Collaborative Research: Changes in Lake Dynamics on the Arctic Coastal Plain of North America Over the Past Half-Century

北美北极沿岸平原(ACP)约有一半被融化的湖泊和湖泊排干时形成的盆地覆盖，使这些特征成为主导的景观元素和北极系统的重要组成部分。湖泊的形成显然是在温暖的全新世早期开始的，最近来自西西伯利亚和北美持续多年冻土带的证据表明，融化的湖泊正在经历快速变化，以响应气温的上升和直接的人为扰动。到目前为止，我们对导致解冻湖泊形成、扩张和排水的过程的了解有限。大多数基于过程的水文和水动力学研究是在半个世纪前对平坦、年轻的外(海)沿海平原上发育的湖泊进行的。这一地区只占ACP的三分之一，具有与更广泛的内海平原根本不同的地貌特征。此外，对湖泊覆盖率、排水和形态测量(大小和形状)的时空分析在很大程度上局限于自1970年代中期卫星图像首次出现以来的时期。该项目将系统地收集和综合有关融化湖泊变化的信息，以了解影响景观对气候改善作出反应的基本地貌过程。将利用现有的卫星图像对整个机场核心计划进行区域评估，以探测卫星时代湖泊覆盖率和地貌测量的变化。该小组还将使用数字航空照片将分析追溯到1950年左右，对ACP的十个亚区进行分析，并评估变化的时间模式。这些数据将由现有的空间数据集补充，包括地面冰含量、地表沉积物、植被和高分辨率数字高程模型，这些数据用于地理信息系统建模环境，以确定湖泊是否以空间一致的方式对气候变暖做出反应。夏季实地调查将加强这些分析，重点是三个研究区的湖泊蒸发和海岸线侵蚀。该测量计划旨在绘制海岸线变化模式，监测湖泊水位的年际变化，并估计湖泊与大气之间的能量和水分交换。这项研究的四个科学目标和方法是：(1)使用20世纪70年代中期和2000年后的准确联合登记的ACP马赛克，识别和绘制在这段时间内扩大、收缩或排干的湖泊，以评估区域对观测到的变暖的反应；(2)使用约1950年的航空照片的数字版本，分析自1950年以来ACP的十个亚区的湖泊形态和覆盖范围的变化；(3)在横跨机场核心计划的沿海到内陆样带的三个研究区，深入开展湖泊能量和水分收支、蒸发和海岸线侵蚀方面的研究，以复制和扩大50年前国际地球物理年期间进行的类似研究；以及(4)综合现有的各种数字数据源，包括地面冰含量图、表层沉积物、植被和数字高程数据，建立湖泊变化对当地景观特征影响的因果模型。

About half of the Arctic Coastal Plain (ACP) of North America is covered with thaw lakes and the basins that form when lakes drain, making these features the dominant landscape elements and a crucial component of the Arctic system. Lake formation was apparently initiated during the warmer early Holocene, and recent evidence from the continuous permafrost zone of Western Siberia and North America suggests that thaw lakes are experiencing rapid changes in response to increasing air temperature and direct human-induced perturbations.To date, our understanding of the processes leading to thaw-lake formation, expansion, and drainage on the ACP is limited. Most process-based hydrologic and hydrodynamic studies were conducted half a century ago on lakes developed on the flat, young Outer (seaward) Coastal Plain. This region comprises only 1/3 of the ACP, and has geomorphic characteristics fundamentally different from the more extensive Inner Coastal Plain. In addition, spatial and temporal analysis of lake coverage, drainage, and morphometry (size and shape) has been largely restricted to the period since the mid-1970s when satellite images first became available. This project will make a systematic effort to collect and synthesize information on thaw-lake changes to understand the basic geomorphic processes influencing a landscape responding to climatic amelioration.A regional assessment across the ACP will be conducted using existing satellite images to detect changes in lake coverage and morphometry during the satellite era. The group will also use digital aerial photographs to extend the analysis back to ~1950 for ten subregions of the ACP, and assess temporal patterns of change. These data will be supplemented by existing spatial data sets including ground ice content, surficial sediments, vegetation and high resolution digital elevation models, which are used in a Geographic Information System modeling environment to determine if lakes are responding to warming climate in a spatially consistent manner. These analyses will be augmented by summer field studies focused on lake evaporation and shoreline erosion in three study areas. The measurement program is designed to map patterns of shoreline changes, monitor interannual variations in lake levels, and estimate energy and moisture exchange between lakes and the atmosphere.The four scientific goals and the methods that address the intellectual merits of the research are: (1) using an accurate co-registered ACP mosaic of satellite scenes from the mid-1970s and post 2000, identify and map lakes that have enlarged, contracted, or drained over the period to assess regional response to observed warming; (2) using digital versions of circa 1950 aerial photographs, analyze changes in lake morphology and coverage for the period since 1950 for ten subregions of the ACP; (3) in three study areas on a coastal-to-inland transect across the ACP, conduct intensive studies of lake energy and water budgets, evaporation, and shoreline erosion to replicate and expand on similar studies conducted during the International Geophysical Year fifty years ago; and (4) synthesize a variety of existing digital data sources including maps of ground ice content, surficial sediments, vegetation, and digital elevation data to develop causative models relating susceptibility of lake change to local landscape characteristics.