies and across several micro-climates. Wooden dowels are used to measure annual vertical movement and surface markers are used to measure horizontal movement. Dowels and markers are placed in grid patterns in a variety of active small-scale sorted circles (frost boils) that often lie within large-scale relict sorted polygons. Rates of vertical movement have decreased since measurements began with an average of 16.8 cm in 1991-1992 decreasing to an average of 10.6 cm between 2005-2009. Surface markers are more consistent with an average of between 31 to 56% of markers being overturned depending upon site location. Temperature (frequency of freeze-thaw cycles) and available water are the driving mechanisms for the surface movement with wet years showing greater rates of activity than dry years. Climate change has significantly decreased activity in the lower elevations, while high elevation sites near the summit remain highly active.