Increasing non-linearity of the storage-discharge relationship during a
period of thawing soils and climate warming in Northern Sweden
Abstract
The Arctic is warming at an unprecedented rate. One relatively under
researched process is how seasonally frozen soils and changes thereof
affect the water cycle. As frozen soils thaw, flow pathways within a
watershed open, allowing for enhanced hydrologic connectivity between
groundwater and rivers. As the connectivity of flow paths increase, the
storage-discharge relationship of a watershed changes. The objective of
this study is to quantify trends and spatio-temporal differences in the
degree of linearity in the storage-discharge relationships for sixteen
watersheds within Northern Sweden throughout the years of 1950 and 2018.
We demonstrate a clear increase in non-linearity of the
storage-discharge relationship over time for all catchments with twelve
out of sixteen watersheds (75%) having a statistically significant
increase in non-linearity. Springs have significantly more linear
storage-discharge relationships than summer for twelve watersheds
(75%), which supports the idea that seasonally frozen soil with a low
degree of hydrological connectivity have a linear storage-discharge
relationship. For the period considered, spring showed the greater
change in storage-discharge relationship trends than summer, signifying
changes in recessions are occurring during the thawing period. Separate
storage-discharge analyses combined with preceding winter conditions
demonstrated that especially cold winters with little snow yield springs
and summers with more linear storage-discharge relationships. We show
that streamflow recession analysis shows ongoing hydrological change of
an arctic landscape as well as offers new metrics for tracking the
change across arctic and sub-arctic landscapes.