Increasing non‐linearity of the storage‐discharge relationship in <scp>sub‐Arctic</scp> catchments
Alexa Hinzman, Ylva Sjöberg, Steve W. Lyon, Stefan Ploum, Ype van der Velde
Abstract
Abstract The Arctic is warming at an unprecedented rate. We hypothesis that as seasonally frozen soils thaw and recede in extent as a response to this warming, flow path diversity and thus hydrologic connectivity increases. This enhanced hydrologic connectivity then increases the non‐linearity of the storage‐discharge relationship in a catchment. The objective of this study is to test this hypothesis by quantifying trends and spatio‐temporal differences in the degree of linearity in the storage‐discharge relationships for 16 catchments within Northern Sweden from 1950 to 2018. We demonstrate a clear increase in non‐linearity of the storage‐discharge relationship over time for all catchments with 75% showing a statistically significant increase in non‐linearity. Spring has significantly more linear storage‐discharge relationships than summer for most catchments (75%) supporting the idea that seasonally frozen soils with a low degree of hydrological connectivity have a linear storage‐discharge relationship. For the period considered, spring also showed greater change in storage‐discharge relationship trends than summer signifying that changes in recessions are primarily occurring during the thawing period. Separate storage‐discharge analyses combined with preceding winter conditions demonstrated that especially cold winters with little snow yielded springs and summers with more linear storage‐discharge relationships. We show that streamflow recession analysis reflects ongoing hydrological change of an arctic landscape as well as offering new metrics for tracking change across arctic and sub‐arctic landscapes.