Аннотация:River water temperature serves as a critical indicator of numerous biological and chemical processesessential for ecosystem support and water quality maintenance. River heat flux which is relatedto river water temperature plays an important role in the formation of water temperature in riverscrossing various natural zones, in the formation of ice phenomena, including ice cover of ArcticOcean, as well as the microclimate of river valleys, especially on big rivers. The long-term variabilityof both river water temperature and river heat flux is studied relatively poorly in the permafrost zone.We have tried to close some gaps in our knowledge about the long-term variability and conditionsof formation of water temperature and heat flux in the permafrost zone of the Russian Arctic (northof 60 N), as well as in the basin of Lake Baikal. For the analysis, we collected data on monthlywater temperature (counted from 2 times a day observations) from the beginning of observations(1930-1950) to 2022 and for 10-day periods from 1985 to 2022 (also counted from twice a dayobservations). We used data from both meteorological stations and reanalysis for estimations ofthe role of different factors in formation of studied rivers characteristics. It has been revealed thatthe air temperature in the permafrost zone is an important, however, not always a determining factorin the formation of water temperature and heat flux. Long-term changes in water temperature onrivers have been estimated, and it has been shown that all rivers experience an increase in watertemperature, which is quite significant during the transition seasons. The intensity of the increasein river water temperature is not as significant as previously assumed.
