Collaborative Research: P2C2--Bridging the Gap from Northern Iberia to Northwest Africa to Reconstruct Atmospheric Dynamics and Hydroclimate for the Last 2,500 Years

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The Mediterranean region is identified as a climate change hot spot. Recent observations, including increased fire activity in 2017, suggest that aridity in the Iberian Peninsula is already increasing. This multi-institutional team of researchers seeks to provide a spatial and temporal context for on-going and future climatic changes in this region by constructing a 2,500-year-long history of hydroclimate variability from precipitation-sensitive stalagmites formed in caves in central and southern Portugal. Rainfall in Iberia is strongly correlated to the strength of the Azores sub-tropical high-pressure system, and these cave sites lie at its climatological epicenter. Specifically, this project aims to bridge the hydroclimate knowledge gap for the last 2,500 years using sub-decadally resolved, multi-proxy stalagmite records (carbon and oxygen stable isotope ratios, trace element abundances, growth laminae, and high precision Uranium/Thorium dating) from cave sites in central and southern Portugal. Based on measuring, counting and comparing the uppermost Uranium/Thorium age from one stalagmite, these laminae appear to be annual in nature. Resulting data will be combined and evaluated with similarly-resolved hydroclimate-sensitive records from northern Iberia (Spain) and northwest Africa (Morocco), creating a latitudinal transect that will allow spatial and temporal constraints to be placed on the Azores HighThis research could also provide a significant spatial bridge between the only existing high-resolution paleo-hydroclimatic reconstructions (northern Morocco and northern Spain) from this zone. Together, these time series will allow for a more comprehensive evaluation of dynamical changes in the regional climate system through time, particularly in the spatial extent and intensity of the Azores High.The state of the atmospheric circulation in the North Atlantic region during recent millennia, and particularly medieval times, remains the subject of considerable debate in both proxy- and model-based studies. Of particular interest is the North Atlantic Oscillation (NAO), an atmospheric dipole between the Iceland low and the Azores high, which is strongly linked to regional inter-annual precipitation variability in Western Europe and northwest Africa through the routing of storms tracks. Dynamics of the NAO and the Azores High are poorly understood prior to the late 19th century, and as a result, the drivers of NAO/Azores High dynamics have not been adequately explored. An ideal place to address these deficiencies is central and southern Portugal, where few, if any, high-resolution records exist.The potential Broader Impacts (B.I.) includes the potential to transform the understanding of the nature and drivers of past Iberian hydroclimate variability, and through comparison with model simulations, how it may respond to future anthropogenic forcing. As such, the development and synthesis of these high resolution and precisely dated records will be of value to the broad climate/paleoclimate communities. All data produced as part of this project will be made publicly available and archived on community websites. The project unites a diverse, internationally recognized team of researchers from major research institutions (Iowa State University, Woods Hole Oceanographic Institution, University of New Mexico) and liberal arts colleges (Cornell College, Union College) to apply multi-disciplinary approaches to addressing long-term hydroclimate dynamics. This work will involve the training of a PhD student already in residence at Iowa State and at least eight undergraduate researchers in state-of-the-art climate reconstruction and modeling techniques. A component of data collection in Portugal will involve citizen-based science at a local tourist cave and with regional caving groups.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.