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

北美西南部是世界上气候最敏感的地区之一，其水文气候具有内在的多变性。大量证据表明，在末次冰期和全新世期间，该地区的水文气候在次年代际到千年尺度上反复发生了大规模的变化，但驱动这种变化的机制仍不确定。在这种过去的变率和未来气候变化的潜在幅度的背景下，需要对水文气候对扰动的响应和潜在的驱动机制有一个精确的理解。研究小组的目标是生成一套多代用方解石和流体包裹体的记录，在次年代用到百年代用的尺度上进行解析，这些石笋来自加州内华达山脉中部和南部，跨越了最后一次冰川消融到全新世。通过整合高精度铀钍测年、洞穴监测、多石笋记录和地球系统建模（单强迫水同位素跟踪模拟），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记录在石笋代理记录中；(2)在过去21000年不断变化的环境强迫背景下，应用这些知识来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沿海和北部开发的互补石笋记录相结合，将允许对影响西南太平洋地区风暴路径行为和降水模式的机制进行区域扩展调查。将数据模型与21-ka以来新的同位素支持的瞬态气候演化模拟（iTraCE-21ka模型）进行比较，将进一步了解美国西部气候对不同强迫的全球驱动因素和响应时间。综合洞穴监测-石笋代用物-水同位素模拟方法可以提供：(1)深入了解气候和喀斯特过程如何印记石笋代用物记录；(2)对美国西部古降水如何响应不断变化的气候条件进行定量约束。潜在的更广泛影响（bi）包括三项外展活动，将代表性不足的高中生和本科生纳入到Sierran石笋项目中，并将研究结果发布给公众。(1)一个由8名本科生组成的团队将通过在加州大学戴维斯分校（C3Climate Change in California）开展垂直整合项目（vertical integrated Project， VIP）正式融入研究。该项目由赫尔姆斯利慈善信托基金向VIP财团（UCD是参与的16所大学之一）提供资助，将包括每周研讨会、同伴指导和基于团队的洞穴监测研究。(2)将为Vacaville （CA）高中开发气候科学基础课程，这是一所西班牙裔服务机构。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（Sierra Nevada Recreation Corporation）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。内华达山脉娱乐公司拥有两个用于研究的塞拉利昂洞穴。该项目还将包括对研究生教育的支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.