NNA: LTREB: The Arctic Carbon and Climate (ACCLIMATE) Observatory: Tundra Ecosystem Carbon Balance and Old Carbon Loss as a Consequence of Permafrost Degradation

地球大气层的未来轨迹取决于陆地和海洋对不断变化的环境的反应，特别是北极等高纬度地区大量持续碳释放的潜力。理解地球系统将如何应对的一个关键问题是，是否存在临界点--全球碳循环的意外--这将使海平面上升、极端天气、干旱和对农业的影响等环境变化的影响比目前模型预测的更快。永久冻土碳，植物，微生物和动物的残余物在北极常年冻土中积累了数千年，目前的碳含量是大气的两倍，可能是这样一个临界点。只要将这些冻结的碳中的一小部分以二氧化碳和甲烷的形式释放到大气中，就会大大增加未来全球环境变化的速度。从永久冻土地区释放到大气中的每一吨碳都会给社会带来额外的成本，并带来了需要持续长期观测的挑战，以量化速率并揭示机制，以便预测变化。该项目将建立北极碳和气候（ACCLIMATE）永久冻土碳观测站，该观测站将利用实地观测来测量碳通量，以及由于区域变暖而正在经历快速和不可逆转变化的苔原生态系统中的生态系统碳库。北极碳与气候（ACCLIMATE）永久冻土碳观测站利用实地观测，测量冻土带生态系统中的碳通量、碳同位素比率和生态系统碳库，冻土带生态系统正因区域变暖而发生快速且不可逆转的变化。阿拉斯加内陆八里湖研究流域的多年冻土温度在20世纪90年代初多年冻土退化开始之前已经监测了几十年。多年冻土退化对植物、微生物和生态系统碳平衡的影响在21世纪初开始被记录。总体研究计划将回答三个焦点问题：1）变暖和永久冻土退化是否会导致生态系统向大气中净释放碳，以及其数量在几年到几十年内如何变化？2)这种碳释放中有多大比例来自于构成土壤碳库大部分的旧碳，随着解冻的进行，这一比例会增加吗？3)地表水文的变化如何与融化相互作用，以控制旧的碳损失和二氧化碳和甲烷的分配？碳测量沿着该观测站收集的其他关键生态系统变量将被组织起来，用于对区域和地球系统模型进行基准测试，并通过持续的综合和模型相互比较活动与该过程相结合。这些技术活动将与知识转移活动相结合，将成果与更广泛的科学界以及更广泛的公众联系起来。该奖项反映了NSF的法定使命，并被认为值得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来支持。

The future trajectory of Earth's atmosphere depends on the response of land and ocean to a changing environment, especially the potential for substantial sustained carbon release in high latitude regions like the Arctic. A key question in understanding how the Earth system will respond is whether there are tipping points - global carbon cycle surprises - that will make the effects of environmental change such as sea-level rise, extreme weather, droughts, and impacts on agriculture occur faster than currently projected by models. Permafrost carbon, the remnants of plants, microbes, and animals accumulated in perennially frozen Arctic soil over thousands of years, currently holds twice as much carbon as the atmosphere, and could be such a tipping point. Release of just a fraction of this frozen carbon as carbon dioxide and methane into the atmosphere would significantly increase the rate of future global environmental change. Each additional ton of carbon released from the permafrost region to the atmosphere incurs additional costs to society and presents the challenge of requiring sustained long-term observations to quantify rates and unravel mechanisms in order to forecast change. This project will establish the Arctic Carbon and Climate (ACCLIMATE) permafrost carbon observatory, which will use field observations to measure carbon fluxes, and ecosystem carbon pools in a tundra ecosystem that is undergoing rapid and irreversible change due to regional warming. The project will also include training of a postdoctoral researcher and several undergraduate students, and outreach activities involving high school students and teachers.The Arctic Carbon and Climate (ACCLIMATE) permafrost carbon observatory uses field observations to measure carbon fluxes, carbon isotope ratios, and ecosystem carbon pools in a tundra ecosystem that is undergoing rapid and irreversible change due to regional warming. Permafrost temperature at the Eight Mile Lake research watershed in Interior Alaska has been monitored for several decades starting before permafrost degradation began in the early 1990s. The impact of permafrost degradation on plants, microbes, and ecosystem carbon balance began to be documented in the early 2000s. The overall research plan will answer three focal questions: 1) Does warming and permafrost degradation cause a net release of carbon from the ecosystem to the atmosphere, and how does the magnitude change over years to decades? 2) What proportion of this carbon release is derived from old carbon that comprises the bulk of the soil carbon pool, and will this increase as thaw progresses? 3) How does change in surface hydrology interact with thawing to control old carbon losses and the partitioning of carbon dioxide and methane? Carbon measurements, along with other key ecosystem variables collected by this observatory, will be organized for benchmarking regional and Earth System models, and coupled to that process through ongoing synthesis and model inter-comparison activities. These technical activities will be integrated with knowledge-transfer activities that link results to the broader scientific community, as well as to the broader public.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.