Climate Change and the Ob River: A Reassessment of Major and Trace Element Fluxes to the Arctic Ocean

Abstract

Over the past few decades, climate warming has driven alterations in both the discharge volume and biogeochemical composition of Arctic riverine fluxes. This study investigated the content of macro- and microelements in the lower reaches of the Ob River (western Siberia). Seasonal sampling was performed over a four-year period (2020–2023) during the main hydrological seasons (winter low water, spring-summer floods, and early fall low water) at three river stations. The results revealed significant seasonal variations in the elemental content of the Ob River water associated with changes in catchment inputs, physical and chemical conditions of the aquatic environment, and the amount and composition of incoming suspended sediment. During high water flow events in the Ob River, the concentration of suspended solids increased substantially. During the winter period when the Ob River was ice-covered, a two- to three-fold rise was observed in the concentration of Na, Mg, Ca, K, Si, and Mn. Having accounted for these seasonal variations in water chemistry, we were able to refine our estimates of elemental export to the Arctic Ocean. Compared to estimates from previous studies, we observed 2.3-fold higher dissolved loads of Mn, and the dissolved loads were higher by 2.1-fold for Zn, 1.6-fold for Fe, and 1.4-fold for Pb. The observed rise in elemental export is likely attributable to a confluence of factors, including permafrost thaw, enhanced water inflow from wetland catchments, and intensifying snowfall leading to increased flood runoff.