COLLABORATIVE RESEARCH: Patterns, Dynamics, and Vulnerability of Arctic Polygonal Ecosystems: From Ice-Wedge Polygon to Pan-Arctic Landscapes

随着数千年前的地面冰融化，变暖的北极正在重塑冻土地带的景观，导致不同的地面沉降，改变了沙漠般的降水地区的水和雪的分布。北极各地的实地测量记录了永久冻土的长期和逐渐变暖，最近的观测还包括对一个异常温暖的夏季的快速冰楔退化。该项目的目标是通过结合来自加拿大、俄罗斯和阿拉斯加的9个野外站点的现场测量、数值模拟和最近可用于整个北极冻土带领域的非常高空间分辨率的光学图像，了解导致泛北极冰楔多边形冻土带地貌演变的复杂和相互关联的过程。详细的图像和先进的处理算法相结合，将允许泛北极绘制冰楔多边形范围和类型(低中心和高中心)的地图。这一范围和细节的地图尚未存在，但对于将发生在冰楔多边形尺度上的碳、水和能量过程与更大的北极陆地-海洋-大气系统联系起来是必要的。目前，全球模型充其量只能通过活动层厚度的逐渐增加来描述永久冻土融化和随后的碳释放，而现场观察清楚地表明，由于冰楔融化导致地面快速差异下沉，冻土带生态系统发生了额外的戏剧性变化。几千年来，通过缓慢的冰楔生长过程，低中心的多边形景观演变而来，整个夏天可以容纳一片浅水池的海洋，在繁殖季节为无数候鸟提供支持。在短短两年内，情况可能会发生戏剧性的变化，露出浅水水体曾经所在的干燥土丘，而地表水域面积可能会缩小为融化的冰楔上方更深的池塘组成的细长狭窄的珠子。一组复杂的从多边形到分水岭尺度的响应将决定景观的命运。这些机制是土壤-植被-水连续体的一部分，将通过一个数字生物地球物理模型来定义，该模型由现场测量和重复拍摄的冰楔演化图像提供信息。新的知识将支持研究界完善北极在全球气候系统中的作用。该项目的更广泛影响包括通过支持一名研究生、一名博士后研究员和一名职业生涯早期的科学家来培训新一代北极研究人员。阿拉斯加州的费尔班克斯是几名研究人员的基地，这里提供了一个绝佳的机会，向K-12年级的学生展示冰楔退化的结果。这些产品，如冰楔多边形类型地图和植被、水和地形的投影变换，都是与管理者相关的空间和时间尺度。在为期半天的研讨会上，将向在阿拉斯加运作的州和联邦机构提供冰楔多边形类型和地面冰估计的数字地图，以及冰楔多边形生态系统预测。这些信息可以为有关栖息地保护或依赖地表水的石油和天然气勘探活动的管理决策提供信息。还将支助一名记者和一名摄影师的实地旅行。

The warming Arctic is reshaping the tundra landscape as ground-ice that is thousands of years old thaws, resulting in differential ground settlement that alters the distribution of water and snow in a region with desert-like precipitation. Field measurements across the Arctic have documented long-term and gradual warming of permafrost and recently the observations have also included rapid ice-wedge degradation in response to a single and unusually warm summer. The goal of this project is to understand the complex and interlinked processes responsible for the evolution of the pan-Arctic ice-wedge polygon tundra landscape by combining field measurements from nine Canadian, Russian, and Alaskan field sites, numerical modeling, and very high spatial resolution optical imagery that has recently become available for the entire Arctic tundra domain. A combination of detailed imagery and advanced processing algorithms will allow pan-Arctic mapping of ice-wedge polygon extent and types (low- and high-centered). A map of that extent and detail does not yet exisxt, but is necessary to link carbon, water, and energy processes occurring at the ice-wedge polygon scale to the larger Arctic land-ocean-atmosphere system. Currently, permafrost thaw and subsequent carbon release is, at best, described in global models via gradual increases in active layer thickness, while field observations clearly show additional dramatic changes to the tundra ecosystem due to rapid differential ground subsidence as ice-wedges melt. A low-centered polygon landscape, which evolved over several thousand years via the slow process of ice-wedge growth, can harbor a sea of shallow ponds throughout the summer that supports a myriad of migratory birds during the breeding season. In just two years, the scene could change dramatically with exposed dry mounds where the shallow water bodies once were, while the surface water area can shrink into narrow elongated beads of deeper ponds above the melted ice-wedges. A complicated set of sub-polygon to watershed scale responses will determine the fate of the landscape. These mechanisms, part of the soil-vegetation-water continuum, will be defined via a numerical biogeophysical model informed by field measurements and repeat imagery of ice-wedge evolution. The new knowledge will support the research community in refining the role of the Arctic in the global climate system. Broader impacts of this project include training of the new generation of Arctic researchers by supporting a graduate student, a post-doctoral fellow, and an early-career scientist. Fairbanks, Alaska, the base for several of the investigators, offers an excellent opportunity to show K-12 students the results of ice-wedge degradation. The products, such as the maps of ice-wedge polygon types and the projected transformation of the vegetation, water, and topography, are at spatial and temporal scales that are relevant to managers. Digital maps of ice-wedge polygon type and ground-ice estimates will be given to state and federal agencies operating in Alaska in a half-day workshop along with ice-wedge polygon ecosystem projections. The information could inform management decisions about habitat protection, or surface-water dependent oil and gas exploration activities. There will also be support for field travel for a journalist and a photographer.