Impact of vegetation on historical North American droughts and the implications for a future greenhouse world

Abstract:

Plants are an important determinant of future freshwater availability due to their countervailing and poorly-constrained water-use responses to warming and CO₂. Here we analyze the CMIP6 class of land surface ‘reanalyses’ that participate in the Land Surface, Snow and Soil Moisture Intercomparison Project (LS3MIP) experiments and their representation of coupled vegetation-drought interactions during real-world North American severe droughts. We analyze how model diversity in vegetation processes impact soil moisture and runoff during these drought events as plants minimize their water losses while also sustaining growth. We place these LS3MIP real-world drought analyses in the context of the carbon-climate-water-vegetation processes and feedbacks that are simulated by the same land surface models in the Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP). We subsequently assess whether model diversity in carbon feedbacks (from C4MIP) account for model diversity in vegetation processes during the real-world drought events (from LS3MIP), thus informing how different model representations of vegetation impact the realism of simulated real-world North American droughts. Results lay the groundwork for thorough evaluations of systematic biases in vegetation-drought coupling within CMIP6 models, therefore helping to interpret their projections of future drought and aridity.