Changes in late Pleistocene hydroclimate and lake level fluctuations at Lake Cochise, AZ

The Willcox basin, one of the only hydrographically closed basins in Arizona, has intermittently been home to a series of pluvial lakes from the late Pleistocene to present. However, limited work has been done to understand lake level fluctuations in this region, due to a lack of preserved shoreline features and paleoclimate proxies. Here, we use radiometric dates of shoreline sediments recovered from ancient Lake Cochise, located within Willcox basin, to constrain changes in lake levels from the Last Glacial Maximum (~21 ka) throughout the deglaciation. Additionally, we use carbonate clumped isotope thermometry, a thermodynamically based proxy, to estimate mean annual air temperature and the oxygen isotopic composition of lake water, and use these estimates in concert with mass balance modeling to constrain and quantify annual precipitation and evaporation rates. We also compare our proxy-derived estimates to climate model simulations, to assess the accuracy of models in simulating the response of hydroclimate change. Hydroclimate reconstructions at Lake Cochise will allow us to gain a better understanding of the factors that have influenced the water cycle in the American Southwest, and could provide insight into the accuracy of process depiction in models used to predict how anthropogenically induced climate changes will impact regional water availability.