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  • 1. Krickov, Ivan V.
    et al.
    Lim, Artem G.
    Manasypov, Rinat M.
    Loiko, Sergey V.
    Shirokova, Liudmila S.
    Kirpotin, Sergey N.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pokrovsky, Oleg S.
    Riverine particulate C and N generated at the permafrost thaw front: case study of western Siberian rivers across a 1700km latitudinal transect2018Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, nr 22, s. 6867-6884Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In contrast to numerous studies on the dynamics of dissolved (< 0.45 mu m) elements in permafrost-affected highlatitude rivers, very little is known of the behavior of river suspended (> 0.45 mu m) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physiogeographical 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 km(2) 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 V 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 degrees 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.

  • 2. Pokrovsky, Oleg S.
    et al.
    Bueno, Maite
    Manasypov, Rinat M.
    Shirokova, Liudmila S.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Amouroux, David
    Dissolved organic matter controls seasonal and spatial selenium concentration variability in thaw lakes across a permafrost gradient2018Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 52, nr 18, s. 10254-10262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Little is known about the sources and processing of selenium, an important toxicant and essential micronutrient, within boreal and sub-arctic environments. Upon climate warming and permafrost thaw, the behavior of Se in northern peatlands becomes an issue of major concern, because a sizable amount of Se can be emitted to the atmosphere from thawing soils and inland water surfaces and exported to downstream waters, thus impacting the Arctic biota. Working toward providing a first-order assessment of spatial and temporal variation of Se concentration in thermokarst waters of the largest frozen peatland in the world, we sampled thaw lakes and rivers across a 750-km latitudinal profile. This profile covered sporadic, discontinuous, and continuous permafrost regions of western Siberia Lowland (WSL), where we measured dissolved (<0.45 mu m) Se concentration during spring (June), summer (August), and autumn (September). We found maximum Se concentration in the discontinuous permafrost zone. Considering all sampled lakes, Se exhibited linear relationship (R-2 = 0.7 to 0.9, p < 0.05, n approximate to 70) with dissolved organic carbon (DOC) concentration during summer and autumn. Across the permafrost gradient, the lakes in discontinuous permafrost regions demonstrated stronger relationship with DOC and UV-absorbance compared to lakes in sporadic/isolated and continuous permafrost zones. Both seasonal and spatial features of Se distribution in thermokarst lakes and ponds suggest that Se is mainly released during thawing of frozen peat. Mobilization and immobilization of Se within peat-lake-river watersheds likely occurs as organic and organo-Fe, Al colloids, probably associated with reduced and elemental Se forms. The increase of active layer thickness may enhance leaching of Se in the form of organic complexes with aromatic carbon from the deep horizons of the peat profile. Further, the northward shift of permafrost boundaries in WSL may sizably increase Se concentration in lakes of continuous permafrost zone.

  • 3.
    Serikova, Svetlana
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pokrovsky, O.S.
    University of Toulouse.
    Vorobyev, S.N.
    Tomsk State University.
    Krickov, I.V.
    Tomsk State University.
    Lim, A.G.
    Tomsk State University.
    Siewert, Matthias B.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Vachon, Dominic
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Carbon emission from the boreal floodplain of Ob’ RiverManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The Ob’ River floodplain is the second largest floodplain in the world. Despite its vast area, estimates of carbon (C) emissions from the Ob’ River floodplain are largely absent. Here we present seasonal C emission and water area extent from the main channel and the floodplain along a ~4 km reach in the boreal zone of the Ob’ River. We find strong seasonality in water area extent of the Ob’ main channel (~1.8 km2) and floodplain (~3 km2) with water covering 34% of land during flood and subsequently declining to ~16 and 14% during summer and autumn baseflow, respectively. The C emissions also showed seasonal differences over the open water period ranging from 4.66 to -4.25 g C m-2 d-1 for the Ob’ main channel and from 0.03 to 1.42 g C m-2 d-1 for the floodplain. The total annual C emission from the study reach was ~940 ± 744 t C yr-1 with the floodplain accounting for ~16%. The contribution of the floodplain to the net river C evasion can be even greater in northern regions of the Ob’ River basin, where floodplain soils are more C-rich and are underlain by permafrost, and in years with more extensive flooding.

  • 4.
    Serikova, Svetlana
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pokrovsky, O.S.
    University of Toulouse.
    Vorobyev, S.N.
    Tomsk State University.
    Rocher-Ros, Gerard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Denfeld, Blaize A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Carbon emission from Western Siberian Inland WatersManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Western Siberia, with large carbon (C) stocks stored in permafrost, is a key region in the global C cycle. This region contains numerous rivers and lakes, including Arctic’s largest watershed – the Ob’ River, yet the role of inland waters in the regional C cycle is unknown. Here we quantify C emission from Western Siberian inland waters to ~0.1 ± 0.01 Pg C yr-1. The C emission exceeds region’s C export to the Arctic ocean by ~9-fold suggesting that any increase in region’s terrestrial C export will be largely evaded through inland waters and highlighting the need to account for coupled land-water C cycle to understand its response to warming.

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