Will climate change affect hyporheic processes in arctic streams? An assessment of interactions among geomorphology, hydrology, and biogeochemistry in Arctic stream networks

鲍登OPP-032740这是佛蒙特州大学、博伊西州立大学和犹他州州立大学的首席研究人员共同提出的建议。该项目的目标是评估开放航道周围土壤和沉积物融化区域(即解冻球茎)的地貌和季节变化如何控制北极河流浅水区的水力和生物地球化学动态。其前提是：a)河流地貌设定了一个物理模板，控制着北极河流周围亚流活动层(或解冻球)的季节性发展；b)解冻球的范围控制着潜流带的发育潜力；c)潜流带对河流中的碳(C)、氮(N)和磷(P)的处理有很大贡献。首席调查人员预计，北极气候变化有可能通过直接影响降水、径流、年平均温度和融化季节持续时间，以及间接影响河流地貌，显著改变融化球和潮汐动力学。为了解决这一中心假设，他们提出了四个目标：1.选择和描述代表北坡河流地貌条件范围的河流河段。2.在每个河段的几个河流横断面上，利用探地雷达和地下温度测量，监测整个解冻季节的支流融化球大小。3.在每个河段的融化季节进行反复的潜水交换研究(水系溶质添加试验)，以确定水深水力特性。4.在每个河段的融化季节，重复测量营养盐(N和P)的浓度和周转时间，以确定生物地球化学特征。这些目标将通过现场监测(热敏电阻阵列、湿法采样)、现场实验(溶质添加)和建模(地下水传输和瞬时储存)工作相结合来实现。这项研究很重要，因为目前还没有关于北极系统中潜流带结构和功能的文献报道。温带地区的大量研究表明，高潮区是河流生态系统的重要组成部分。河流初级生产量的很大一部分可能由淡水过程中再生的营养物质支持。这种再生依赖于有机物质的输入(包括原地和异地)。因此，潮汐处理对于理解溪流如何改变跨景观的碳、氮和磷的运输也很重要。将北极河流的这些重要功能量化的研究是不存在的。更广泛的影响：对这一主题的研究对于我们理解北极河流的生态功能是重要的。鉴于河流是连接陆地和海洋的管道，那么河流中影响物质运输的过程对于理解陆地径流如何影响海洋肯定很重要。此外，如果气候变化影响流中加工的速度或程度，那么可能会对材料从陆地到海洋的运输产生重要影响，这项研究将开始解决这一问题。因此，这些研究对于提供数据和知识至关重要，这些数据和知识将对其他科学家、政策制定者、资源管理人员以及最终对社区利益攸关方有用。

ABSTRACTBowdenOPP-032740 This is a collaborative proposal by Principal Investigators at the University of Vermont, Boise State University and Utah State University. The goal of this project is to assess how geomorphology and seasonal changes in the thawed region of soil and sediment around the open channel (i.e.; the thaw bulb) control hydraulic and biogeochemical dynamics in the hyporheic zone of Arctic streams. The premise is that: a) stream geomorphology sets a physical template that controls the seasonal development of the sub-stream active layer (or thaw bulb) around Arctic streams; b) the thaw bulb extent controls the potential for development of the hyporheic zone, and c) the hyporheic zone substantially contributes to carbon (C), nitrogen (N) and phosphorous (P) processing in streams. The Principal Investigators anticipate that climate change in the Arctic has the potential to significantly alter the thaw bulb and hyporheic dynamics through its influences directly on precipitation, runoff, average annual temperature, and thaw season duration, and indirectly on stream geomorphology. To address this central hypothesis, they propose four objectives: 1. Select and characterize stream reaches that represent the range of geomorphologic conditions in rivers of the North Slope. 2. Monitor the sub-stream thaw bulb size through the thaw season using ground penetrating radar and subsurface temperature measurement in several stream cross-sections within each reach. 3. Conduct repeated hyporheic exchange studies (stream solute addition experiments) through the thaw season in each reach to determine hyporheic hydraulic characteristics. 4. Conduct repeated measures of nutrient (N and P) concentrations and turnover time in the hyporheic zone through the thaw season in each reach to determine biogeochemical characteristics. These objectives will be addressed through a combination of field monitoring (thermistor arrays, hyporheic sampling), field experiments (solute additions), and modeling (groundwater transport and transient storage) efforts. This research is important because there is no reported literature on the structure and functions of the hyporheic zone in Arctic systems. Considerable research in temperate regions suggests that hyporheic zones are critical components of stream ecosystems. A significant portion of the primary production in streams may be supported by nutrients regenerated from hyporheic processes. This regeneration is dependent on organic matter inputs (both autochthonous and allochthonous). Thus, hyporheic processing is also important in understanding how streams modify carbon, nitrogen, and phosphorous transport across landscapes. Research which quantifies these important functions in Arctic streams is non-existent.Broader Impacts: Research on this subject is important as a direct input to our understanding of the ecological functions of Arctic streams. Given that rivers are the conduits that link land to the ocean, then processes within streams that modify material transport must be important to understanding how runoff from land affects oceans. Furthermore, if climate change affects the rate or extent of in-stream processing, then there may be important impacts on the transport of materials from land to the ocean, which this research would begin to address. Therefore, these studies are essential to provide data and knowledge that will be of use to other scientists, policy makers, resources managers, and ultimately to community stakeholders.