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

融化的富含冰的永久冻土层正在将北极冻土带的地形从相对平坦和均匀潮湿转变为由干燥的丘陵和狭窄的池塘组成的马赛克。随着融化的进行，可能会形成排水良好的地貌，以及迷宫般的微小表面排水系统。这个密集的小型水道网络代表着北极水文系统的毛细血管，是流入大河的水的发源地。不断扩大的毛细水文系统可能会改变野生动物的栖息地，这是因为冻土地带的整体干燥，河流径流的增加，以及从陆地环境向水生环境输出更多的营养物质。此外，可以从亚米分辨率卫星图像中识别的不断扩大的毛细水文网络可以作为富含冰的永久冻土融化的指标，因此可以警告对基础设施的危险。地面排水系统的开发和扩展还可能降低苔藓茁壮成长的可能性，这会导致失去有效冷却地面并保护上层永久冻土免受融化的植被覆盖。该项目将绘制一张毛细水文系统的泛北极地图，并在选定的地区促进对毛细系统如何随时间变化的了解。地理空间产品将在永久冻土发现门户上向公众开放，以使科学家、利益相关者和公众能够发现和创造知识。实地观察表明，近几十年来，北极许多河流的径流有所增加。与此同时，几项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，毛细水文系统正在扩大。该项目的目的是绘制横跨泛北极冻土带的毛细水文系统的范围图，并评估毛细系统在产生流向大河的水流和横向碳通量方面的作用。将图形分析技术应用于泛北极冰楔多边形图，以及为从非常高的空间分辨率卫星图像中检测毛细系统而训练的深度学习/人工智能算法，将使冰楔网络和毛细水文系统能够绘制北极冻土带的地图。阿拉斯加北部和西北部的实地测量将包括化探水样、取心永久冻土以评估冰楔状态(退化或稳定)，以及用于遥感水文网络分析的地面真实情况。这一新信息将为一个数字水文学模型提供信息，以量化毛细血管在为北冰洋贡献淡水和碳流方面的重要性。早期的水文模型实验表明，即使降雨量和降雪量保持不变，连通的沟槽网络的形成也可以使地貌的径流量增加一倍。泛北极水文毛细血管地图将支持一项关于亚米宽航道对大型北极河流径流有多重要的首次研究。这项奖励反映了NSF的法定使命，并通过使用基金会的智力优势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.