Collaborative Research: The role of capillaries in the Arctic hydrologic system

融冰丰富的永久冻土正在把北极冻土带的景观从相对平坦和均匀湿润变成由干燥的土丘和狭窄的池塘组成的马赛克。随着解冻的推进，一个排水良好的景观可能会形成一个由微小的地表排水系统组成的迷宫。这种密集的小通道网络代表了北极水文系统的毛细血管，是大河的水源来源。由于冻土带景观的整体干燥，河流径流的增加，以及更多的营养物质从陆地输出到水生环境，不断扩大的毛细管水文系统可能会改变野生动物的栖息地。此外，从亚米分辨率卫星图像中可以识别的不断扩大的毛细管水文网络可以作为富冰永久冻土融化的指标，因此可以警告基础设施的危害。地表排水系统的发展和扩大也可能减少苔藓茁壮成长的可能性，这导致植被覆盖的丧失，而植被覆盖可以有效地冷却地面并保护上层永久冻土不解冻。该项目将制作一幅毛细管水文系统的泛北极地图，并在选定的地区，促进对毛细管系统如何随时间变化的理解。地理空间产品将在永久冻土发现门户上向公众开放，使科学家、利益相关者和公众能够发现和产生知识。实地观测表明，近几十年来，许多北极河流的径流量有所增加。同时，一些研究记录了整个北极的冰楔退化，阿拉斯加北部的一些当地实地和遥感研究表明，由于冰楔的部分融化，毛细管水文系统正在扩大。该项目旨在绘制整个泛北极苔原的毛细水文系统的范围，并评估毛细系统在产生水流和向大河的横向碳通量方面的作用。应用于泛北极冰楔多边形图的图形分析技术，以及训练用于从高空间分辨率卫星图像中检测毛细管系统的深度学习/人工智能算法，将使整个北极冻土带的冰楔网络和毛细管水文系统得以绘制出来。在阿拉斯加北部和西北部的实地测量将包括地球化学水取样，永冻层取样以评估冰楔状态（退化或稳定），以及遥感水文网络分析的地面真相。这一新信息将为数值水文学模型提供信息，以量化毛细血管在向北冰洋提供淡水和碳流方面的重要性。早期的水文模型实验表明，即使降雨和降雪量保持不变，连接槽网的形成也可以使景观径流增加一倍。水文毛细血管的泛北极地图将支持首次研究亚米宽通道对北极大河流径流的重要性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Thawing ice-rich permafrost is transforming Arctic tundra landscapes from being relatively flat and evenly moist into a mosaic of dry mounds and narrow ponds. As thaw progresses, a well-drained landscape with a maze of tiny surface drainages may form. This dense network of small channels represents the capillaries of the Arctic hydrologic system and serves as the originators of the water that feeds large rivers. An expanding capillary hydrologic system may change habitat for wildlife due to an overall drying of the tundra landscape, increased river runoff, and through more nutrients exported from terrestrial to aquatic environments. Further, an expanding capillary hydrological network that is identifiable from sub-meter resolution satellite imagery can serve as an indicator of ice-rich permafrost thaw and, therefore, warn of hazard to infrastructure. The development and expansion of a surface drainage system may also decrease the likelihood of moss to thrive, which results in loss of a vegetation cover that effectively cools the ground and preserves the upper permafrost from thawing. The project will produce a pan-Arctic map of the capillary hydrological system and in selected areas, advance understanding of how the capillary system has changed over time. The geospatial products will be made publicly accessible on the Permafrost Discovery Gateway to enable discovery and knowledge-generation by scientists, stakeholders, and the public.Field observations have shown that runoff from many Arctic rivers has increased in recent decades. Simultaneously, several studies have documented ice wedge degradation across the Arctic, and a handful of local field and remote sensing studies in Northern Alaska have shown that the capillary hydrologic system is expanding due to partial melting of ice wedges. This project aims to map the extent of the capillary hydrologic system across the pan-Arctic tundra and assess the role of the capillary system in generating water flow and lateral carbon flux to large rivers. Graph analysis techniques applied to the pan-Arctic ice-wedge polygon map, as well as deep learning/AI algorithms trained to detect a capillary system from very high spatial resolution satellite imagery, will allow the network of ice wedges and the capillary hydrologic system to be mapped across the Arctic tundra. Field measurements in northern and northwestern Alaska will include geochemical water sampling, coring of permafrost to assess ice-wedge status (degradation or stabilization), and ground-truthing for the remote sensing hydrologic network analyses. This new information will inform a numerical hydrology model to quantify how important the capillaries are in contributing freshwater and carbon flows to the Arctic Ocean. Earlier hydrological model experiments have shown that the formation of connected troughs-networks can double the runoff from the landscape even if the rain and snowfall amounts remain unchanged. The pan-Arctic map of hydrological capillaries will support a first study on how important sub-meter wide channels are to large Arctic river runoff.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.