Long-term Changes of Streamflow and Heat Transport of two Largest Arctic Rivers of European Russia, Severnaya Dvina and Pechora

Abstract:

Analyses of time series of hydrological characteristics of the Northern Eurasian rivers on the century time scale show lengthy periods (phases with duration of 10 to 15 years and more), when these characteristics remained systematically less or higher than their long-term values estimated for the entire period of observations. For the warm half of the year (May through October), we revealed contract phases of increased and decreased streamflow on the Severnaya Dvina River (at the Ust’-Pinega river gauge) and on the Pechora River (at the Ust’ Tsil’ma river gauge). The boundaries of contrast phases were determined using normalized cumulative deviation curves in combination with Student’s test of the statistical homogeneity of the data series. During the 1930-2016 observation period, the features of these contrast phases of streamflow are quite different. In the Severnaya Dvina flow, there were four phases of nearly same duration (from 13 to 18 years). Initially, there was a decreased flow phase. Thereafter, since the end of the 1950s, this phase ceased to be and since 1985 we observed the increased flow phase. The last phase (from the late 1990s up to date) has been again a decreased flow period. In the Pechora River streamflow, we observe first a lengthy decreased flow phase from the observation inception up to 1955. Thereafter, there were two short 10-year-long periods of increased and decreased flows respectively and since the 1981 there was a 30-year-long phase of increased flow. Only in 2010, this phase was replaced by the decreased flow phase. In the multiannual heat transport by both Rivers, we revealed two major lengthy contrast phases that changed their sign from decreased to increased heat transport in the early 1980s. Since the early 2010s (as well as for the streamflow), we observe a switch to the phase of decreased heat transport. This last switch was observed for many components of geo-flow (water, heat, and matter) at the main Arctic Rivers of Northern Eurasia. For the Severnaya Dvina River, the differences in mean water flow and heat transport between the contrasting values of their phases (compared to the low flow/heat mean values) are 14-19% and 13-20% respectively. For the Pechora River, these differences are 10-12% and 12% respectively. Russian Foundation for Basic Research (grant 18-05-60240) supported this study.