Rainfall, Ecosystems, and Fire in Warm Late Neogene Climates of the Lake Baikal Region

气候变化使得严重的干旱和持续的热浪更容易引发野火。这些大火摧毁了西伯利亚和加拿大的当地社区，而西伯利亚、加拿大、西欧和美国的大城市则被烟雾笼罩。此外，北方地区在土壤中储存了大量的碳，如果这些碳被释放到大气中，将加速全球变暖。北方森林频繁发生的野火通过将森林变成草原和加速永久冻土融化而导致碳释放。气候模型预测了巨大的生态系统变化，到21世纪末，北方森林将被广阔的草原所取代，新的温带落叶森林生态系统将占据西伯利亚的大部分地区。然而，野火的区域差异和卫星观测的短时间跨度使得难以验证这些模式预测。该项目利用地球过去的温暖时期来测试气候模型对西伯利亚在温暖气候下的水文气候、火灾和植被覆盖的预测，比如预计到21世纪末。模型将通过与保存在俄罗斯贝加尔湖钻芯中的有机和矿物化石中过去840万年的气候、植被和野火记录进行比较来测试。该项目的主要目的是生成新的古气候记录。本研究更广泛的影响是，模型的验证将使更准确地预测未来的碳排放以及西伯利亚未来几十年的人类可居住性和经济潜力成为可能，并对区域安全产生潜在影响。该项目还将支持本科生在联邦指定的西班牙裔服务机构进行研究。该项目将基于气候模型预测和对近期气候和野火趋势的研究，检验两个假设。第一，在温暖的气候条件下，西伯利亚的生长季节延长，降水更均匀，将通过对植物蜡氢同位素（降水同位素代用物）和支链甘油二烷基甘油四醚（温度代用物）的配对分析来验证。第二，贝加尔湖地区的火灾状况是温度、水文气候和生物群系的函数，将通过对与植物蜡氢同位素和支链甘油二烷基甘油四醚测量相同样品中的多环芳烃和木炭（火灾代用品）的配对分析来验证。这些数据的时间序列将揭示过去840万年西伯利亚气候、植被和野火对全球气候趋势的区域响应。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。

Climate change makes acute droughts and prolonged heat waves that stimulate wildfires more common. These fires have devasted local communities in Siberia and Canada while blanketing large municipalities in Siberia, Canada, Western Europe, and the United States with smoke. Furthermore, boreal regions store huge amounts of carbon in soils that, if released to the atmosphere, would accelerate global warming. Frequent wildfires in boreal forests lead to carbon release by shifting forest to grasslands and by accelerating permafrost melt. Climate models predict dramatic ecosystem changes, with boreal forests replaced by extensive grasslands and a new temperate deciduous forest ecosystem occupying much of Siberia by the end of the 21st century. However, regional differences in wildfires and the short time span of satellite observations make it difficult to verify these model predictions. This project uses warm periods in Earth’s past to test climate model predictions of hydroclimate, fire and, vegetation cover in Siberia in warm climates, such as expected by the end of the 21st century. Models will be tested by comparison to a record of past climate, vegetation, and wildfire over the past 8.4 million years that is preserved in organic and mineral fossils in a drillcore from Lake Baikal, Russia. The primary purpose of this project is the generation of this new paleoclimate record. The broader impacts of this study are that validation of models will make possible more accurate forecasts of future carbon emission as well as the human habitability and economic potential of Siberia in coming decades, with potential ramifications for regional security. The project will also support undergraduate research experiences at a federally designated Hispanic-serving institution.This project will test two hypotheses, based upon climate model predictions and studies of recent climate and wildfire trends. The first, that growing season lengthens and precipitation is more equable in Siberia under warm climate conditions, will be tested by paired analyses of plant-wax hydrogen isotopes (precipitation isotope proxy) and branched glycerol dialkyl glycerol tetraethers (temperature proxy). The second, that fire regime in the Lake Baikal region is a function of temperature, hydroclimate, and biome, will be tested by paired analyses of polycyclic aromatic hydrocarbons and charcoal (fire proxies) in the same samples as the plant-wax hydrogen isotope and branched glycerol dialkyl glycerol tetraether measurements. Timeseries of these data will reveal the regional response of climate, vegetation, and wildfires in Siberia to global climate trends over the past 8.4 million years.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.