An Isotope-Enabled Data Assimilation System for the Last Millennium over South America

The scientific objectives of this project are to: i) quantify the spatiotemporal characteristics of the South American summer monsoon (SASM) and its relationship with the Atlantic Intertropical Convergence Zone during the Little Ice Age; ii) constrain the relative roles of the Pacific zonal sea surface temperature (SST) versus Atlantic meridional SST gradients in influencing the SASM over the Last Millennium (LM); iii) assess the added value of proxy assimilation when compared to the standalone model prior; iv) investigate the role of external forcing vs. internal variability in shaping the monsoon climate over the LM: v) assess the model-dependence of isotope-enabled data assimilation products: and vi) quantify when and how future monsoon projections emerge outside of the historical constraint placed by data assimilation (DA) reconstructions. Precipitation from SASM is critically important for environmental services that sustain socioeconomic activities, but future changes in monsoon rainfall remain highly uncertain. While the region’s paleoclimatic network has been steadily improving, so far the data has not been harnessed in a quantitative way that would allow putting current and future projected changes in a long-term context. To address this shortcoming the researchers will develop an isotope-enabled DA product for South America, covering the LM. By creating such an isotope-enabled reconstruction, the researchers seek to diagnose changes in isotopic composition and hydroclimate across the region within a framework that is dynamically and physically consistent. The potential Broader Impacts include the potential for greater understanding of South American hydro-climate against the backdrop of modern environmental impacts in the region, support for a graduate student and an early-career scientist as a post-doctoral scholar, and outreach activities. 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.