ИСТИНА

Water and sediment supply are essential to the health of deltaic ecosystems. Diverse datasets were integrated together to better understand how climate change is shifting the supply of water and sediment to the largest polar distributary channel pattern – the Lena River Delta, Russia. Results show an increase in warming rate from an average air temperature of 4.1 °C for the period 1950–99 to 6.1 °C during 2000–21 over the Lena Delta, which is higher than in the adjacent polar regions. Streamflow and sediment yield entering the Lena Delta have increased since 1988 by 56.3 km3 and 6.1×106 t, respectively; meanwhile, the Lena River water temperature increases in June, July–August and September were found to be as much as 1.1, 0.6 and 0.05 °C. These changes do not influence flow partitioning between the main distributaries of the delta, but have a pronounced effect on sediment regimes in particular parts of the delta. Based on analyses of correlations between various hydroclimatic drivers and sediment concentration changes across particular distributaries of the Lena Delta extracted from Landsat datasets, bank degradation driven by thermal erosional processes (which are in turn related to air and soil temperature increases) is proved to be the primary factor of the sediment regime in the delta. The study also highlights that sediment load changes are sensitive to wind speed due to remobilization of bottom sediment. Multilinear regression showed that sums of daily air temperature and wind speed over 3 days make the most pronounced contribution to sediment concentration changes in the delta. The results also indicate that carbon transport across the delta (both POC and DOC) depends on sediment transport conditions and water discharge and might increase by up to 10% due to observed hydroclimatic changes. The Lena Delta can be recognized as the global hot spot in terms of the hydrological consequences of climate change which together with streamflow alters sediment regimes, stream hydromorphology and carbon transport.