Characterization of Climatic Influences on Modern Sedimentation in an Arctic Lake, Svalbard, Norway, 2005

Modern sedimentation in Lake Linné was studied as part of the NSF-funded Svalbard REU Project to calibrate the lamination stratigraphy in the glacier-fed lake. Lake Linné, located on the west coast of Spitsbergen, receives melt water from the Linné glacier, located 8 km up valley. The focus of the investigation is to better understand climatic effects on yearly sedimentation, and to better characterize annual variation in the sediment record. Sediment traps were deployed at five sites (each site having traps at varying depths), from July 2003 to August 2004, in order to facilitate spatial and temporal understanding of sedimentation occurring in the lake. The collected sediment was sub-sampled and analyzed using a Coulter LS230 Particle Analyzer in order to characterize textural changes both temporally in each trap, as well as spatially throughout the lake. Sedimentation rates calculated from the recovered yearlong sediment traps ranged from 277 to 28 mg/cm2/yr (1.5 to 0.15 mm/yr) from the most proximal to distal sites respectively. These sedimentation rates compare well to calculated average rates of sedimentation based on thickness of lacustrine sediment in the lake. Changes in grain size recorded in the sediment traps throughout the year demonstrate a strong peak in grain size associated with a spring melt event. These melt-out deposits are substantially coarser (median grain size = 53 µm) than any other sediment deposited during the year, including deposits associated with a high precipitation and discharge event (median grain size < 16 µm). This suggests that the spring melt sediment is deposited by different mechanism, most likely overland flow during the spring melt. Weather events (rain and solar insolation) affected the grain size of sediment deposited proximally in the lake; median grain size is strongly correlated to discharge from the inlet stream in the late summer.

本研究作为美国国家科学基金会（National Science Foundation，NSF）资助的斯瓦尔巴德本科生科研体验计划（Research Experiences for Undergraduates，REU）项目（Svalbard REU Project）的一部分，针对林内湖（Lake Linné）的现代沉积过程展开研究，旨在校准该冰川补给湖的纹层地层序列。林内湖位于斯匹次卑尔根岛（Spitsbergen）西海岸，承接来自上游8公里处林内冰川（Linné Glacier）的融水。本调查的核心目标为：厘清气候对年际沉积作用的影响机制，并精准刻画沉积记录中的年际变化特征。2003年7月至2004年8月期间，研究团队在5个采样点布设了沉积物捕集器（各采样点均设置不同深度的捕集装置），以系统解析该湖沉积作用的时空分布规律。采集所得的沉积物经分样后，采用库尔特LS230颗粒分析仪（Coulter LS230 Particle Analyzer）开展测试分析，从而刻画各捕集器内沉积物的时间尺度粒度变化，以及全湖范围内的空间尺度粒度差异。基于全年回收的沉积物捕集器数据计算得到的沉积速率，在最靠近入水口的近端采样点至最远的远端采样点间依次为277至28 mg/cm²/年（对应1.5至0.15 mm/年）。该沉积速率与基于该湖湖相沉积物（lacustrine sediment）厚度计算得到的平均沉积速率具有良好的一致性。全年沉积物捕集器记录的粒度变化显示，春季融冰事件对应着显著的粒度峰值。相较于年内其他所有沉积产物（包括强降水与高径流量事件对应的沉积物，其中值粒径小于16 µm），融冰沉积的粒径显著更粗，其粒度中值为53 µm。这表明春季融冰沉积物的沉积机制存在显著差异，其主要沉积方式应为春季融冰期间的坡面径流搬运沉积。天气事件（降雨与太阳辐射）会影响湖岸近端沉积的粒度特征；夏末阶段，粒度中值与入水口径流量呈现显著的正相关关系。