Size Distribution, Surface Coverage, Water, Carbon, and Metal Storage of Thermokarst Lakes in the Permafrost Zone of the Western Siberia Lowland

Abstract

Despite the importance of thermokarst (thaw) lakes of the subarctic zone in regulating greenhouse gas exchange with the atmosphere and the flux of metal pollutants and micro-nutrients to the ocean, the inventory of lake distribution and stock of solutes for the permafrost-affected zone are not available. We quantified the abundance of thermokarst lakes in the continuous, discontinuous, and sporadic permafrost zones of the western Siberian Lowland (WSL) using Landsat-8 scenes collected over the summers of 2013 and 2014. In a territory of 105 million ha, the total number of lakes >0.5 ha is 727,700, with a total surface area of 5.97 million ha, yielding an average lake coverage of 5.69% of the territory. Small lakes (0.5-1.0 ha) constitute about one third of the total number of lakes in the permafrost-bearing zone of WSL, yet their surface area does not exceed 2.9% of the total area of lakes in WSL. The latitudinal pattern of lake number and surface coverage follows the local topography and dominant landscape zones. The role of thermokarst lakes in dissolved organic carbon (DOC) and most trace element storage in the territory of WSL is non-negligible compared to that of rivers. The annual lake storage across the WSL of DOC, Cd, Pb, Cr, and Al constitutes 16%, 34%, 37%, 57%, and 73%, respectively, of their annual delivery by WSL rivers to the Arctic Ocean from the same territory. However, given that the concentrations of DOC and metals in the smallest lakes (<0.5 ha) are much higher than those in the medium and large lakes, the contribution of small lakes to the overall carbon and metal budget may be comparable to, or greater than, their contribution to the water storage. As such, observations at high spatial resolution (<0.5 ha) are needed to constrain the reservoirs and the mobility of carbon and metals in aquatic systems. To upscale the DOC and metal storage in lakes of the whole subarctic, the remote sensing should be coupled with hydrochemical measurements in aquatic systems of boreal plains.

Impact of snow deposition on major and trace element concentrations and elementary fluxes in surface waters of the Western Siberian Lowland across a 1700 km latitudinal gradient

“…These lakes are shallow (0.5-1.5 m depth) water bodies representing the largest reservoir of surface waters in western Siberia, north of 62 • N (Polishchuk et al, 2017). The average concentration of major and trace elements in thermokarst lakes of various size (Manasypov et al, 2014) can be compared with those in snow water collected in this study across the same latitudinal gradient.…”

Riverine particulate C and N generated at the permafrost thaw front: case study of western Siberian rivers across a 1700 km latitudinal transect

“…Given the very short transit time of water from the surrounding peat to the lakes via suprapermafrost flow (Ala-aho et al, 2018a, b;Raudina et al, 2018), the allochthonous chromophoric DOM-rich material from peat soil water that arrives to the lakes may be subjected to fast degradation and coagulation, as shown in Scandinavian lakes (Kortelainen et al, 2006b;. Second, the peat abrasion at the border of the thermokarst lakes and thaw ponds, which are highly abundant in the territory (Polishchuk et al, 2017(Polishchuk et al, , 2018, occurs due to wave erosion and thermoabrasion (Shirokova et al, 2013;Manasypov et al, 2015). The physical disintegration of peat at the lake coast likely generates a large amount of suspended organic-rich material that can be exported to hydrological networks during, for example, lake drainage or already existing connecting channels (Kirpotin et al, 2008(Kirpotin et al, , 2011.…”

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

“…As a result of low gradients and poor drainage, the landscape is characterized by waterlogged peatlands with a mosaic of lakes and wetlands (Frey et al 2007. The lake coverage is 5.7% on average but achieves 30% in some places (Polishchuk et al 2017).…”