Coupled Hydroclimatic and Lake Change Patterns in Western Siberia

Abstract:

Thermokarst lakes are dependent on permafrost. Thermokarst lakes and wetlands dominate the peat-forming lowlands of the Nadym and Pur river basins in Western Siberia. Recent warming and potential permafrost thaw has initiated fluctuations in the number and total area of lakes in these basins. We use remote sensing (Landsat images) to distinguish spatially explicit changes. Further, through coupled analysis of hydrological data, we also identify characteristic patterns of lake-area and hydroclimatic change and assess the role of permafrost in such patterns. Our results reveal spatially heterogeneous lake-change patterns with drained lakes appearing alongside stable lakes. Such heterogeneity likely indicates permafrost thaw as a main driver of change rather than shifts in precipitation and evapotranspiration, which would yield more homogenous change patterns. The total area and number of lakes fluctuated over time with both appearing and disappearing lakes and a high number of drainage events. However, the size distribution of lakes remained essentially constant over the investigated time periods. The role of permafrost degradation on thermokarst lakes appears to be localized and thereby not detectable in basin-averaged properties of the entire Nadym and Pur basins. Regardless, specific sub-basins can exhibit long-term sustained lake change with coupled hydroclimatic changes. These locations are vital as they offer clear windows to consider the possible manifestations of global climate change and its influence on biogeochemical cycles and carbon effluxes.