Sinkholes formed by crustal subsidence often develop in karst topography where the ground is underlain by limestone. Sinkholes form enclosed basins in a range of sizes, often with no natural outlets. Large diurnal air temperature oscillations occur on the floors of some sinkholes, producing low nighttime temperature minima and strong nighttime temperature inversions. Sinkholes in a range of sizes provide a natural laboratory for the investigation of physical processes that lead to the growth, maintenance and dissipation of temperature inversions.

This talk investigates temperature inversions that formed in four instrumented sinkholes in the eastern Alps at an altitude of about 1300 m MSL during the fall and winter of 2001-2002. The largest sinkhole investigated, the Gruenloch sinkhole, has been previously identified as one of the coldest spots in central Europe, with temperature minima reaching as low as -57°C. The talk will focus on the dependence of low minimum temperatures and strong temperature inversion structures on synoptic weather influences, snow cover presence, and terrain characteristics including sinkhole depth, diameter and drainage area. Several case studies from the winter of 2001-2002 will be selected to illustrate temperature inversion development in the sinkholes using data collected continuously from three weather stations and 58 temperature data loggers located within and above the sinkholes.