Impacts of recent climate variability (CA 100 yr) on a subtropical mid altitude lake

This study aimed to examine the recent evolution (∼1929–2016) of Lake Coatetelco, a subtropical mid-altitude lake using sediment records to infer changes in water level and trophic status and contrast them to geostatistical data as well as to the Atlantic Multidecadal Oscillation (AMO) and the El Niño/Southern Oscillation (ENSO), both known to have repercussions on the precipitation of the region. Analyzing diatom assemblages, Ti, P, N, Fe/Al ratio, Corg and satellite imagery enabled to characterize lake level and trophic changes across four aquatic zones. In ∼1929 (Zone I), precipitation anomalies and AMO index were positive, while diatoms and geochemistry indicated deep, low-salinity waters with high runoff. From 1940 to 1995 (zone II), precipitation anomalies and AMO index were generally negative, while lower Ti values and diatom assemblages indicated a lower water level accompanied by higher salinity and an increase in the trophic and anoxic condition of the lake. Between 1995 and 2011 (Zone III), precipitation anomalies and the AMO were positive. Correspondingly, Ti concentrations and diatom records indicated increased surface runoff, rising water levels, and a shift toward lower trophic levels and higher oxidation conditions. From 2011 to 2016 (Zone IV), runoff remained high until 2016, when reduced runoff and increased evaporation resulted in shallower, saltier water, with trophic levels rising again in this final year. This study found a strong positive correlation between the titanium record, precipitation, and the AMO index, highlighting the significant influence of climate modulators on rainfall patterns and, consequently, on drought periods in the region near Lake Coatetelco. This also emphasizes the reduced water levels and increase in salinity, trophic status and anoxic conditions during periods of low precipitation. On the other hand, during periods of increased humidity in the region, water levels rise, and salinity decrease. As water levels increase, the lake's trophic status tends to decline, and anoxic conditions become less pronounced.