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

北极变暖正在重塑苔原景观，数千年前的地面冰融化，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。北极地区的实地测量记录了永久冻土的长期逐渐变暖，最近的观测还包括由于一个异常温暖的夏季而导致的冰楔快速退化。该项目的目标是通过结合来自加拿大、俄罗斯和阿拉斯加9个野外地点的实地测量、数值模拟和最近可用于整个北极冻土带区域的高空间分辨率光学图像，了解泛北极冰楔多边形冻土带景观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，将允许对冰楔多边形的范围和类型（低中心和高中心）进行泛北极制图。这种范围和细节的地图目前还不存在，但有必要将冰楔多边形尺度上发生的碳、水和能量过程与更大的北极陆地-海洋-大气系统联系起来。目前，在全球模式中，永久冻土融化和随后的碳释放充其量只能通过活动层厚度的逐渐增加来描述，而实地观测清楚地表明，由于冰楔融化导致的快速差异地面沉降，冻土带生态系统发生了额外的剧烈变化。一个低中心的多边形景观，经过几千年缓慢的冰楔生长过程演变而成，可以在整个夏天庇护一片浅池塘，在繁殖季节为无数的候鸟提供栖息地。在短短两年的时间里，这一景象可能会发生巨大的变化，浅水区曾经是干涸的土丘，而地表水区域可能会缩小成融化的冰楔上方更深的池塘的狭窄细长的珠子。一组复杂的子多边形对流域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，将通过一个由野外测量和冰楔演变的重复图像提供信息的数值生物地球物理模型来定义。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。该项目更广泛的影响包括通过支持一名研究生、一名博士后和一名早期职业科学家来培训新一代北极研究人员。阿拉斯加的费尔班克斯是几位研究人员的基地，这里提供了一个绝佳的机会，向K-12学生展示冰楔退化的结果。这些产品，如冰楔多边形类型的地图和植被、水和地形的预测转换，都是与管理人员相关的空间和时间尺度。在为期半天的研讨会上，冰楔多边形类型和地面冰估计的数字地图将与冰楔多边形生态系统预测一起提供给在阿拉斯加运作的州和联邦机构。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。还将为一名记者和一名摄影师的实地旅行提供支持。

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.