  Cave climatology and its impact on contemporary biogeochemical cycles are
still poorly documented. Ventilation in karst environment plays a fundamental
role in these two fields and its understanding could bring elements to study
them. However, only a few cavers have tried to understand and describe it, very
often in a qualitative way or by theoretical approaches. The aim of this study
is to test physical concepts with empirical data. For this purpose, a
ventilation model has been built and compared with field temperature and air
velocity measurements in the Milandre Cave Laboratory (Switzerland). The model
explains about 95% of the measured airflow thus confirming the major role of
temperature on the air dynamics. However, these first results also reveal that
the measured winter air flow is lower than predicted by the model and that the
air flow reversal occurs at a lower temperature than anticipated. Combined with
a forced ventilation experiment these results underline the influence of the
atmospheric composition (particularly the water vapor and concentration in
CO$_2$ and O$_2$), waterflow rates and network geometry on the air flow. This
work paves the way for a better quantification of heat and mass fluxes in
relation to underground ventilation.
