Heat and mass fluxes monitoring of El Chichón crater lake

El Chichón crater lake is characterized by important variations in volume (40,000 m3 to 230,000\nm3) and in chemical composition alternating between acid-sulfate and acid-chloride-sulfate composition\n(Cl�/SO4\n2� = 0�79 molar ratio). These variations in volume can occur very fast within less than a few weeks,\nand are not always directly correlated with the precipitation rate; the seepage rate of lake water is also\nan important parameter to consider in the lake mass balance. In this study, we present for the first time\ncontinuous physical data (temperature, depth, precipitation, wind velocity, solar radiation) of the crater\nlake registered by a meteorological station and two dataloggers. A heat and mass balance approach is\nproposed to estimate the heat and mass fluxes injected into the lake by the sublacustrine fumaroles and\nsprings. Tracing the evolution of such fluxes can be helpful to understand this highly dynamic lake and\noffers an efficient way of monitoring the volcanic activity. During the observation period, the hydrothermal\nheat flux was estimated to be 17-22 MW, and the mass flux 10-12 kg/s (error on both values of ± 15%).\nThese fluxes are mainly counterbalanced by the loss of heat and mass by evaporation, respectively of\n20-24 MW and 8-10 kg/s. Furthermore, the seepage rate of the lake waters was estimated and shown to\nbe a highly variable parameter (12-42 kg/s), depending on the lake surface. This new data set constitutes\na baseline to monitor the future activity of El Chichón volcano. In case of volcanic activity renewal, one\nof the first precursor signals would probably be the full evaporation of the lake.