| چکیده انگلیسی مقاله |
Massive northern rivers transport huge quantities of water and constituents from the continents to the Arctic Ocean due to catchment and channel erosion. Within the Russian sector of Arctic, they are least studied regarding quantitative characteristics of sediment load, transport mode of sediment grain size and particulate heavy metals. Lena and Kolyma rivers estuaries are among largest deltas in the Arctic. Both are located in the zone of continuous near-surface permafrost. It is an important sedimentation barriers which declines delivery of sediments into the Arctic Ocean. This study aims at assessment of long-term and seasonal changes of sediment budget in Lena and Kolyma deltas based on remote sensing dataset. Landsat images since 1999 were applied during ice-free period, from June to September. The sediment concentration (SC) at the Lena delta topset was compared with SC data at the outlets of: the Main (Tit-Ary island), Olenekskaya, Tumatskaya, Trofimovskaya and Bykovskaya channels to calculate suspended sediment budget in delta. For Kolyma delta SC data between delta topset in the vicinity of Cherskiy and outlets of the two main channels of the delta: Pokhodskaya and Kamennaya. The sediment concentration was calculated based on the archive Landsat images (more than 110 images). The single model with the high accuracy of sediment concentration’s detection was used for calculation of sediment suspensions. This model was based on calibration of pixels’ reflection power from the satellite images according to measured turbidity data in hydrological studies on the middle Lena River (July 2016/June-July 2020) – 21/18 measurements and on the estuary section of the river Kolyma (July-August 2019) – 12 measurements. We adapted the turbidity retrieving technique and data processing algorithm and evaluated the accuracy of turbidity modeling. The study reveals significant effects on sediment budget from seasonal variability of weather conditions. Air temperature influence thermal bank erosion along largest channel and lead to longitudinal increase of sediment loads. The increase of the daily average air temperature plays critical role in the degradation of permafrost and the activation of the processes of thermal erosion and thermal denudation. |
