Sources and Dynamics of Dissolved Organic Carbon in Kongsfjorden: Insights From Radiocarbon Analysis

The Arctic is undergoing rapid warming, resulting in accelerating glacier melt and release of nutrients, particles, and organic matter into coastal fjord systems. Kongsfjorden, a fjord in Svalbard, serves as a natural laboratory for investigating climate-driven shifts in high-latitude fjord ecosystems and their broader implications for the Arctic. To examine dissolved organic carbon (DOC) sources and cycling in Kongsfjorden, we collected samples of seawater, floating ice, and river water in June 2023 and analyzed ¹⁴C and ¹³C in DOC. Radiocarbon values of DOC (as in Δ¹⁴C) in fjord seawater ranged from −302‰ to −253‰, while values in the Bayelva River were higher, suggesting a contribution of younger, terrigenous DOC. However, stable carbon isotope results suggested rapid removal of riverine DOC after entering the fjord. Additionally, differences in Δ¹⁴C values between the inner and outer fjord reflected varying contributions from surface primary production and glacial meltwater inputs.