Collaborative Research: Bugs to clouds: Thawing permafrost, its microbes, and their possible role in Arctic climate feedbacks

在一个变暖的世界里，北极预计会变得多云多雨。由于北极变暖的速度是世界其他地区的两倍多，由此导致的云层变化随后会影响海冰范围、永久冻土融化以及区域和全球天气。然而，北极云的形成和演变仍然高度不确定，部分原因是人们对称为气溶胶的空气中颗粒的了解有限，这些颗粒是云的种子，特别是形成云冰晶的气溶胶。这些冰晶被称为冰核粒子（INPs），它们可能来自土壤、植物、海洋、湖泊和河流。特别是，人们对地球生物群系中INPs的来源和丰度知之甚少，但它可能对云冰的形成至关重要。气温升高还引发高纬度地区的永久冻土迅速和广泛融化，这对生活在这些地区的社区和野生动物产生了影响。永久冻土的融化还会释放温室气体，促进细菌等微生物的代谢活动——这表明，随着永久冻土的融化，微生物本身及其副产品可能会被释放到湖泊、河流和海洋中，并有可能进入大气，影响云的形成。然而，以前从未评估过永久冻土是云的种子来源。由于永久冻土覆盖了大约15%的北半球陆地，这种新颖但可能广泛存在的INP源可能对北极云的预测很重要。该项目的首要假设是，从融化的永久冻土中释放的INPs显著影响北极的云特性。这一名为ARCSPIN（北极永久冻土冰核研究）的实地部署包括在阿拉斯加北坡的两个nsf支持的设施中收集和测量永久冻土、湖水、河水和气溶胶中的INPs。此外，本研究利用现有的NSF船载机会从白令海和楚科奇海为INPs收集气溶胶和海水样本。陆基测量提供了对多年冻土INP来源的详细评估，而船载测量则阐明了此类INP的空间范围。研究人员使用气候和地球系统模型将陆地和海洋环境的观测结果联系在一起，并评估永久冻土INPs形成的云对更广泛的北极地区的阳光和热量的影响。提出的联合观测模拟研究通过跨学科的方法来评估物理、生物和大气气候系统过程之间的相互作用，促进了对北极作为一个耦合系统的理解。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。

In a warmer world, the Arctic is projected to become cloudier and rainier. As the Arctic warms more than twice as fast as the rest of the world, resulting changes in clouds can subsequently affect sea ice extent, permafrost thaw, and regional and global weather. However, the formation and evolution of Arctic clouds remain highly uncertain in part due to a limited understanding of airborne particles known as aerosols that seed clouds, specifically aerosols that form cloud ice crystals. These ice crystals, called ice nucleating particles or INPs, can originate from soil, plants, oceans, lakes, and rivers. In particular, the sources and abundance of INPs from Earth’s biome are poorly understood yet may be crucial for cloud ice formation. Warmer temperatures are also triggering rapid and extensive permafrost thaw at high latitudes, which has implications for communities and wildlife living in these regions. Thawing permafrost additionally releases greenhouse gases and promotes metabolic activity in microbes such as bacteria—suggesting the intriguing possibility that as permafrost thaws, the microbes themselves and their byproducts could be released into lakes, rivers, and the ocean, and potentially into the atmosphere to impact cloud formation. However, permafrost has not been previously evaluated as a source of seeds for clouds. Because permafrost covers approximately 15% of Northern Hemisphere land, this novel but potentially widespread INP source may be important for predictions of Arctic clouds.The overarching hypothesis of this project is that INPs released from thawing permafrost significantly influence cloud properties in the Arctic. The field deployment called ARCSPIN (ARCtic Study of Permafrost Ice Nucleation) involves collection and measurement of INPs in permafrost soil, lake water, river water, and aerosols at two NSF-supported facilities on the North Slope of Alaska. Additionally, this study leverages existing NSF shipborne opportunities to collect aerosol and seawater samples from the Bering and Chukchi Seas for INPs. Land-based measurements provide a detailed assessment of permafrost INP sources, while the shipborne measurements clarify the spatial reach of such INPs. The researchers use climate and earth system models to tie together observations in terrestrial and marine environments, and to assess the effects of clouds formed by permafrost INPs on sunlight and heat in the broader Arctic region. The proposed joint observational-modeling study advances the understanding of the Arctic as a coupled system through an interdisciplinary approach to assess interactions among physical, biological, and atmospheric climate system processes.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.