Volcanic lakes are ecosystems in which thermodynamic processes have a complex relationship with atmospheric variables. This study presents the results of an analysis of the thermal regime and dynamics of two high-altitude tropical lakes located in the crater of the Nevado de Toluca volcano in Mexico, at an altitude of more than 2200 m above sea level. Joint meteorological and hydrological measurements taken in two adjacent lakes revealed strong diurnal fluctuations in water temperature, which are caused by wind-induced internal gravity waves and free seiches oscillations. During the daytime, heating occurs in the near-surface layer of the lakes, which creates a thermocline at a depth of 2–3 m, but it is washed out at night. The heat penetration into the lakes is significantly different due to differences in water transparency and algae density, despite the small distance of only 200 m between the lakes separated by a 100-m high lava dome. Temperature and level fluctuations were analyzed using spectral analysis. The numerical model used in Lake El Sol allowed for the first-ever evaluation of the circulation and the impact of wind circulation regimes on lake-level fluctuations. Analyzing such physical processes is crucial in assessing the chemical and biological processes occurring in this reservoir. Field measurements uncovered unexpected temperature changes near the lake bottom, along with heat exchange between the bottom water layer and bottom sediments (during winter, sediments emit heat to the water column). The estimated heat fluxes through the lake bottom were less than 0.3 W/m2 during winter and less than 0.1 W/m2 for the rest of the year.
High-mountain lakes are unique ecosystems with very few examples at tropical latitudes for experimentation. A two-year, high-frequency meteorological and water-column dataset from the crater of the Nevado de Toluca volcano, in Mexico, at an altitude of about 4200 m above sea level, allowed for the study of temporal changes in the thermal structure, water level, and water balance in the Lakes El Sol and La Luna, separated by about 500 m by a lava dome. Annual fluctuations in the water level of the lakes and calculations of the annual variability of the water balance showed that the lakes accumulated almost four times less water from rainfall than expected. Furthermore, the temperature measured at a depth of 15 cm in the bottom sediments of Lake El Sol revealed an unexpected warming during the cold season. Estimated heat fluxes through the lake bottom were less than 0.3 W m−2 during the winter and less than 0.1 W m−2 during the rest of the year. Although the variability of the hydrometeorological regime of high-mountain lakes remains relatively poorly understood, our results significantly improve the understanding of these complex processes of stratification and mixing in these unique lake ecosystems.
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