Long-term, time-series collections of sinking particles using deep-sea sediment traps provide critical insights into the origin and dynamics of particulate organic carbon (POC) in the deep ocean. Radiocarbon is an effective tracer for distinguishing modern, recently fixed carbon (including the bomb-radiocarbon signal) from aged carbon sources. Here, we present radiocarbon (Δ¹⁴C) values of sinking POC collected at 300 m (500 m), 1000 m, and 2000 m depths at a long-term monitoring station in the Ulleung Basin (UB), located in the southwestern East Sea (Japan Sea). The Δ¹⁴C values of sinking POC indicate heterogeneous source inputs, suggesting that lateral transport and sediment resuspension contribute significantly to deep POC supply in addition to vertical export. The Δ¹⁴C values also exhibit a decreasing trend over time, consistent with the decline of the atmospheric bomb-radiocarbon signal. These findings demonstrate the utility of Δ¹⁴C in evaluating the efficiency and complexity of the biological carbon pump. Given the rapid turnover and high climate sensitivity of the UB, the implications for understanding oceanic carbon cycling will be discussed.

radiocarbon,sinking particle,sediment trap,biological carbon pump,particulate organic carbon