Fig. 1: Ocean CO₂ sink constrained at global scale and by latitude bands between 1990 and 2022.

Positive values denote a sink for CO₂. a The global ocean is divided into three latitudinal bands: b North (>30°N), c Tropics (30°N–30°S), and d South (<30°S). The thick black line represents NEMO-PlankTOM12.1 standard simulation, the thin black lines represent the perturbed simulations, and the red dots represent the estimate using the hybrid approach with ±1σ (68%) confidence interval. On the x axis, the years highlighted in red have an unconstrained ocean CO₂ sink. Empty red dots are years with an ocean CO₂ sink value constrained but outside the bounds of the perturbation experiments (i.e., uncertain values, see methods). The perturbed simulations are produced by varying the half-saturation constant of bacterial remineralisation (from 5 × 10⁻⁶ mol L⁻¹ to 18 × 10⁻⁶ mol L⁻¹).