Influence of the Mackenzie River plume dispersal on the dissolved barium concentrations in the upper Canada Basin waters

Abstract

Dissolved barium has been shown to have the potential to track river runoff in marine waters. In this study, the distribution of dissolved barium was determined in the upper 450 m waters of the Canada Basin along the Joint Ocean Ice Study 140°W transect in August/September 2019–2021. In these highly stratified Canada Basin waters, the dBa concentrations increased from 42.51 nmol kg⁻¹ in the Atlantic waters to 128.91 nmol kg⁻¹ in the polar mixed layer. The dispersal of Ba-rich surface waters found over the slope and outer shelves is attributed to the Mackenzie River plume. These waters were either confined nearshore with northwest winds (2019 and 2020) or entrained into the Beaufort Gyre interior under easterly winds (2021). In the subsurface layers, the vertical variation in barium concentration in the Pacific Winter Water and Atlantic Halocline waters showed evidence of mixing. Dissolved Ba dynamics provide a window into the complex interplay between physical, biological, and chemical processes in Arctic waters, making it a valuable tracer for understanding ocean circulation, nutrient transport, and ecosystem functioning in the rapidly changing Arctic region.