Collaborative Research: P2C2--Medieval to Modern Climate Variability and Climate Change in the Great Plains

The general goal of the research is to develop moisture sensitive tree-ring chronologies from old-growth populations of Juniperus, Pinus, and Taxodium trees from within or near the Great Plains for in situ reconstructions of seasonal precipitation and the long-term soil moisture balance that together will constitute the Great Plains Drought Atlas (GPDA). Five gridded reconstructions that span the Great Plains at 0.5 degree resolution will be developed, including the Standardized Precipitation Index (SPI) for the spring and summer seasons, precipitation totals for spring and summer, and the summer Palmer Drought Severity Index (PDSI). The reconstructions will be designed for maximum length, with the goal of extending the moisture estimates into the Medieval Period when the climate appears to have been much warmer and drier. The GPDA will be used to test hypotheses concerning the magnitude of Great Plains drought and pluvial, the anthropogenic imprint on recent moisture trends in the Great Plains, and the possible multi-decadal regimes in the frequency of rapid-onset spring to summer flash drought over the Great Plains during the past 500- to 1000-years.The highest agricultural production in the United States occurs in the Great Plains, a region also subject to frequent drought, including the flash drought of 2012 that resulted in $30 billion in losses. Proxy tree ring and lake sediment data suggest that the instrumental record of precipitation and soil moisture may not be representative of the natural variability of severe droughts and prolonged wet intervals over the past millennium. Anthropogenic climate change may be contributing to wetter conditions in the Northern Plains and increasing dryness over the Southern Plains, a possible expression of the drying symptomatic of the expansion of the Hadley Cell and the weakening of the jet stream predicted by many climate models. These human-induced changes threaten to disrupt agriculture, energy production, and water use, and may be magnified by recurrent decadal moisture extremes witnessed in instrumental and paleoclimate records. Very few exactly dated, annual tree-ring chronologies are available from the mostly treeless Great Plains. The lack of data adds considerable uncertainty to the available reconstructions of moisture anomalies for this region. This project seeks to reduce the uncertainty by developing long tree-ring chronologies within and along the boundaries of the Great Plains to aid reconstruction of past drought and wetness in this critical agricultural region.The potential Broader Impacts (B.I.) include improvement in understanding climate processes involving drought and extreme events in the Great Plains regions that impact the highest agricultural production in the United States. Importantly, the project includes researchers and students from a regional Primarily Undergraduate Institution (PUI) which has strong ties to affected agricultural and tribal communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.