State of the art clearly states that thermal conduction dominates cave temperature and underground karst temperature in most cases, although most professionals working in karst still ignore the important implications of this thermal transfer mechanism and its consequences. So, experiment 1, focus on the observation and model of thermal regime in a paradigmatic cave, to illustrate as an “educational” case used to help divulgating the implications of thermal diffusion in karst areas. In addition, we highlighted the role of the three phases of karst (rock, water and air) that help to conceal laboratory and field measurements of thermal diffusivities.
Our second experiment focus on the model of climate changes in the past during a full glacial cycle. Beyond thermal diffusivity, two main parameters control the transfer of heat: depth and period of the thermal anomaly. Thermal signals are transferred as waves and climate changes will reach a certain depth at different times depending on the period of the different waves in which the climate change is decoposed. We developed a model that for the first time quantifies the thermal amplitude and delay of the single waves being transferred. The results suggest that delay times for glacial anomalies lasted thousands of years and caused notorious thermal decoupling between the surface and the underground environments. The implications of the thermal decoupling impacted the oxygen isotope sginature of speleothems, the most popular proxy in speleothem paleoclimatology. So, thermal decoupling should not be ignored in speleothem paleoclimate interpretions.
In our third experiment, we simulated the evolution of underground temperature during the subsequent century considering five different scenarios of global warming. The transfer of global warming depends on the period of the thermal anomaly, so periods of thermal anomaly diverge among different scenarios. Since there is a delay between the signal at the surface and its record underground, the models show that all caves shallower than 10 m already record the global warming, whereas caves deeper than 100 m still do not record any thermal anomaly related to the global warming. These thermal changes will represent a major challenge to underground ecosystems, will change the geochemistry of groundwater and the conservation of cave art among other impacts. The underground thermal warming projections will affect industries such as tourist caves, wine cellars, mines, etc. These simulations might be useful to plan the future of their business, and if necessary, to start investing in research and development programs or in known methods to ameliorate the impact of global warming.
