Abstract
ABSTRACT This empirical study explores shifts in stable water isotopic composition for a subarctic catchment located in northern Sweden as it transitions from spring freshet to summer low flows. Relative changes in the isotopic composition of streamflow across the main catchment and fifteen nested subcatchments are characterized in relation to the isotopic composition of precipitation. With our sampling campaign, we explore the variability in stream-water isotopic composition that originates from precipitation as the input shifts from snow to rain and as landscape flow pathways change across scales. The isotopic similarity of high-elevation snowpack water and early season rainfall water seen through our sampling scheme made it difficult to truly isolate the impact of seasonal precipitation phase change on stream-water isotopic response. This highlights the need to explicitly consider the complexity of arctic and alpine landscapes when designing sampling strategies to characterize hydrological variability via stable water isotopes. Results show a potential influence of evaporation and source water mixing both spatially (variations with elevation) and temporally (variations from post-freshet to summer flows) on the composition of stream water across Miellajokka. As such, the data collected in this empirical study allow for initial conceptualization of the relative importance of, for example, hydrological connectivity within this mountainous, subarctic landscape.
Highlights
Freshet is an extreme period of the year in high-latitude, arctic, and subarctic systems
On May 22, the snowpack was completely gone at the low elevation site, while the middle elevation pack had decreased by 57 percent and 42 percent for the open and forested coverage, respectively
To further explore the potential controls on spatiotemporal variability of stable water isotopes across the Miellajokka region, we considered the relationships between stream water lines for each individual subcatchment (Table 6) and the topographically derived characteristics available (i.e., Table 1)
Summary
Freshet (spring flood) is an extreme period of the year in high-latitude, arctic, and subarctic systems In these cold and snow-dominated regions, freshet is a period of rapidly melting snow and ice that typically produces the largest annual flows in rivers. Climate change is anticipated to shift precipitation from snow to rain, which could have considerable impacts on the amount of freshet water and the chemical composition of freshet waters and streamflow throughout the year. This latter aspect is extremely important for arctic and subarctic aquatic ecosystems, because terrestrialderived chemistry is often the main source of biological energy. The composition of and any potential for changes in source water that enters into arctic and subarctic river systems may have considerable implications
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