Collaborative Research: P2C2--ICECAP (Ice Age Chemistry and Proxies) Phase 3: Investigating Fire Activity and its Implications for Climate Across Multiple Timescales

该项目旨在研究过去火灾活动的不同记录，以提高对火灾活动随时间和气候条件变化的理解。野火对区域和全球气候变化有很大影响。火灾影响碳储存、地球化学循环、当地水文、陆地蒸发、海洋施肥以及具有重要辐射意义的气体和气溶胶的排放。例如，火黑碳（BC）在冰雪覆盖的表面上的沉积会减少二氧化碳，导致冰雪融化，二氧化碳的进一步损失，以及随后的变暖。尽管火对地球大气系统的重要性，过去的火灾活动的知识是相对缺乏的。在过去的150年里，南极冰芯中的一氧化碳（CO）和BC的冰芯记录并没有显示出一致的趋势，而木炭记录和冰芯BC的趋势有时在更长的时间尺度上不一致。末次冰期的木炭和BC记录揭示了与Dansgaard/Oeschger（D-O）事件相关的巨大变化，但这些变化的气候影响尚不清楚。该项目的第一阶段涉及自1750年以来对野火活动和气候反馈的250年模拟的严格验证。 在获得对模型性能的信心后，研究人员将模拟野火活动和随后在理想化D-O事件的选定阶段的辐射强迫。 该项目的第二阶段包括分析BC尺寸分布的变化，作为格陵兰和南极现有冰芯中BC来源和运输过程的潜在标志。该项目的主要目标是：1）末次冰期和工业化前时期野火活动的可持续模型模拟; 2）量化野火对冰川至间冰期和工业化前至现代时间尺度上的区域和全球气候的影响。研究人员的目标是计算不断变化的火灾对气溶胶辐射强迫，雪/冰对流效应，海洋施肥和大气氧化能力的影响;和3）检查观察到的冰芯记录中BC颗粒大小的趋势，以评估运输过程的变化，因此大规模的气象过程在冰川期的气候突变。 该分析的主要工具将是由美国国家科学基金会（NSF）资助开发的冰期化学和代理（ICECAP）模型，其潜在的更广泛影响包括增强对温暖气候中火灾活动的理解，以帮助减少未来气候轨迹预测的不确定性。该项目将通过NSF教师研究经验（RET）在哈佛的两个夏天支持高中教师。 可再生能源技术的参与者将制定关于野火和气候的实践课程。该项目还将资助一名研究生和一名博士后研究员。

This project aims to examine the disparate records of past fire activity as a means to improve the understanding of variation in fire activity over time and climatic conditions. Wildfires have a large influence on regional and global climate change. Fires affect carbon storage, biogeochemical cycling, local hydrology, land albedo, ocean fertilization, and emissions of radiatively important gases and aerosols. Deposition of fire black carbon (BC) on snow and ice covered surfaces, for example, decreases albedo and leads to snow- and ice-melt, further loss of albedo, and subsequent warming. Despite the importance of fires to the earth-atmosphere system, knowledge of past fire activity is relatively scant. Ice-core records of carbon monoxide (CO) and BC in Antarctic ice cores do not show consistent trends over the last150 years, while trends in charcoal records and ice-core BC are sometimes at odds over longer timescales. Charcoal and BC records from the last glacial period reveal large variations tied to Dansgaard/Oeschger (D-O) events, but the climate implications of these variations are unknown.The first phase of the project involves the rigorous validation of a 250-year simulation of wildfire activity and climate feedbacks since 1750. After gaining confidence in model performance, the researchers will simulate wildfire activity and subsequent radiative forcing during selected phases of an idealized D-O event. The second phase of the project includes analyzing the variability in BC size distributions as a potential marker of BC sources and transport processes in existing ice cores from Greenland and Antarctica. The main objectives of the project are: 1) Validate model simulations of wildfire activity in the last glacial and preindustrial eras; 2) Quantify the impacts of wildfires on regional and global climate on glacial-to-interglacial and preindustrial-to-present-day timescales. The researchers aim to calculate the effects of changing fires on aerosol radiative forcing, snow/ice albedo effects, ocean fertilization, and the atmospheric oxidative capacity; and 3) Examine observed trends in BC particle size in the ice core record to assess changes in transport processes and hence large-scale meteorological processes over abrupt climate change during the glacial period. The main tool for this analysis will be the Ice-age Chemistry And Proxies (ICECAP) model, which was developed with prior NSF funding.The potential broader impacts include an enhanced understanding of fire activity in warm climates to help reduce uncertainties in future climate trajectory predictions. The project will support high school teachers during two summers at Harvard through the NSF Research Experience for Teachers (RET). Participants in RET will develop a hands-on curriculum on wildfires and climate. The project will also support a graduate student and a postdoctoral fellow.