Drivers of future seasonal and interannual changes in pCO2
To understand the mechanisms that control the pCO2 variability amplification we develop a complete analytical Taylor expansion of pCO2 in terms of its four drivers: DIC, T, total alkalinity (TA), and salinity (S). Using this linear approximation we show that the amplification is mainly caused by the increased response of pCO2 to T and DIC variations, due to a larger background pCO2 and a lower capacity to buffer DIC. However, there are large regional differences; the ocean's buffering capacity is reduced the most in the high latitudes, exposing them to larger pCO2 amplification rates. The DIC’s seasonal and interannual variations are projected to decrease in the equatorial Pacific, which counteracts the regional seasonal amplification and even reduces the future pCO2 interannual variability for some models. The intra-model differences in interannual projections indicate that the potential changes in water carbonate chemistry are simulated with higher consistency than those in ocean circulation and biology.