Collaborative Research: P2C2--Multi-Time-Scale Climate Dynamics in California (CA): An Integrated Multi-Proxy Stalagmite, Monitoring, and Modeling Approach

北美西南部(SWNA)是世界上气候最敏感的地区之一，具有固有的多变的水文气候。有许多证据表明，在上一次冰川周期和全新世期间，该区域的水气候在亚十年到千年尺度上反复发生大规模的制度变化，但推动这种变化的机制仍然不确定。鉴于过去的可变性和未来气候变化的潜在规模，需要对水气候对扰动的反应和潜在的驱动机制有更深入的了解。该研究小组的目标是为加利福尼亚州内华达山脉中部和南部的四个石笋生成一套多重代理方解石和流体包裹体记录，这些记录可以在十年到百年的尺度上分辨出来，这些石笋跨越了最后一次冰川消融直到全新世。通过将高精度铀-钍测年、洞穴监测、多石笋记录和地球系统模拟(单强迫水同位素跟踪模拟)相结合，研究小组将(1)评估北太平洋风暴路径行为和由此产生的降水信号如何被存档在石笋代理记录中，以及(2)应用这一知识在过去21,000年不断变化的环境作用力的背景下研究这种降水响应的机制。将新的内华达山脉记录与正在为加利福尼亚州沿海和北部开发的补充石笋记录相结合，将使对影响SWNA风暴路径行为和降水模式的机制进行区域扩展调查成为可能。将数据模型与新的21-ka模拟以来的同位素启用的瞬变气候演变(iTRACE-21ka模型)进行比较，将进一步深入了解全球气候驱动因素和美国西部气候对不同强迫的响应时间。一个集成的洞穴监测-石笋代理-水同位素模拟方法可以提供(1)气候和喀斯特过程如何影响石笋代理记录的洞察，以及(2)关于美国西部古降水如何响应不断变化的气候条件的迫切需要的定量约束。潜在的更广泛的影响(B.I.)包括三项外联活动，将代表性不足的高中生和本科生纳入Sierran石笋项目，并向公众分发调查结果。(1)一个由8名本科生组成的团队将通过加州大学戴维斯分校的垂直整合项目(VIP)(加州的C3气候变化)正式纳入研究。该项目由赫尔姆斯利慈善信托基金向VIP联盟(UCD是参与的16所大学之一)提供的赠款支持，将包括每周研讨会、同行指导和基于团队的洞穴监测部分研究。(2)将为西班牙裔服务机构瓦卡维尔(CA)高中开发以气候科学为基础的课程。该课程将整合石笋研究的各个方面，并以培养批判性思维技能为目标。(3)将为内华达山脉娱乐公司(两个Sierran洞穴的所有者)建造一个互动洞穴展览，包括虚拟现实研究之旅和3-D石笋重建。该项目还将包括对研究生教育的支持。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。

Southwest North America (SWNA) is one of the world's most climatically sensitive regions with inherently variable hydroclimate. Much evidence exists for repeated, large regime shifts in this region's hydroclimate at the sub-decadal to millennial-scale during the last glacial cycle and Holocene, but the mechanisms driving this change remain uncertain. In the context of this past variability and the potential magnitude of future climate change, a refined understanding of the hydroclimate response to perturbation and of the underlying driving mechanisms is needed. The research team aims to generate a set of multiproxy calcite and fluid inclusion records, resolved at the sub-decadal to centennial-scale, for four stalagmites from the central and southern Sierra Nevada, CA that span the last deglaciation through Holocene. By integrating high-precision Uranium-Thorium dating, cave monitoring, multi-stalagmite records, and Earth system modeling (single-forcing water-isotope tracking simulations), the research team will (1) evaluate how North Pacific storm track behavior and the resulting precipitation signal is archived in the stalagmite proxy records, and (2) apply this knowledge to investigating the mechanisms underlying this precipitation response in the context of the changing environmental forcings of the past 21,000 years. Integration of the new Sierra Nevada records with complementary stalagmite records being developed for coastal and northern CA will permit a regionally expansive investigation of the mechanisms influencing storm track behavior and precipitation patterns in SWNA. Data-model comparisons with the new isotope-enabled Transient Climate Evolution since 21-ka simulations (iTraCE-21ka model) will provide further insight into the global drivers and response time of climate in the western U.S. to different forcings. An integrated cave monitoring-stalagmite proxy-water isotope modeling approach could provide (1) insight into how climate and karst processes imprint stalagmite proxy records, and (2) much needed quantitative constraints on how paleo-precipitation in the western U.S. responded to evolving climate conditions.The potential Broader Impacts (B.I.) include three outreach activities to integrate under-represented high school and undergraduate students into the Sierran stalagmite project and distribute the findings to the public. (1) A team (n=8) of undergraduate students will be formally integrated into the research through the development of a Vertically Integrated Project (VIP) at UC Davis (C3Climate Change in California). This program, supported by a grant from the Helmsley Charitable Trust to the VIP Consortium (UCD is one of 16 universities that participate), will involve weekly seminars, peer-mentoring, and team-based research in the cave-monitoring component. (2) A climate science-based curriculum will be developed for Vacaville (CA) High School, a Hispanic serving institution. The curriculum will integrate aspects of the stalagmite study and target development of critical-thinking skills. (3) An interactive cave exhibit involving a virtual reality research tour and 3-D stalagmite reconstructions will be built for the Sierra Nevada Recreation Corporation (owner of two of the Sierran caves targeted for study). The project would also include support for graduate education.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.