Data Sheet 1_Effects of Langmuir circulation parameterization on seasonal air–sea CO2 exchange in the Bering Sea.pdf

Intensified ocean mixing can alter both the vertical temperature profile and biogeochemical states. Using a physical–biogeochemical coupled ocean model, we examine the impact of parameterized Langmuir circulation (LC) on the ocean carbon system in the Bering Sea. While LC has limited influence in summer, it significantly enhances turbulent mixing in winter, leading to an average wintertime mixed-layer deepening of about 11%. In the presence of a winter temperature inversion, LC-driven mixing enhances the entrainment of warmer subsurface water into the surface, increasing the surface ocean partial pressure of CO2 (pCO2). Concurrently, intensified vertical mixing entrains carbon-rich deep water into the surface layer, further elevating wintertime surface pCO2. By decomposing pCO2 into thermal and non-thermal components, we find that changes in dissolved inorganic carbon (DIC) supply exert a stronger influence than temperature-driven change, increasing the non-thermal pCO2 by up to 8.5 µatm in March and amplifying the seasonality of non-thermal processes. The thermal component also increases pCO2 by about 4.3 µatm in March, but its contribution to the seasonal amplitude is relatively small. These results demonstrate that enhanced vertical mixing combined with a winter temperature inversion can substantially alter pCO2 and air–sea CO2 fluxes in high-latitude regions; in regions without such inversions, thermal and non-thermal LC effects are likely to offset one another.