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

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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.