A diatom-inferred record of cyclical drought and amelioration spanning the last two millennia in northern New Mexico, USA

Diatoms preserved in sediments are indicators of climate change.  As part of a cross-regional comparison of climate change, we cored the sediments of an alpine lake in New Mexico.  Our working hypothesis for this lake was the diatoms would show the largest response to climate change over the most recent century, particularly to the 1930s Dust Bowl and the 1950s drought.  However, our analyses suggest the lake has gone through a series of droughts and ameliorations over the last two millennia.  Between 1930-1430 YBP, the diatom community was dominated by alkalophilic species of Achnanthes and Staurosira, suggesting a wet climate.  Conversely, between 1430-1000 YBP, the diatom community included higher proportions of widely tolerant species of Aulacoseira, Cyclotella, and Cymbella, suggesting a change to drier conditions and increased evaporation.  Using these same profiles, we inferred that the climate was wet between 1000-585 YBP, dry between 585-215 YBP, and wet up to present day.  The bifurcation points of these trends (i.e., alkalophilic to tolerant, vice versa) correspond with prevailing paleoclimate reconstructions documented in the literature.  Furthermore, the nadir/apex of each profile curve (i.e., onset of transition from wet to dry, vice versa) also correspond with wet-dry climate boundaries reported in the literature.