Decadal trends in the oceanic storage of anthropogenic carbon

While we had already developed a global understanding of the oceanic accumulation of anthropogenic carbon (C_ant) over the industrial period, recent trends and decadal variability in this important sink remained largely unknown. Analysing three decades of ocean interior observations, Müller et al. (2023) reconstructed decadal storage changes in Cant between 1994 and 2014. Over the whole period, the ocean storage grew at an almost constant rate of ~28 PgC per decade. However, greater increases in atmospheric CO₂ from 2004 to 2014 indicate that ocean uptake in the recent decade was 15 ± 11% lower than expected based on the relationship between ocean uptake and atmospheric increase from the previous decade. The authors attribute this to both a decrease in the ocean buffer capacity and changes in ocean circulation. The latter is also reflected in the decadal variability of accumulation patterns that are most pronounced in the Atlantic Ocean. Furthermore, the global accumulation of C_ant was significantly different from the net surface fluxes of CO₂, suggesting substantial changes in the natural carbon inventory. These results emphasise the vulnerability of the ocean carbon sink to climate change.

Reference: Müller, J.D., Gruber, N., Carter, B., et al. (2023). Decadal trends in the oceanic storage of anthropogenic carbon from 1994 to 2014. AGU Adv., 4, e2023AV000875. https://doi.org/10.1029/2023AV000875