Temperature Regime, Dynamics and Water Balance of Two Crater Lakes in the Nevado de Toluca Volcano, Mexico

Abstract

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.