Multi-decadal year-round CO2 and CH4 fluxes to understand long-term impact of climate change on the Arctic carbon balance

北方土壤中的有机碳是目前大气碳储量的两倍多。越来越多的有机碳很容易转化为二氧化碳(CO2)和甲烷(CH4)。然而，由于北极生态系统的空间和全年数据稀少，北极碳随气候变化的潜在损失率仍然存在很大的不确定性。在过去的30年里，极北纬地区的气温上升了0.6摄氏度，是全球平均水平的两倍，其中非夏季的上升幅度最大。这一增长与高纬度湿地大气中温室气体(GHG)通量浓度的增加有关，但这种新增长的驱动因素在很大程度上仍不确定。如果没有冻土带生态系统的长期记录，就不可能预测大气温室气体浓度的变化或将其归因于北极生态系统碳损失的增加。尤其未知的是北极冷季碳损失的反应，因为夏季以外的数据很少。该项目将生成对确定北极温室气体平衡的时间变化至关重要的长期连续数据，并将试图确定不断变化的冷季气候条件可能如何改变北极温室气体向大气的年度排放。这一知识是为当前和未来的模型提供信息并帮助确保对北极未来温室气体排放的严格预测所必需的。该项目将支持北极地区人数不足的学生继续参与。该项目将在阿拉斯加州乌特恰格维克的当地初中和高中开展推广活动，并将继续与伊利萨格维克学院合作，让当地学生参与研究活动。该项目建立长期、全年的实地观察，以更好地了解在包括气候变化和可变性的时间尺度上控制北极温室气体(GHG)排放的情况。该项目将创建运行时间最长的全年北极涡旋协方差网络，并对该网络进行标准化、升级和应用，以提高对气候变化和变化对北极痕量气体反馈的长期影响的理解。该项目将使现有数据更加有用，并将扩大已经很大的用户基础。特别强调的是秋季零帷幕期，此时未冻结的土层徘徊在0摄氏度左右，支持向大气释放大量二氧化碳和甲烷。零幕过程合理地解释了为什么高地冻土带比低洼潮湿的冻土带排放更多的甲烷，以及为什么寒冷的季节可能比夏天排放更多的甲烷。五个北极涡旋协方差通量塔将被用来评估在乌特恰格维克的三个水分环境和通过阿特卡苏克和伊沃图克的约300公里纬度梯度上CO2和CH4通量的长期变化。这些测量旨在具有足够的持续时间和广度，以捕捉和解释极端和/或意外事件对北极温室气体通量的影响。该项目将允许将时间序列扩展到20多年的二氧化碳记录和11年的CH4通量记录，从而产生一个前所未有的数据集，对于完善我们对北极CH4损失控制的分析和预测能力至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Organic carbon in northern soils is more than double the current atmospheric pool. An increasing fraction of this organic carbon is vulnerable to conversion to carbon dioxide (CO2) and methane (CH4). However, there are still large uncertainties in the potential rates of carbon loss from the Arctic with climate change because of the sparse spatial and year-around data from Arctic ecosystems. Temperatures in far northern latitudes have increased by 0.6 °C in the last 30 years, which is twice the global average with the largest increase in the non-summer seasons. This increase has been linked to increased atmospheric concentration of greenhouse gas (GHG) fluxes in high latitude wetlands but the drivers of this renewed growth are still largely uncertain. It is impossible to predict or attribute changes in atmospheric greenhouse gas concentration to increased carbon loss from Arctic ecosystems without a long-term record from tundra ecosystems. Particularly unknown is the response of cold season carbon loss from the Arctic, given the sparse data available outside of the summer period. This project will generate the long-term continuous data critical to identify temporal changes in GHG balance from the Arctic and will attempt to identify how changing cold season climatic conditions may alter annual Arctic greenhouse gas release to the atmosphere. This knowledge is required to inform current and future models and help ensure rigorous predictions of future GHG emissions from the Arctic. This project will support continued engagement of under-represented students in the Arctic. The project will conduct outreach at the local middle and high schools in Utqiagvik, Alaska, and will continue to collaborate with Ilisagvik College to involve the local students into research activities.This project establishes long-term, year-round field observations to better understand the controls on greenhouse gas (GHG) emissions from the Arctic at time scales that will encompass climate change and variability. This project will allow creating the longest running year-round Arctic eddy covariance network, and to standardize, upgrade, and apply the network to improve understanding of the long-term effects of climate variability and change on trace gas feedbacks from the Arctic. This project will make existing data more useful and will expand an already large user base. A special emphasis will be on the fall zero curtain period when an unfrozen soil layer hovers around 0°C supporting significant CO2 and CH4 releases to the atmosphere. Zero curtain processes plausibly explain how upland tundra can be a larger emitter of CH4 than low-lying, wet tundra, and how the cold seasons might emit more CH4 than the summer. Five Arctic eddy covariance flux towers will be used to evaluate the long-term changes in the CO2 and CH4 fluxes across three moisture environments in Utqiagvik and a ~300km latitudinal gradient passing through Atqasuk and Ivotuk. These measurements are intended to be of sufficient duration and breadth to capture and interpret the effect of extreme and/or unexpected events on GHG fluxes in the Arctic. This project will allow expansion of the time-series to a more than 20-year record of CO2 and 11-year record of CH4 fluxes, resulting in an unprecedented dataset critical to refining our analytical and predictive ability of the controls of CH4 loss from the Arctic.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.