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

尽管野火发生的频率和强度都在明显增加，但人们对加州火灾、气候变暖和降雨变化之间的关系仍然知之甚少。该项目将定义过去7万年气候变化与加州野火行为之间的关系。这将通过监测加州的洞穴和评估洞穴矿床中保存的气候变化和野火的证据来完成。这些沉积物被称为石笋，能够记录过去数千年到数万年的环境变化。一个将气候、洞穴和野火过程联系起来的环境模型将被开发出来，这将促进对气候和火灾信号如何在石笋中存档的理解。该模型还将用于在单个洞穴遗址和整个加利福尼亚州的洞穴样带中建立气候-火灾关系的强大重建。总的来说，这项研究将有助于构建该地区气候如何响应全球气候变化（包括变暖）以及这些变化如何影响野火行为的连贯图景。其他可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软件。一群不同的早期职业科学家、本科生和研究生将通过该项目接受纵向和横向整合的培训和指导计划“C3 -加州气候变化”的培训。该项目将测试三个假设，这些假设的主要目标是在各种时间尺度和背景气候状态下，包括没有或最小人为影响的时期，调查加州火灾易发地区的区域水文气候条件与野火之间的关系。这将通过解决四个研究目标来实现。首先，将通过监测代表CA不同气候条件的三个喀斯特系统，开发一套基于过程的“地表到石笋”的水文气候和火灾示踪剂演化理解。该组件将进一步校准有希望的新代用物（delta-44Ca， 87Sr/86Sr和一套生物标志物），这些代用物迄今已应用于少数喀斯特系统。其次，构建新一代多代理喀斯特系统模型，利用现有代理系统模型，将水文气候和火灾代理与其一系列环境和生态驱动机制联系起来。第三，将开发一套可比较的方解石、包裹体流体和生物标志物代用记录，包括新的水文和火灾代用记录，用于定义加利福尼亚州纬度和沿海至内华达山脉样带的10个石笋。第四，将使用贝叶斯反演进行特定地点和区域代理模型比较，以产生数据驱动的加利福尼亚州过去70 ka的水文气候和火灾活动的定量重建。总的来说，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。

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.