Radiocarbon dating of fossil bats from Dobšina Ice Cave (Slovakia) and potential palaeoclimatic implications

Abstract

Although Dobšina Ice Cave (DIC, Carpathians, Slovakia) is located outside the high-mountain area, it hosts one of the most extensive blocks of perennial subterranean ice, the volume of which is estimated at more than 110,000 m³. Frozen bat remains were found in the lowermost part of the perennial ice block. They belong to Myotis blythii (Tomes) and the M. mystacinus morpho-group. The radiocarbon dating of bat soft tissues yielded ages of 1266–1074 cal. yr BP and 1173–969 cal. yr BP. The undetermined bat, found in the same part of the ice section in 2002, was previously dated at 1178–988 cal. yr BP (Clausen et al., 2007). The dates testify that the ice crystallized at the turn of the Dark Ages Cold Period and the Medieval Warm Period. The calculated accumulation rate of cave ice varies between 0.7 cm/year and 1.4 cm/year at that time, and is similar to the present ice accumulation rate in DIC. Constant crystallization of ice during the Medieval Warm Period is hypothesized to reflect dry summer seasons since the supply of relatively warm water in the summer is one of the key factors causing the erosion of cave ice. The uppermost sample was covered with 20.6 m of ice. Between ca 1065 cal. yr BP and the present day, the ice grew faster than between ca 1210 yr BP and ca 1065 yr BP by a factor of 1.3–1.8. This may have resulted from conditions favourable for ice accumulation during the Little Ice Age.