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Microclimate and ice deposits research in Crna ledenica ice cave (Biokovo Nature Park, Croatia) 2016–2019

Crna ledenica ice cave is located at the northern slope of the highest Biokovo Mt. ridge. This area is in the central part of the Biokovo Nature Park in the Dalmatia region (southern Croatia). Biokovo Mt. (1762 m a.s.l.) is known for numerous karst phenomena, especially large and deep dolines and shafts. Apart from being a relief barrier between the Adriatic coast and continental inland of Dalmatia, Biokovo Mt. is a strict climate boundary that is also important for local cave climate and hydrological properties. Some of the shafts in this high mountain area contain perennial ice and snow deposits. In the past, the ice was extracted and transported to the coast and hinterland for conserving food and other purposes. Crna ledenica (Black ice cave) has four entrances at elevations 1479–1503 m a.s.l. connected with one vertical passage and a large hall. The hall dimensions are 58 x 28 m with a maximum height of 33 m. The cave was developed in tectonically highly disturbed and well karstified Cretaceous limestone beds. After initial karst corrosion, important processes in cave formation were collapsing and enlargement driven by cryofraction. Although it was known to the local population for a long time and explored by cavers for many years, the cave was surveyed for the first time by the cavers of the Croatian Biospeleological Society in 2004. In 2016 it became a microclimate observation point in the frame of cavers research project supported by the Department of Geography (UniZG), Speleological section HPD Imber (Omiš) and Caving Club Samobor. The microclimate is monitored by data loggers in the cave and at the surface. The data is collected in a one-hour interval. Recently, in 2019, a one- year project was started with the support of Biokovo Nature Park. The new partner is Emil Racoviţă Institute of Speleology (Romanian Academy, Romania). Besides the monitoring of microclimate, the aims of the project are geomorphological research, sampling, and monitoring of ice and snow dynamics. In two field trips, four samples of organic matter from several layers of ice were collected and sent to the laboratory for radiocarbon analyses. Additionally, for stable isotope analyses, 42 samples of ice were collected. The aim was to measure δ18O and δ2H in ice layers at different depths and identify the mechanism behind ice genesis (freezing of water vs. snow metamorphosis) and the possible climatic information embedded in the stable isotope composition of water.

ice cave, microclimate, monitoring, stable isotope

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