SEASONAL TEMPERATURE CYCLES IN CENTRAL APPALACHIAN COLD-AIR TRAPS

Algific talus slopes, rock cities, or artificial “ice mines” support at least seven cold-air traps on Paleozoic sandstone landscapes in West Virginia and Pennsylvania. At least two sites are associated with large late Cenozoic slope failures. Cold-air flow at two natural algific talus slopes supports refugia for boreal flora. Today, these Central Appalachian cold-air traps support ice into May, June or even July. Descriptive accounts from the 19^th and early 20^th centuries indicate ice persisted even later, but quantitative data are insufficient to rigorously establish historical trends.

Three cold-air trap sites have been instrumented with Hobo temperature loggers through at least one annual cycle: Ice Mountain talus slope, WV (6.5 yr), Trough Creek Ice Mine, PA (2.5 yr), and Little Beartown rock city, WV (1 yr). The three temperature records show remarkably similar annual cycles, despite the sites’ diverse origins and geological settings. Maximum temperatures of ca. 10 to 12°C are reached between late August and early October, followed by a 4 to 5 month interval when 4 to 10°C 24-hour declines are followed by partial temperature recoveries. Base temperatures decrease with successive decline-and-recovery cycles, typically falling below 0°C in November or December. Temperatures between -3 and -8°C typify mid-December to mid-March, with brief periods as low as -12 to -20°C triggered by discrete cold weather events. Ice accumulation in the cold-air traps increases dramatically in late winter and early spring. Temperatures stabilize near 0°C for a 2 to 3 month interval after the spring equinox. Warming occurs slowly (<0.1 C°/day) after surface ice disappears, suggesting lingering subsurface ice may moderate summer temperatures.

Temperature and air-flow data at the cold-air traps favor a one-way, density-driven (cold-air-sinks) air-flow model, as proposed for Ice Mountain by Hayden (1843) and widely promoted by Balch (1900) for ice-cave circulation. Appalachian sandstone cold-air traps do not conform to the two-way air-flow model Frest (1981; 1983) proposed for algific talus slopes developed in carbonate landscapes in Iowa.