5:15 PM - 7:15 PM
[AOS13-P09] Quantifying the Impacts of Riverine Carbon and Nutrient Fluxes on Arctic Ocean Acidification
Keywords:Arctic Ocean Acidification, River Water, Biogeochemical Fluxes, Model Simulation
Arctic rivers transport substantial freshwater and biogeochemical materials into the ocean, playing important roles in Arctic Ocean acidification (OA). This study quantitatively evaluates the impacts of riverine biogeochemical fluxes (R-BGC; carbon and nutrients) on the Arctic marine carbonate system and OA using multi-decadal simulations (1979–2018) with a pan-Arctic sea ice–ocean model. For more realistic experiments, this study incorporated improved initial and lateral boundary conditions for carbonate properties, observation-based riverine biogeochemical data, and interannually varying riverine freshwater discharge from a land model.
The model simulated declining trends in aragonite saturation state (Ω) and pH in most Arctic regions, regardless of R-BGC. Increased riverine freshwater intensified OA due to its dilution effect. Compared to simulations with only freshwater discharge, including R-BGC led to positive anomalies in Ω and pH (~0.14 and ~0.03 in central basins, ~0.15 and ~0.06 in shelf seas, respectively). In central basins, these anomalies were primarily driven by riverine carbon (total alkalinity and dissolved inorganic carbon), while in shelf seas, nutrient fluxes (nitrate and silicate) contributed ~14% and ~32% of the anomalies by enhancing primary production and lowering seawater pCO2. R-BGC mitigated OA (ΔΩ = –1.53×10–3 year–1, ΔpH = –0.56×10–3 year–1) in regions with riverine freshwater accumulation, such as the Canada Basin, Chukchi Cap, Eurasian Basin, and East Siberian Sea. These findings highlight the critical role of R-BGC in OA projections.
The model simulated declining trends in aragonite saturation state (Ω) and pH in most Arctic regions, regardless of R-BGC. Increased riverine freshwater intensified OA due to its dilution effect. Compared to simulations with only freshwater discharge, including R-BGC led to positive anomalies in Ω and pH (~0.14 and ~0.03 in central basins, ~0.15 and ~0.06 in shelf seas, respectively). In central basins, these anomalies were primarily driven by riverine carbon (total alkalinity and dissolved inorganic carbon), while in shelf seas, nutrient fluxes (nitrate and silicate) contributed ~14% and ~32% of the anomalies by enhancing primary production and lowering seawater pCO2. R-BGC mitigated OA (ΔΩ = –1.53×10–3 year–1, ΔpH = –0.56×10–3 year–1) in regions with riverine freshwater accumulation, such as the Canada Basin, Chukchi Cap, Eurasian Basin, and East Siberian Sea. These findings highlight the critical role of R-BGC in OA projections.