Fig. 2: Processes that lead to a reduction in the oceanic uptake of CO₂ in the North Pacific during PMHWs.

a 2009–2017 average F_CO2 anomalies (black dot) and its Taylor decomposition (vertical bars). The contribution of temperature, Dissolved Inorganic Carbon (DIC), Alkalinity (ALK), salinity, wind and atmospheric partial pressure of CO₂ to F_CO2 anomalies observed during PMHWs in the North Pacific CO₂ sink region for the 2009–2017 period were calculated using a first order Taylor expansion derived from the biogeochemical reanalysis (see methods section). The “total” bar corresponds to the sum of all contributing terms and corresponds to the Taylor approximation of F_CO2 anomalies (black dot). The good agreement between the two implies that F_CO2 anomalies are well approximated by the Taylor decomposition. The error bars correspond to the 95% confidence interval. b Contribution of horizontal, vertical diffusion, vertical advection, dilution and concentration due to freshwater fluxes, air-sea CO₂ flux density, a residual term and biological activity to the rate of change (tendency or trend) of DIC anomalies during PMHWs in the North Pacific CO₂ sink region for the 2009–2017 period (see methods section). The vertical bars represent the slope from linearly regressing each forcing term to the DIC anomalies trend²⁸. A linear regression slope close to 1 indicates that a particular term produces in-phase anomalies of comparable magnitude. A slope near zero indicates that the term is not important in generating anomalies. The error bars correspond to 95% confidence intervals.