Spatial redistribution of a globally constant marine biological carbon pump

Marine dissolved inorganic carbon (DICtotal) is a key component of the global ocean carbon cycle. Over recent decades, DIC has increased due to rising anthropogenic CO2, but the component of DIC change due to the biological carbon pump (BCP), which transfers carbon from the surface to the deep ocean, remains highly uncertain. Using the GOBAI-O2 data product and the CANYON-B and CONTENT algorithms, we reconstructed the 3-dimensional global DICtotal distribution from 2004 to 2022 and decomposed it into DICsoft (organic matter degradation), DICcarb (carbonate dissolution), and DICanth (anthropogenic CO2). We found a significant DICtotal change throughout the water column, with surface concentrations increasing by ~1.0 ± 0.23 μmol kg⁻¹ yr⁻¹, driven by DICanth (>90% contribution). Despite a globally constant signal in DICsoft, substantial regional trends emerged. Changes in circulation, particle sinking, and remineralization altered the vertical and horizontal distributions of DICsoft. In some regions, DICsoft accumulated at shallower depths, shortening residence times; in others, it was transported deeper, enhancing long-term storage. Although these widespread and divergent trends had little net effect on the global DICsoft inventory from 2004-2022, the emerging spatial reorganization of the BCP may signal an evolving instability in the ocean carbon sink under continued climate forcing.