Abstract
Abstract. In contrast to numerous studies on the dynamics of dissolved (<0.45 µm) elements in permafrost-affected high-latitude rivers, very little is known of the behavior of river suspended (>0.45 µm) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physio-geographical landscape parameters (bogs, forest and lake coverage of the watershed) on RSM and particulate C, N and P concentrations in river water, we sampled 33 small and medium-sized rivers (10–100 000 km2 watershed) along a 1700 km N–S transect including both permafrost-affected and permafrost-free zones of the Western Siberian Lowland (WSL). The concentrations of C and N in RSM decreased with the increase in river watershed size, illustrating (i) the importance of organic debris in small rivers which drain peatlands and (ii) the role of mineral matter from bank abrasion in larger rivers. The presence of lakes in the watershed increased C and N but decreased P concentrations in the RSM. The C:N ratio in the RSM reflected the source from the deep soil horizon rather than surface soil horizon, similar to that of other Arctic rivers. This suggests the export of peat and mineral particles through suprapermafrost flow occurring at the base of the active layer. There was a maximum of both particulate C and N concentrations and export fluxes at the beginning of permafrost appearance, in the sporadic and discontinuous zone (62–64∘ N). This presumably reflected the organic matter mobilization from newly thawed organic horizons in soils at the active latitudinal thawing front. The results suggest that a northward shift of permafrost boundaries and an increase in active layer thickness may increase particulate C and N export by WSL rivers to the Arctic Ocean by a factor of 2, while P export may remain unchanged. In contrast, within a long-term climate warming scenario, the disappearance of permafrost in the north, the drainage of lakes and transformation of bogs to forest may decrease C and N concentrations in RSM by 2 to 3 times.
Highlights
High-latitude rivers are most vulnerable to ongoing climate change via altering their hydrological regime (Bring et al, 2016) and widespread permafrost thaw that stimulates nutrient release (Vonk et al, 2015)
Mean bulk RSM concentration in the Western Siberian Lowland (WSL) river waters did not depend on the season of open-water period of the year and was equal to 7.1 ± 3.9, 8.1 ± 4.1 and 7.0 ± 3.7 mg L−1 in spring, summer and autumn, respectively (Table 1)
Low-bulk RSM concentrations in WSL rivers stem from low runoff in this flat peatland province of boreal and subarctic zones
Summary
High-latitude rivers are most vulnerable to ongoing climate change via altering their hydrological regime (Bring et al, 2016) and widespread permafrost thaw that stimulates nutrient release (Vonk et al, 2015). For carbon (C), the particulate fraction (POC) contributes substantially to the total organic C export from the continent to the ocean (Schlesinger and Melack, 1981; Lal, 2003; Ludwig and Probst, 1996; Galy et al, 2015; Li et al, 2017; Coppola et al, 2018); a 2-fold increase of Arctic rivers POC fluxes by 2100 is predicted (Gordeev and Kravchishina, 2009). The reasons for strong variations of POC in freshwater are not yet fully understood Krickov et al.: Riverine particulate C and N across permafrost gradient
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call