Permafrost and lakes control river isotope composition across a boreal Arctic transect in the Western Siberian lowlands

Abstract

The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South-North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10-10 5 km 2 ) and permafrost coverage (0%-70%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance.

Spatially-distributed tracer-aided runoff modelling and dynamics of storage and water ages in a permafrost-influenced catchment

“…This observation agrees well with results of the STARR model, suggesting that streamflow water during freshet is primarily displaced old water that has resided in the watershed over-winter. This is also consistent with the findings of recent small catchment observations at Trail Valley in Canada 20 and larger scale observations in the watershed of the River Ob in Russia (Ala-aho et al, 2018b(Ala-aho et al, , 2018a.…”

Global Isotope Hydrogeology―Review

“…Relative to their areas, tropical and high‐latitude lands are underrepresented in the primary literature, whereas northern mid‐latitude catchments are overrepresented. Recent works are ameliorating this by studying tropical (Jacobs et al, ), high‐elevation, and high‐latitude systems (e.g., Ala‐aho et al, , ; Ren et al, ; Tetzlaff et al, ; Yi et al, ). Continuing streamflow, groundwater, and precipitation isotopic data set development in these regions may help to monitor consequences of atmospheric warming on hydrologic processes (Lyon et al, ; Wilusz et al, ).…”

Dissolved organic matter biodegradation along a hydrological continuum in permafrost peatlands

“…They were sampled in July 2018 and used as substrates for incubation. We sampled two supra-permafrost waters from peatland, one on a mound and one on a hollow (see sampling details in Raudina et al, 2018); two lakes: organic-rich Chernoe and organic-poor Trisino; two streams: the one close to the outlet of the lake and another one located far from this outlet (Lymbydyakha); and finally one medium-size river Pyakopur that flows through peatland and forest (Ala-aho et al, 2018).…”