Regional characteristics of the temporal variability in the global particulate inorganic carbon inventory

Coccolithophores are a biogeochemically important calcifying group of phytoplankton that exert significant influence on the global carbon cycle. They can modulate the air-sea flux of CO2 through the opposing processes of photosynthesis and calcification, and as one of the primary contributors to the oceanic particulate inorganic carbon (PIC) pool, promote the export of organic carbon to depth. Here we present the first inter-annually resolved, global analysis of PIC standing stock. Average, global PIC standing stock in the top 100m is estimated to be 27.04 ± 4.33 Tg PIC, with turnover rates of ~7 days that suggest PIC is likely removed by active processes such as grazing or rapid sinking mediated through biogenic packaging (i.e., fecal pellets). We find that the southern hemisphere plays a significant role in the variability in PIC inventories and that inter-annual variability in PIC standing stock is driven primarily by variability in the mid-latitude oceanic gyres and regions within the Great Calcite Belt of the Southern Ocean. Our results provide a framework against which future changes in global PIC standing stocks may be assessed.