Hydrography of Crater Lake of Isabel Island, Nayarit, México

An observational campaign was carried out in the hypersaline Crater Lake of Isabel Island to explain the main factors of its hydrodynamics. Wind, temperature and relative humidity time series data were obtained from a weather station installed on the island, sea level atmospheric pressure data were obtained from North American Regional Reanalysis data from which, the seasonal pattern and diurnal breezes can be observed. CTD (Conductivity, Temperature, Depth device) surveys were conducted to analyze the hydrography, and a spectral analysis of temperature time series derived from a chain of thermistors anchored inside the volcanic lake was performed. The results show that the maximum temperature is found not in the first layers of water but at a depth of 1.8 m at 37.9 °C; while from 4 m of depth to the bottom, the temperature remains constant at 27 °C. The lower density water from rain flows into the lake, covering the surface layer of the lake and maintaining this temperature profile. The thermal changes in the first three meters of depth are due to the atmospheric influence and diurnal solar radiation and some strong wind events. To confirm this information, a calculation of heat fluxes through the lake surface was performed. Changes at greater depths are a consequence of the variations in the seasonal effects on the water column.