The state-of-the-art in cave ice coring

Since the first core drilled in a cave ice deposit in 1947, more than 141 m of ice cores has been extracted from 20 cave ice deposits worldwide until 2021. Cave ice drilling projects focused mainly in Central European caves, however, half of the cave ice cores (3 out of 6) published in 2020 represent non-European localities predicts that an increasing number of such projects are focusing on other geographical areas hosting ice caves. Depending on the two types of ice encountered (firnified snow and frozen water), local climatic conditions and cave geometry, cave ice cores have highly variable length (between 1 and 25 m long), time span and continuity of the record covered (from a few years up to several thousands of year). The longest cave ice core in terms of both core length (~25 m) and continuous time span (~10 kyr) comes from Scărișoara Ice Cave (Romania), with several others (in Spain, Slovakia, Austria, Romania, the USA) reaching back in time towards (and beyond) the mid-Holocene. Major challenges in cave ice core science are posed by 1) presence of englacial rocky and woody debris, 2) complex stratigraphy of the ice deposits (often disturbed due to ice flow in a restricted space), 3) problematic chronology and 4) complex mechanisms of climate-proxy information transfer. Regardless, cave ice deposits offered over the past decade several unique records of Holocene climate and environmental change as well as of past microbial and fungal diversity. Because ice caves are located at much lower altitudes and latitudes than polar and mountain glaciers, they face the double threat of both increasing temperatures and precipitation amounts, several possible milennial old deposits being lost over the past few years. An ongoing race to salvage the paleoclimatic information these ice deposits holds is thwarted by climatic, financial and knowledge risks.