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

美国西南部是一个干旱多发的地区，有几个不断增长的人口中心，这些中心已经具有可用水边际的特点。大多数模型预测，气候变化将加剧该地区的水资源短缺，但由于区域地形复杂，模拟西南地区的水气候动态仍然是粗分辨率全球气候模型的挑战。该项目将通过模拟西南地区极端气候时期(距今18000年至147000年)的降雨量变化和相关的大气动力学来应对这一挑战。此外，第二套模式模拟将调查在大西洋经向翻转减弱这一主要洋流系统的预测情景下二十世纪末西南部的降雨反应。这将使用一种新的多尺度地球系统建模方法来实现，该方法将解决复杂区域地形上的精细动力学特征以及与气候系统的大尺度特征的相互作用。这些模拟部分将(1)提供一个机会，以确定大气对过去气候变化的响应，并更好地了解该地区目前和未来降雨变化所涉及的动力机制；以及(2)将促进对未来大西洋子午线翻转环流(AMOC)预计下降对美国西南部水文气候影响的理解。在模拟框架中增加水同位素示踪剂，将有助于通过与区域水文气候指标(例如，洞穴)的直接比较，研究AMOC与西南水文气候的遥相关关系。总体来说，模拟部分探索了气候变化的过去和未来间隔，以更好地了解该区域现在和未来降水变化所涉及的动力机制。潜在的更广泛的影响包括通过调查过去和未来气候中的AMOC和降雨量之间的联系，更好地理解大西洋经向翻转在区域水文气候中的作用。研究和推广活动将为早期职业科学家提供科学和专业发展。这包括与该地区的水资源利益攸关方进行科学协作和联网、指导和科学交流。外展活动将促进科学家与西南水资源管理者和利益相关者之间的公开讨论，以确保研究具有超出学术界的价值。此外，PI将通过研究生研讨会和实验室会议参与和促进地球科学和STEM中关于心理健康的讨论。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.