Accelerated permafrost degradation accelerates erosion of the Lena River bed

Such a conclusion was made by Russian scientists after studying the character of sediment movement through the basins of the three largest rivers of Northern Eurasia – the Ob, Yenisei, and Lena. According to the results of the study, channel erosion on the Lena is almost twice as high as on the Ob, and almost ten times higher than on the Yenisei.

Scientists say that the degradation of permafrost leads to more sediment flowing into the rivers. The basins of the three rivers cover about 14% of Eurasia as a whole, and they also carry enormous amounts of water and heat from the central regions of the continent toward the Arctic. Because of this, they play a critical role in the ecosystems of northern Eurasia, as well as in shaping the climate of the Arctic.

According to the researchers, each year all three rivers produce a huge amount of sediment, ranging from 0.9 to 1.6 billion tons, which is comparable to the mass of these particles in the waters of the Amazon, the largest river in the world. However, only a small fraction of suspended solids, about 4 percent, reaches the Arctic Ocean. Most of them do not reach the lower streams and are trapped on slopes, in floodplains and channels, which noticeably affects the appearance of all three rivers.

The Ob basin is characterized by a high level of soil erosion associated with agriculture in its upper reaches. The Lena River is eroding two and ten times faster than the Ob and Yenisei, respectively, due to recently accelerated permafrost degradation in Eastern Siberia.

A group of geographers led by Sergey Chalov, associate professor at Lomonosov Moscow State University, conducted a comprehensive analysis of the factors influencing the nature of the transport of various sediments by the Ob, Yenisei, and Lena, the three largest waterways of Northern Eurasia. To do this, they used data collected from remote sensing systems and created mathematical models describing the nature of water movement in the Ob, Yenisei, and Lena throughout these rivers.

Modern technology and databases have allowed scientists to answer the question of where, how much, and how sediment flows into the Arctic seas from the territories of the Ob, Yenisei, and Lena basins. These fundamentally important assessments will make it possible to predict the risks of pollutant transport by rivers and their changes in future climatic conditions.

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