Evidences of Permafrost Signatures in the Planform Shape of Arctic Meandering Streams

Abstract

We investigate whether geomorphic signatures of permafrost are embedded in planforms of river meanders, and we inquire as to how physical factors unique to permafrost environments are able to affect their dynamics. By exploiting satellite imagery, a data set of 19 freely-meandering Arctic rivers is compared against an independent data set of 23 freely-meandering streams flowing through temperate and tropical regions. Suitable dimensionless metrics are defined to characterize morphometric properties of meanders in terms of the spatio-temporal distribution of curvature and channel width. Results show the absence of marked contrasts in the amplitude of bend-curvature between the two data set. Differently, we find a permafrost signature in the channel width response, which manifests itself through larger values of the average bend-width and by peaks of width fluctuations. Field data suggest that permafrost meanders tend to widen for increasing bend sinuosity, likely promoting a shift of their morphodynamic regime as final cutoff is approached.