Collaborative Research: Chemical Weathering and Organic Carbon Export From Arctic Watersheds, North Slope, AK

最近的气候变化对北极产生了巨大影响，模型表明，随着二氧化碳继续在大气中积累，未来将出现加速影响。理解这个问题很重要，因为北极的环境变化可能在人类的时间尺度内产生行星级的影响。特别是，永久冻土中储存的有机碳的氧化可能会对全球变暖产生积极的反馈。虽然许多研究都集中在北极变暖与碳循环之间的关系上，但大气中二氧化碳含量上升对化学风化过程的具体影响以及有机碳动态的耦合变化却很少受到关注。确定矿物风化反应和水文过程，控制水的无机溶质地球化学如何以及以何种速率演变在土壤和河流中的运输过程中，并建立化学风化现象和有机碳输出之间的联系。这项工作将集中在主要离子和同位素地球化学的源头溪流和小溪排水的阿拉斯加北坡。根据初步数据，工作的指导假设是，碳酸盐硅酸盐风化的比例波动，在流量和冻土活动层深度的季节性变化，最高的比例在基流条件和最大活动层深度和最低的比例在峰值流量条件和最小活动层深度。为了验证这一假设及其对理解有机碳输出的影响，该团队将：1）量化碳酸盐和硅酸盐风化产生的主要阳离子释放，CO2消耗和溶解有机碳（DIC）的速率; 2）评估河流和土壤的Ca，Sr和C（DIC）同位素组成的控制;（3）建立这些示踪剂与其他河水组分之间的关系，包括水的H和O同位素、有机质浓度和有机质的同位素组成（C和N）。他们将收集水、沉积物、基岩和土壤样本。水取样将从春季解冻到秋季冻结。在实验室中，他们将进行浸出和消化实验，以量化矿物风化端元。他们将综合数据使用质量平衡模型，碳酸盐平衡计算，水文分离，元素和同位素混合equations.This研究代表了第一个综合努力阐明北极阿拉斯加河流的同位素和有机地球化学之间的基本联系。由于气候变暖可能会通过几种反馈机制改变碳酸盐与硅酸盐风化的比例，因此本研究将建立一种在流域尺度上监测北极环境变化的新方法。

Recent climate change has dramatically impacted the Arctic, and models suggest that accelerated effects will occur in the future as CO2 continues to accumulate in the atmosphere. Understanding this problem is important because arctic environmental change could have planetary-scale repercussions within human timescales. In particular, oxidation of organic carbon stored in permafrost might create a positive feedback to global warming. While numerous studies have focused on the relationship between warming and carbon cycling in the Arctic, specific effects of rising atmospheric CO2 levels on chemical weathering processes and coupled changes in organic carbon dynamics have received relatively little attention.This project has two integrated goals: to identify mineral weathering reactions and hydrologic processes that control how and at what rate the inorganic solute geochemistry of water evolves during transport within soils and streams and to establish linkages between chemical weathering phenomena and organic carbon export. The work will focus on the major ion and isotope geochemistry of headwater streams and creeks draining the North Slope of Alaska. Based on preliminary data, the guiding hypothesis of the work is that the ratio of carbonate to silicate weathering fluctuates in response to seasonal changes in discharge and permafrost active layer depth, with the highest ratios observed during base flow conditions and maximum active layer depth and the lowest ratios observed during peak flow conditions and minimum active layer depth. To test this hypothesis and its implications for understanding organic carbon export, the team will: 1) Quantify rates of major cation release, CO2 consumption, and dissolved organic carbon (DIC) production by carbonate and silicate weathering; 2) Evaluate controls on the Ca, Sr, and C (of DIC) isotope composition of rivers and soils; and 3) Establish relationships between these tracers and other river water constituents, including H and O isotopes of water, organic matter concentrations, and the isotope composition of organic matter (both C and N). They will collect water, sediment, bedrock, and soil samples. Water sampling will occur from spring thaw through fall freeze-up. In the laboratory, they will conduct leaching and digestion experiments to quantify mineral weathering end members. They will synthesize data using mass-balance modeling, carbonate equilibria calculations, hydrograph separations, and elemental and isotope mixing equations.This study represents one of the first integrative efforts to elucidate fundamental linkages between the isotope and organic geochemistry of Arctic Alaskan rivers. Because warming will likely alter the ratio of carbonate to silicate weathering via several feedback mechanisms, this study will establish a novel method for monitoring Arctic environmental change at the watershed scale.