engleski

Interaction of air and water dynamics in deep caves of Mt. Velebit, Dinaric karst, Croatia

Air and water dynamics observed in the deep caves of Northern Velebit Mt. present example of coupling effect of various processes in karst environment. Cave exploration provides unique opportunity to separately observe and study various processes and their interaction directly in the karst underground (in situ). Simplified model of cave air circulation and temperature profile/gradient modified by circulation characteristics is presented. Inward air circulation during cold weather and absence of significant circulation during hot weather produce significant imbalance in the cave T and surface mean annual T. Lower cave T is manifested by snow and ice accumulation in the parts of the cave affected by chimney effect. Ice melting and accumulating absorbs or releases significant flow of energy. Therefore, ice accumulation acts as an efficient thermal buffer which preserves cave T in the zone of accumulation at 0 °C. In that way cave acts as a cold air trap due to its specific morphology, producing negative thermal anomaly in karst massif. Specific cave climate characteristics can also alter karst groundwater temperature and dynamics. Air dynamics which effectively cools cave atmosphere and produces ice accumulation also cools water flowing through the cave and recharging karst aquifer system. It is possible that cumulative effect of cold air trapping induced by caves morphology has substantial effect on lowering T within karst massifs. Water at karst springs is usually considered to reflect average annual T of its watershed. Presented mechanism can effectively lower groundwater T in comparison to surface T, as can be seen on vadose water flows in the Lukina jama-Trojama cave. Results of the presented study show that air and water circulation characteristics in karst underground can be significantly altered by morphological characteristics of caves.

karst hydrogeology ; cave meteorology, air and water dynamics, Velebit Mt., Dinaric karst, Croatia

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