AUFEIS AS A FORCING MECHANISM FOR CHANNEL AVULSION AND IMPLICATIONS OF WARMING CLIMATE

Prompted by field observation of an aufeis-induced channel avulsion along the Hula Hula River in June 2021, we use measurements of channel migration zone width along 15 rivers draining north from the Brooks Range across the Arctic coastal plain in Alaska, USA. These rivers are non-perennial in that they freeze solid during winter, with no flow except from the groundwater springs that create aufeis, or shelf ice along the river corridor. We differentiated sites with aufeis that covered > 1 km² in early summer during the period 2017-2021 from sites without such aufeis formation. All but 4 of the 28 sites with aufeis have widths greater than the 95% confidence interval and 20 sites fall outside of the 95% prediction interval for channel width based on drainage area. Pairwise comparison indicates that the population of aufeis sites have significantly wider channel migration zones (p <0.0001) than non-aufeis sites after accounting for drainage area. Seasonal aufeis facilitates lateral channel migration and associated heterogeneity. Loss of aufeis under warming climate may reduce habitat diversity in these river corridors.