Response of Alpine cave glaciation to millennial-scale climate variability during the last glacial period

This study examines the response of Alpine cave glaciation to millennial-scale climate variability during the last glacial period, using cryogenic cave carbonates (CCC) as a paleoenvironmental archive. Focusing on the isolated homothermic Hochkogeltunnel gallery in Eisriesenwelt, a large cave in the Austrian Alps, we analyzed coarse-grained CCC (CCC-c) to reconstruct past cave temperatures and ice presence. ²³⁰Th dating reveals nine distinct phases of CCC-c formation over a period of 67 ka (77.9 ± 0.5 to 11.2 ± 0.5 ka BP), with most occurrences aligning with interstadial warming events recorded in Greenland ice cores and Alpine stalagmites. Thermal modeling suggests that rapid temperature increases during interstadials warmed this cave gallery to about −1 to 0 °C—the critical range of CCC formation—within approximately 56 yr–131 yr and remained at this temperature for about half a century. Since the model accounts only for conductive heat transfer, this represents a maximum time estimate, yet remains within the uncertainty of the ²³⁰Th ages. Our findings confirm that karst hydrology and cave microclimate and thus perennial cave ice responded sensitively to glacial-age climate fluctuations, highlighting the value of CCC-c as a high-resolution archive for past subsurface temperature variability.