COLD-AIR TRAPPING CAVE PASSAGES AND ALGIFIC TALUS SLOPES IN THE CENTRAL APPALACHIANS: SIMILAR THERMAL REGIMES POINT TO SIMILAR BALCH REFRIGERATION MECHANISM

Annual temperature cycles in parts of two southeastern West Virginia caves show similar patterns to algific (cold-air-producing) talus slopes in the Central Appalachian region. These atypical cave passages experience pronounced seasonal variations with mean annual temperatures up to 10° C lower than adjacent landscapes. Maximum temperatures are reached in late summer or early fall, followed by 2 to 3 months of open circulation when cold outside temperatures trigger repeated brief 4° to 8° C declines followed by partial temperature recoveries. Minimum temperatures as low as -15° C have been recorded in early winter. Icicles, ice stalagmites, and other ice forms appear to reach maximum development weeks after the temperature minima, followed by gradually diminishing temperature oscillations as passage temperatures rise toward 0° C by early spring. Temperatures rise gradually through spring and summer, when the cave air system appears relatively closed to short-term outside temperature fluctuations. The similarity of annual thermal cycles suggest these cold cave passages are driven by the same “Balch refrigeration” mechanism that operates on many algific talus slopes. In the Balch (1900) model, density stratification restricts air exchange when outside temperatures are relatively warm, but permits wholesale rapid air exchange whenever outside air is colder than air in the passages. A key morphology for trapping cold air is a wide entrance with downward sloping passages connected to closed or partially closed lower rooms. The cold-air trapping caves explored to date appear to be remnant paleo-passages, overlying but separate from active systems. Crowder Cave data demonstrate side passages connected to cold air traps may behave more typically, with nearly constant annual temperature cycles. It is very likely the cold passages were perennial ice caves throughout much of the Pleistocene. Throughout the Holocene these passages served as refugia sheltering unique biota like the federally endangered Indiana Bat (Myotis sodalis). In the face of climate change and white-nose syndrome, sound management of these karst features must include passage modification management so that modification does not inadvertently disrupt the closed systems required to contain density-stratified air.