P2C2: Collaborative Research: Defining the paleoclimate-fire relationship in CA across temporal scales through integrated monitoring, stalagmite studies, and proxy system modeling

尽管野火的频率和强度明显增加，但加州(CA)火灾、变暖和降雨量变化之间的关系仍然知之甚少。这个项目将定义过去的气候变化和过去70,000年来加州野火行为之间的关系。这将通过监测加利福尼亚州的洞穴和评估气候变化和洞穴矿藏中保存的野火的证据来实现。这些沉积物被称为石笋，能够记录过去数千年到10000年的连续环境变化。将开发一个将气候、洞穴和野火过程联系起来的环境模型，这将促进对气候和火灾信号如何在石笋中存档的理解。该模型还将用于建立单个洞穴遗址和整个加利福尼亚州洞穴横断面的气候-火灾关系的稳健重建。总体而言，这项研究将有助于建立一个连贯的图景，了解该地区的气候如何应对全球气候变化，包括变暖，以及这些变化如何影响野火行为。其他交付成果包括所有石笋记录的开放获取、标准化数据库和社区可访问的软件。一批不同的早期职业科学家以及本科生和研究生将通过该项目接受培训，该项目使用一个纵向和横向整合的培训和指导计划--C3-加州的气候变化。该项目将测试三个假设，这些假设与调查加州火灾多发地区区域水文气候条件和野火之间的关系的主要目标有关，涉及各种时间尺度和背景气候状态，包括没有或最小程度的人为影响。这将通过解决四个研究目标来实现。首先，将通过对代表加利福尼亚州不同气候条件的三个喀斯特系统的监测，发展对一套水文气候和火灾示踪剂演化的基于过程的、从表面到石笋的理解。这一组成部分将进一步校准迄今为止应用于少数岩溶系统的有前景的新代用指标(Delta-44Ca、87Sr/86Sr和一套生物标志物)。其次，将建立下一代多代理岩溶系统模型，该模型利用现有的代理系统模型，并将水文气候和火灾代理与其环境和生态驱动因素套件机械地联系起来。第三，将为10个石笋开发一套类似的方解石、包裹体-流体和生物标志物替代记录，包括新的水文和火灾替代记录，这些记录定义了加利福尼亚州内华达州的纬度和沿海到内华达山脉的断面。第四，将利用贝叶斯反演进行特定地点和区域代理模型的比较，以产生过去70ka以来加州水文气候和火灾活动的数据驱动的定量重建。总而言之，这项研究将为未来的气候建模工作提供基础，重点是限制美国西部水文气候变化和火灾活动的驱动因素。该奖项反映了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。

Despite observable increases in the frequency and intensity of wildfires, the relationship between fire, warming, and rainfall variability in California (CA) remains poorly understood. This project will define the relationship between past climate change and wildfire behavior in CA over the last 70,000 years. This will be accomplished by monitoring caves in CA and by assessing evidence of climate change and of wildfires preserved in cave mineral deposits. These deposits, called stalagmites, are capable of documenting past environmental changes continuously over 1000s to 10s of thousands of years. An environmental model that links climate, cave, and wildfire processes will be developed that will advance the understanding of how the climate and fire signals are archived in stalagmites. The model will also be used to build robust reconstructions of the climate-fire relationship at individual cave sites and for transects of caves across CA. Collectively, this research will contribute to building a cohesive picture of how climate in this region responds to global climate change, including warming, and how these changes influence wildfire behavior. Additional deliverables include an open-access, standardized database of all stalagmite records and community accessible software. A cohort of diverse early career scientists and undergraduate and graduate students will be trained through the project using a vertically and laterally integrated training and mentoring program, ‘C3 —Climate Change in California’.This project will test three hypotheses linked by the primary goal of investigating the relationship between regional hydroclimate conditions and wildfire in the fire-prone region of CA, over a variety of timescales and background climate states including periods with no or minimal anthropogenic influence. This will be accomplished by addressing four research objectives. First, a process-based, ‘surface-to-stalagmite’ understanding of the evolution of a suite of hydroclimate and fire tracers will be developed through monitoring of three karst systems representative of different climate conditions in CA. This component will further calibrate promising new proxies (delta-44Ca, 87Sr/86Sr, and a suite of biomarkers) that to date have been applied to few karst systems. Second, a next-generation, multi-proxy karst system model will be built that leverages existing proxy system models and links hydroclimate and fire proxies mechanistically to their suite of environmental and ecologic drivers. Third, a comparable set of calcite, inclusion-fluid, and biomarker proxy records, including novel hydrologic and fire proxies, will be developed for ten stalagmites that define latitudinal and coastal-to-Sierra Nevada transects in CA. Fourth, site-specific and regional proxy-model comparisons will be carried out using Bayesian inversion to produce data-driven quantitative reconstructions of the hydroclimate and fire activity in CA over the past 70 ka. Collectively, this research will provide the basis for future climate modeling efforts focused on constraining the drivers of hydroclimate change and fire activity in the western U.S.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.