Long-Term Heat Flux Formation Of The Large Russian Arctic Rivers And Its Transformations In Estuaries Under The Influence Of Climate-Induced And Dam-Induced Effects

Abstract

The heat flux of the large rivers flowing into the Arctic seas of Russia plays an essential role in the thermal and ice regime of the lower reaches of these rivers and the southern part of the Arctic seas. However, estimates of the total value of heat flux and its spatial-temporal distribution require clarification. In this research, we analyzed monthly, and yearly water temperature data from 55 gauges and water flow data from 35 gauges in the lower reaches of the rivers of the Russian Arctic northerner of 60 N. These rivers are: Onega, Northern Dvina, Mezen, Pechora, Ob, Nadym, Pur, Taz, Yenisei, Khatanga, Anabar, Olenek, Lena, Yana, Indigirka, Alazeya, Kolyma and their main tributaries. The collected data series covers 1930-2018, focusing more on 1960–2018. We used Spearman trend tests and Mann-Whitney U-test to clarify changes in the thermal regime of study rivers. Our estimations showed that heat flux did not significantly increase in the past three decades on most rivers except Yenisei and Yana lowlands. Water temperatures on rivers monotonically increased after 1960, especially in May and June, but without statistical significance. The role of dams in the water temperature regime is observed for nearly 500 km lower dams, but it is not observed in their lowlands and mouths. We also identified the decrease in water temperatures and heat flux in river lowlands, estuaries and deltas up to 25% for Yenisei lowlands.