Quantitative Assessment of Factors Contributing to Variations in Sea Surface pCO2 in the Pacific Sector of the Arctic Ocean

Abstract

AbstractTo quantitatively assess seasonal variations in the partial pressure of carbon dioxide (pCO2) in the Pacific sector of the Arctic Ocean (Canada Basin and Chukchi Sea) in 2021, water temperature, salinity, chlorophyll‐a, pCO2, dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrients were measured. During summer 2021, surface water pCO2 in our study area (315 ± 41 μatm) was undersaturated with respect to the atmosphere (404 ± 4 μatm), and the ocean was a sink for atmospheric CO2 (−10.5 ± 11.0 mmol C m−2 day−1). Using DIC, TA, and nutrients in the temperature minimum layer, we estimated the under‐ice pCO2 in the water during the previous winter and calculated changes in pCO2 (δpCO2) due to temperature changes, freshwater inflow, biological activity, and other factors (gas exchange and advection) from winter to summer. In the Chukchi Sea, biological activity and temperature changes had significant impacts on pCO2, whereas in the Canada Basin, the influx of freshwater caused a significant decrease in pCO2. Our results suggested that different types of freshwaters had different effects on pCO2, with sea ice meltwater having a greater effect on reducing pCO2 than river water or snowmelt water. We therefore emphasize the importance of freshwater type and proportion, as well as freshwater supply, for prediction of future pCO2 changes.