AGS-PRF: Hydroclimate Response of the Southwestern United States (US) to Past and Future Atlantic Meridional Overturning Circulation (AMOC) Weakening

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The U.S. Southwest is a drought-prone region that hosts several growing population centers, which are already characterized by marginal water availability. Most models predict that climate change will exacerbate water scarcity in the region but simulating hydroclimate dynamics in the Southwest remains a challenge for coarse-resolution global climate models due to the complex regional topography. This project will address this challenge through the simulations of the rainfall variability and associated atmospheric dynamics in the Southwest during a climate extreme period (between 18 to 14.7 thousand years before present). In addition, a second set of model simulations will investigate the end-twentieth century rainfall response in the Southwest under projected scenarios of Atlantic Meridional Overturning weakening, a major ocean current system. This will be accomplished using a novel multi-scale Earth system modeling approach that will resolve both fine-scale dynamical features over complex regional terrain and interactions with large-scale features of the climate system. These modeling components will (1) provide an opportunity to identify the atmosphere’s response to past climate changes and for improved understanding of the dynamical mechanisms involved in present and future rainfall changes in the region; and will (2) advance the understanding of the future impacts of a projected decline in Atlantic Meridional Overturning Circulation (AMOC) on hydroclimate in the U.S. Southwest. The addition of water isotope tracers in the modeling framework will permit investigation of AMOC teleconnections with Southwest hydroclimate through direct comparisons with regional hydroclimate proxies (e.g., speleothems). Collectively, the modeling components explore a past and a future interval of climate change to better understand the dynamical mechanisms involved in present and future precipitation changes in the region.The potential Broader Impacts include a greater understanding of the role of Atlantic Meridional Overturning in regional hydroclimate by investigating linkages between AMOC and rainfall in past and future climates. The research and outreach activities will provide scientific and professional development for an early career scientist. This includes scientific collaborations and networking, mentoring and science communication with water stakeholders in the region. The outreach activities will facilitate open discussions between scientists and Southwest water managers and stakeholders to ensure that research holds value beyond academic circles. Additionally, the PI will engage and facilitate the discussions on mental health in Geosciences and STEM through graduate seminars and lab-meetings.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.