Collaborative Research: Chemical Weathering and Organic Carbon Export from Arctic Watersheds, North Slope, Alaska

合作研究：阿拉斯加北坡北极流域的化学风化和有机碳输出

• 批准号: 0806827
• 负责人: James McClelland
• 金额: $ 26.46万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0806827&HistoricalAwards=false
• 关键词: Collaborative; Research; Chemical; Weathering; Organic

Abstract 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.

摘要最近的气候变化极大地影响了北极，模型表明，随着二氧化碳在大气中的持续积累，将来会发生加速效应。理解这个问题很重要，因为北极环境变化可能会在人类时期内会产生行星尺度的影响。特别是，在多年冻土中存储的有机碳的氧化可能会产生对全球变暖的积极反馈。尽管大量研究集中在北极中的变暖与碳循环之间的关系，但大气二氧化碳水平上升对化学风化过程的具体影响以及有机碳动力学的耦合变化却相对较少。该项目具有两个综合目标：确定矿物风化反应和水文过程，这些反应控制了如何并以何种有机溶质溶质地球化学在土壤和溪流中的运输过程中进化，并在化学风化现象与有机碳出口之间建立联系。这项工作将集中于雷德流的主要离子和同位素地球化学，以及耗尽阿拉斯加北坡的小溪。基于初步数据，工作的指导假设是，碳酸盐与硅酸盐风化的比率响应于排放和多年冻土主动层深度的季节性变化，在基本流动条件下观察到最高比率，最大的活性层深度和最大的比率。在峰值流量条件和最小的活动层深度期间观察到的最低比率。为了检验这一假设及其对了解有机碳出口的影响，该团队将：1）量化主要阳离子释放，二氧化碳消耗和溶解有机碳（DIC）生产的速率，碳酸盐和硅酸盐风化； 2）评估对河流和土壤的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流水成分之间的关​​系，包括水的H和O同位素，有机物浓度以及有机物的同位素组成（C和N）。他们将收集水，沉积物，基岩和土壤样品。水采样将从春季融化到秋季冷冻。在实验室中，他们将进行浸出和消化实验，以量化矿物风化最终成员。他们将使用质量平衡建模，碳酸盐平衡计算，水文分离以及元素和同位素混合方程来合成数据。这项研究是阐明北极阿拉斯加河流的同位素和有机地球化学之间基本联系的第一个综合努力之一。由于变暖可能会改变碳酸盐通过多种反馈机制硅酸盐风化的比率，因此该研究将建立一种新的方法来监测流域量表的北极环境变化。