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

北美大约一半的北极海岸平原（ACP）被融化湖泊和湖泊排水时形成的盆地覆盖，使这些特征成为主要的景观元素和北极系统的关键组成部分。湖的形成显然是在温暖的全新世早期开始的，最近来自西伯利亚西部和北美连续永久冻土带的证据表明，由于气温升高和人类直接引起的扰动，融湖正在经历快速变化。迄今为止，我们对ACP上导致冰湖形成、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研究是在半个世纪前对平坦的、年轻的外（向海）海岸平原上开发的湖泊进行的。该地区仅占ACP的1/3，其地貌特征与更广阔的内海岸平原根本不同。此外，湖泊覆盖、排水和形态（大小和形状）的时空分析主要局限于自20世纪70年代中期卫星图像首次出现以来的时期。本项目将系统地收集和综合有关融冰湖变化的信息，以了解影响景观的基本地貌过程，以响应气候改善。在卫星时代，将利用现有的卫星图像对整个亚太区域进行区域评估，以检测湖泊覆盖和形态测量的变化。该小组还将使用数字航空照片，将对非加太10个分区域的分析时间延长至1950年，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，这些数据集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响应气候变暖。这些分析将通过夏季在三个研究区域集中进行湖泊蒸发和海岸线侵蚀的实地研究而得到加强。该测量计划旨在绘制海岸线变化的模式，监测湖泊水位的年际变化，并估计湖泊和大气之间的能量和水分交换。研究的四个科学目标和方法是：(1)利用20世纪70年代中期和2000年后卫星场景的精确共登记ACP马赛克，识别和绘制在此期间扩大、缩小或枯竭的湖泊，以评估区域对观测到的变暖的响应；(2)利用1950年左右航拍照片的数字版本，分析了ACP 10个次区域1950年以来湖泊形态和覆盖的变化；(3)在横跨ACP的沿海至内陆样带的三个研究区内，对湖泊能量和水收支、蒸发和海岸线侵蚀进行深入研究，以复制和扩展50年前国际地球物理年期间进行的类似研究；(4)综合现有的各种数字数据源，包括地面冰含量图、地表沉积物图、植被图和数字高程数据，建立湖泊变化对当地景观特征敏感性的因果模型。

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.