TO MEASURE THE CHANGING RELIEF OF ARCTIC RIVERS: A SYNTHETIC APERTURE RADAR EXPERIMENT IN ALASKA

The rivers crossing the lowland tundra-permafrost of the continuous permafrost zone of the Alaska North Slope can have extensive floodplain relief not simply created by channel migration during spring floods alone. Many of the rivers have channel-beds inherited from glacial landscapes and Holocene to present-day para-glacial and periglacial processes and mountain gradient sources. Interest is turning to understand effects from permafrost and ice wedge networks (ground ice) thaw, degradation and erosion and how such effects impact carbon and water equivalent mass balance. The 2015 flooding of the Sagavanirktok River crossing the Alaska North Slope brings this and additional impacts to-and-by human infrastructure into focus. Geodetic methods to measure centimeter to millimeter-scale changes using aircraft and satellite-deployed Synthetic Aperture Radio Detection And Ranging cannot ignore volume scattering. Backscatter and coherence at L-frequency and others possess both surface and volumetric scattering. On lowland tundra underlain by permafrost volume scattering dominants the RADAR backscatter coherence. Measurement of the L-frequency penetration depth for evaluation of mass change (carbon and water equivalent loss and transport) through permafrost and ground ice thaw-degradation with erosion is necessary. The Jet Propulsion Laboratory-National Aeronautical and Space Administration airborne Uninhabited Aerial Vehicle SAR (UAVSAR) L-frequency full quad-polarimetry cross-pole HHVV (polarization rotation, Horizontal to Vertical) confirms the dominance of volume scattering on lowland tundra (RADAR-soft targets) whereas surface scattering (HHHH or VVVV, no rotation) dominates on river channel deposits, rock outcrops and metal objects (RADAR-hard targets). Quantifying polarization rotation and the L-frequency penetration depth on lowland tundra are challenges for a new field validation and verification experiment: To Measure The Changing Relief of Arctic Rivers.

Acknowledgements: NASA ABoVE Grant NNX17AC57A, NASA/JPL-Caltech thanked for UAVSAR Data.