OPP-PRF: Assessing the relationship among fire, temperature, and precipitation in the Arctic during the Pleistocene

气温上升与大气中二氧化碳（CO2）浓度增加有关，正在全球范围内引发更多火灾事件，包括在北极地区。北极火灾事件具有区域性影响，包括将植物群落改变为更易燃的植物群落。此外，燃烧先前冻结的北极土壤可以释放储存的碳，向大气中增加更多的二氧化碳。一个地区野火的强度和数量主要受温度和降水的控制。气候模式可以很好地预测未来温度，但区域降水数据有限，这妨碍了准确预测北极野火的能力。这项研究将野火频率与过去不受人类活动影响的温度和降水进行比较。研究结果可用于改进降水对火灾频率影响的北极区域气候模式。这项研究的结果将传达给决策者，以协助他们做出应对未来变暖的决策。该项目将制作与北极气候变化和火灾有关的教育材料和实践科学项目，通过虚拟教室向全国各地的小学生推广。该项目将通过实验室工作、会议演示和Eureka！马萨诸塞州大学的暑期科学营，邀请12-18岁的女孩探索STEM领域。据预测，随着气温上升，北极地区的火灾干扰会增加，而降水也会影响火灾的频率和强度。未来的预测显示气温、降水和火灾事件将会增加。然而，气候模型在重建降水方面的能力有限，这抑制了对火灾频率的估计。此外，目前还不清楚降水是火灾频率的主要驱动因素，还是与气温上升同时起作用。先前对北极地区过去火灾的评估得出了截然相反的结果，即更潮湿和更干旱的条件都与火灾的增加有关。为了解决这个问题，需要更多的降水记录，排除人为火灾的影响，以限制潜在的反馈。本研究将利用有机地球化学技术，通过重建整个更新世的降水、温度和火灾来研究北极气候的变化。海洋钻探计划站点647位于格陵兰岛南部附近，将被研究，因为该站点跨越了已知的间冰期，如海洋同位素阶段（MIS） 11和超级间冰期MIS 31-33。由三种不同的有机地球化学技术产生的海面温度（SST）将与燃烧生物质产生的化合物浓度进行比较，如多环芳烃（PAHs）和左旋葡聚糖。这些数据将允许检查与温度历史相关的野火增加的时间段。将海表温度和火生物标志物浓度与来自同一岩心的植物叶蜡的氢同位素（δ2H）进行比较，这将提供有关北极水分输送途径的额外信息。该研究将评估间冰期较高的温度是否会导致更多的水汽向极地输送，这反映在由于温度升高导致北极更湿润的条件而导致的水汽来源变化而更丰富的δ2H上。总的来说，使用多种代用物将产生跨越更新世冰期和间冰期的新记录，以评估北极地区温度、降水、湿源和火灾之间关系的变化。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。

Rising temperatures associated with increasing atmospheric carbon dioxide (CO2) concentrations are causing more fire events globally, including in the Arctic. Arctic fire events have regional impacts including changing the plant community to those that are more flammable. In addition, the burning of previously frozen Arctic soils can release stored carbon, adding more CO2 to the atmosphere. The intensity and number of wildfires in a region are controlled mainly by temperature and precipitation. Climate models can project future temperature well but regional precipitation data are limited which hampers the ability to accurately project Arctic wildfires. This study will compare wildfire frequency to temperature and precipitation during times in the past that were not influenced by human activity. The results can be used to improve regional Arctic climate models of precipitation impact on fire frequency. Results of this study will be communicated to policymakers to assist with decision making in response to future warming. The project will generate educational materials and hands-on science projects related to climate change and fire in the Arctic for outreach to primary school students around the country through virtual classrooms. The project will engage undergraduates through lab work, a conference presentation, and a workshop for the Eureka! Summer Science Camp at the University of Massachusetts which engages girls ages 12-18 to explore STEM fields. Fire disturbances are predicted to increase in the Arctic with rising temperatures while precipitation also impacts fire frequency and intensity. Future projections show increases in temperature, precipitation, and fire events. However, climate models are limited in their ability to reconstruct precipitation, which inhibits estimates of fire frequency. In addition, it is unclear if precipitation is the primary driver of fire frequency or if it works in tandem with rising temperatures. Previous assessments of past Arctic fires have produced contrasting results with both wetter and more arid conditions being associated with an increase in fire. To address this, more precipitation records that exclude the impact of human-induced fires are needed to constrain potential feedbacks. This research will investigate variability in Arctic climate through reconstructing precipitation, temperature, and fire throughout the Pleistocene using organic geochemical techniques. Ocean Drilling Program Site 647, located near southern Greenland, will be studied as this Site spans known interglacials such as Marine Isotope Stage (MIS) 11 and super interglacial MIS 31-33. Sea surface temperatures (SST) generated from three different organic geochemical techniques will be compared to concentrations of compounds produced by burning biomass, such as polycyclic aromatic hydrocarbons (PAHs) and levoglucosan. These data will allow examination of time periods of increasing wildfires in connection with the temperature history. The SST and fire biomarker concentration will be compared to hydrogen isotopes (δ2H) of plant leaf waxes from the same core, which provides additional information on moisture transport pathways in the Arctic. The study will evaluate if higher temperatures during interglacials result in more poleward moisture transport, which is reflected in more enriched δ2H due to changes in moisture source as increasing temperatures leads to wetter conditions in the Arctic. Overall, the use of multiple proxies will generate new records spanning both glacial and interglacial periods across the Pleistocene to assess variability in the relationships between temperature, precipitation, moisture source, and fire in the Arctic.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.