Collaborative Research: Arctic Oases - How does the delayed release of winter discharge from aufeis affect the ecosystem structure and function of rivers?

合作研究：北极绿洲 - 冬季排放的延迟释放如何影响河流的生态系统结构和功能？

• 批准号: 1504453
• 负责人: Michael Gooseff
• 金额: $ 7.45万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-15 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1504453&HistoricalAwards=false
• 关键词: Collaborative; Research; Arctic; Oases; How

This is a preliminary study to assess the potential effects of aufeis on the structure and function of arctic river-floodplain ecosystems. Aufeis are massive accumulations of ice common to many arctic rivers, particularly in northeastern Siberia and the North Slope of Alaska. River aufeis form during freeze-up when thickening surface ice and permafrost restrict river discharge, causing water to overflow existing ice. Successive cycles of overflowing and freezing of water from upstream groundwater sources accumulate enormous quantities of ice, with late-winter aufeis on some rivers attaining thicknesses of 3 to 5 meters, covering up to 20 square kilometers in some Alaskan fields (even larger in Siberia), and storing as much as a third of the annual discharge of the river in the form of ice. In addition, aufeis maintain an unfrozen base throughout winter due to the release of latent heat as water is converted to ice, which warms the underlying sediments, and a thick insulating layer of ice above. Although aufeis have been studied by hydrologists and are known to be required for winter and spawning habitat for important local fish species, understanding of their ecology is poor. In recognition of this, these investigators will conduct a targeted assessment of the ecological importance of a single aufeis field on the Kuparuk River, Alaska as a first step toward developing a hypothesis-driven research program. The investigators propose that aufeis be viewed as winter oases due to their wet bases that supply water and heat to otherwise frozen habitats. Aufeis also function as summer oases by providing a stable supply of water to riverbed and downstream habitats. This preliminary study will focus on assessing 1) river flow and nutrient chemistry above, within, and below the aufeis field, and 2) the potential for year-round, unfrozen habitat beneath the aufeis field. The investigators will collect water samples for nutrient analysis in transects extending 2.5 km upstream and downstream from the aufeis field. They will collect hourly data on river stage, temperature, and electrical conductivity along each transect. They will also install pairs of piezometers to depths of 1 meter and 2 meters to measure the vertical hydraulic gradient between the underlying aquifer and the surface channel, and dissolved oxygen, temperature, and electrical conductivity of hyporheic waters at these points. Measurements of vertical hydraulic gradient will determine whether river reaches are generally upwelling or downwelling. To estimate volume and the potential seasonal contributions of the aufeis to river discharge they will use precise digital elevation models created from low-altitude vertical photogrammetry. Year-round temperature and electrical conductivity records will provide data for simple end-member mixing analyses to determine the proportion of aufeis meltwater to the river during the thaw season. During freeze-up and into the winter, these records will provide estimates of potential downstream influences of the spring-water downstream of the aufeis if subsurface flow is maintained. In order to assess the vertical influence of aufeis, the investigators will instrument nine transects with digital temperature loggers. They anticipate that loggers directly under the aufeis will never record temperatures below freezing but that those outside the aufeis footprint will. The investigators also propose August and April ground-penetrating radar surveys to determine thaw depths. Finally, PVC wells penetrating about one meter below the surface will be used to sample small invertebrate animals living in river sediments and below aufeis. The project will support two masters-level graduate students and will involve two undergraduate field assistants in the summer fieldwork.

这是一项初步研究，旨在评估Aufeis对北极河流盆地生态系统结构和功能的潜在影响。 Aufeis是许多北极河流共有的大量冰，尤其是在西伯利亚东北部和阿拉斯加北坡。当增厚的表面冰和永久冻土限制河流排放时，在冷冻过程中形成了Aufeis河，导致水溢出现有的冰。从上游地下水中溢出和冻结水的连续循环积累了大量的冰，在某些河流上，冬季冬季的Aufeis的厚度为3至5米，在阿拉斯加一些田地（Siberia中甚至更大）的厚度为20平方公里，并在冰上存放了一年的冰上。此外，由于水被转化为冰，Aufeis在整个冬季都保持了未脱落的基础，这会加热下面的沉积物，并在上面的冰层冰层厚实的冰层。尽管水文学家已经对Aufeis进行了研究，并且众所周知，冬季和产卵栖息地需要重要的局部鱼类，但对其生态学的了解很差。为了认识到这一点，这些研究者将对阿拉斯加库帕鲁克河上一个Aufeis领域的生态重要性进行有针对性的评估，这是制定假设驱动的研究计划的第一步。调查人员建议将Aufeis视为冬季，因为它们的湿底部为水和热量提供了冷冻栖息地。 Aufeis还通过为河床和下游栖息地提供稳定的水供应作为夏季绿洲。这项初步研究将侧重于评估1）上方，内部和下方的河流流量和营养化学，以及2）在Aufeis领域下方的全年，未腐蚀的栖息地的潜力。研究人员将收集水样以进行养分分析，以延伸到Aufeis场的上游和下游2.5公里和下游。他们将在沿每个样带的河流，温度和电导率上收集每小时数据。他们还将安装成对的压电仪到1米和2米的深度，以测量下面的含水层和表面通道之间的垂直液压梯度，以及在这些点处溶解的氧气，温度和低血压水的电导率。垂直液压梯度的测量将决定河流范围通常是上升流还是下降。为了估算AUFEIS对河流排放的潜在季节性贡献，他们将使用由低空垂直摄影​​测量产生的精确数字高程模型。全年的温度和电导率记录将为简单的最终成员混合分析提供数据，以确定融化季节中Aufeis融化的比例。在冻结和冬季期间，如果保持地下流量保持地下流量，这些记录将估计Aufeis春水的潜在下游影响。为了评估AUFEI的垂直影响，研究人员将使用数字温度登录器来仪器9个样本。他们预计，直接在Aufeis下的伐木者将永远不会记录低于冰点以下的温度，但是Aufeis足迹以外的人会记录。调查人员还提出了8月和4月的地面雷达调查，以确定融化深度。最后，穿透表面以下约一米的PVC井将用于采样生活在河流沉积物中和Aufeis下方的小型无脊椎动物动物。该项目将支持两名硕士级研究生，并将在夏季实地考察中涉及两名本科野外助手。