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Abstract

The erosion of permafrost outcrops (yedoma) in the valleys of large Arctic rivers is considered as an important source of suspended sediment and carbon inflow into the natural waters of the Lena, Kolyma, Yana, Indigirka Rivers and further into the Arctic Ocean. Based on combination of on-situ sediment transport observations done in 2021 and 2022 (reconnaissance, ADCP measurements, laser optics LISST profiles), application of remote sensing data and 2D hydrodynamic and morphological modelling by MIKE 21C, we explored the impact of Duvanny Yar Yedoma ice complex, the largest inland outcrop of permafrost, on lower reaches of the Kolyma river. An increase of around 20% in the turbidity of the Kolyma River was revealed during the summer low-flows in the reach downstream of the yedoma. The influx of suspended matter due to the melting of the slopes of the ice complex on hot summer days in the emerging network of turbidity streams was estimated at a value of more than 5 kg/s. The effect of thermal destruction of the ice complex is confirmed by a statistically significant relationship between the length of the turbidity plume propagating from Duvanny Yar Yedoma downstream the Kolyma river and the average daily air temperatures air temperature in this area. Thus, for the first time, quantitative data have been obtained confirming the role of activation of destruction of permafrost in the formation of large river sediment runoff.