What is the impact of increasing boreal forest fires on Arctic climate and sea ice?

北方森林火灾的增加对北极气候和海冰有何影响？

• 批准号: 2337045
• 负责人: Edward Blanchard-Wrigglesworth
• 金额: $ 34.33万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-04-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2337045&HistoricalAwards=false
• 关键词: What; impact; increasing; boreal; forest

Boreal forests cover large areas of northern Asia and North America, mainly over Siberia, Canada, and Alaska. In recent years, these forests have been affected by an increase in fires, caused in part by warmer summers and less snow in the spring. These fires emit large amounts of smoke which can be blown by winds northward to the Arctic. Once this smoke gets to the Arctic, it can both cool the climate by reflecting sunlight, but also warm it (if the smoke is nearer the surface, or if the small smoke particles reach the ice and snow on the surface, as they can darken it and absorb more sunlight). As we expect temperatures to continue to warm everywhere on the planet, it is likely that large boreal fires will continue and even become more common. We plan to study the impact that the smoke may have on Arctic climate and sea ice using climate models. In the past, these climate models have not taken into consideration an increase in these boreal fires, and our work will help us determine if this is an important process to get right for understanding future changes in Arctic climate and sea ice. As we prepare for the next generation of climate models that help inform the United Nations’ panel on climate change, our results will also help highlight the importance boreal forest fires may have for climate change in the Arctic.Biomass burning from boreal forest fires can impact Arctic climate and sea ice via the atmospheric transport of aerosols, particularly black carbon, from source regions into the Arctic. While in the atmosphere, aerosols can have either a positive (warming) or negative (cooling) radiative forcing, depending on their elevation. Black carbon can also be deposited onto the sea ice or snow at the surface, where it has a positive radiative forcing because it darkens it and absorbs more sunlight. While fully coupled climate models simulate these processes, the amount of biomass burning is prescribed as a set forcing. In the most recent set of climate model runs that help inform the United Nations’ panel on climate change, simulations from 2015 to 2100 used fixed projections of boreal biomass burning emissions that did not anticipate an increase in forest fires. However, in the real world we have observed a dramatic increase in boreal biomass burning over the last 10 years, in part due to warmer summers and reduced spring snow cover (which itself is driven by warmer springs), and the emissions of black carbon are already more than double what the climate models used over 2015-2100. We plan to study the impact that an increase in boreal biomass burning has on Arctic climate and sea ice by running climate model simulations that prescribe an increase in aerosol emissions based on the recent observed growth in these fires. We also plan to study the impact that wind patterns have on the transport of smoke from boreal forest fires, as it is known that certain weather patterns can promote the likelihood of forest fires. This coupled interaction between weather and fires is currently missing in climate models, and our work will help us determine how important winds, in addition to the amount, severity and seasonality of fires are in determining how much black carbon is transported into the Arctic. Our results will serve to inform stakeholders of the importance of boreal forests for Arctic climate in the coming decades. As the community prepares for the next round of climate model simulations, our results will help inform the modeling community on the importance of both increasing boreal forest fires and the interaction of fires and winds on Arctic climate and sea ice.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.

北亚森林覆盖了北亚和北美的大面积，主要是西伯利亚，加拿大和阿拉斯加。近年来，这些森林受到火灾增加的影响，部分原因是夏季温暖而春季的降雪较少。这些火灾会散发出大量的烟雾，这些烟雾可以被北极向北吹来。一旦这种烟雾到达北极，它既可以通过反射阳光来冷却气候，又可以加热气候（如果烟雾在表面附近，或者小烟颗粒到达表面上的冰和雪，因为它们可以使其变黑并吸收更多的阳光）。正如我们期望的温度将继续在地球上任何地方温暖下来，大火可能会继续，甚至变得更加普遍。我们计划使用攀岩模型研究烟雾对北极气候和海冰的影响。过去，这些攀岩模型没有考虑到这些北方火灾的增加，我们的工作将帮助我们确定这是否是了解北极气候和海冰未来变化的重要过程。当我们为下一代气候模型做准备帮助联合国气候变化的小组中，我们的结果还将有助于强调北方森林火灾对北极气候变化的重要性。北极森林火灾燃烧的生物量可能会影响北极气候和海冰通过空气中的大气运输，尤其是黑色碳，尤其是黑色碳，尤其是从源代码中。在大气中，气溶胶可以取决于其升高，可以具有阳性（变暖）或负（冷却）辐射强迫。黑碳也可以沉积在地面上的海冰或雪上，在那里它具有正辐射强迫，因为它使其变黑并吸收更多的阳光。尽管完全耦合的气候模型模拟了这些过程，但将生物量燃烧的量作为集合强迫。在最近的气候模型运行中，有助于通知联合国气候变化的小组，从2015年到2100个使用了北方生物量燃烧排放的固定项目，这些预测不会增加森林大火。但是，在现实世界中，我们观察到过去十年来北方生物质燃烧的急剧增加，部分原因是夏季较温暖和春季雪覆盖（本身是由温暖的弹簧驱动），而黑碳的排放量已经是2015 - 2100年以上使用的攀岩模型的两倍以上。我们计划通过运行攀岩模型模拟来研究北极生物量燃烧对北极气候和海冰的影响，这些模型根据最近观察到的这些火灾的增长而开出了气溶胶排放的增加。我们还计划研究风向模式对北方森林大火烟的运输的影响，众所周知，某些天气模式可以促进森林大火的可能性。气候模型中目前缺少天气和火之间的这种耦合相互作用，我们的工作将帮助我们确定除火灾的数量，严重性和季节性在确定多少黑碳被运输到北极的情况下，风的重要性，严重程度和季节性。我们的结果将有助于在未来几十年中告知利益相关者北方森林对北极气候的重要性。当社区为下一轮气候模型模拟做准备时，我们的结果将有助于告知建模社区的重要性，即增加北方森林大火的重要性以及对北极气候和海冰的火灾和风的相互作用。这奖反映了NSF的法定任务，并通过使用基金会的知识优点和广泛的criperia来评估，通过评估来获得珍贵的支持。