Session: Benchmarking & cross-cutting Group 1 (Isotope modelling, COMPARE)
Author: Carrie Morrill / email@example.com / Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder and NOAA’s National Centers for Environmental Information, Boulder CO 80305
Lake level information has long offered a critical qualitative model-data comparison for past moisture conditions. We extend this comparison quantitatively, using output from coupled climate models participating in the Coupled Model Intercomparison Project (CMIP5) and forward models of lake and drainage basin water balance to simulate Last Glacial Maximum (LGM) lake levels in nine drainage basins in western North America. During the last glacial and early deglacial periods, large lakes expanded in many drainage basins across this currently-arid region. The high concentration of well-dated shoreline records here make quantitative model-data comparison feasible. The CMIP5 models achieve varying degrees of success in driving the forward models to match observed LGM lake level changes, as measured in both data and models by the ratio of lake area to drainage basin area. Those models that successfully match observations are distinguished by large decreases in lake evaporation and basin evapotranspiration at LGM due to cooling, and also yield the greatest temperature increases in future climate projections. Our results establish the important role of temperature in determining past moisture conditions over western North America and support the strong likelihood of drying in the future.