Seasonal Variability of Surface Ocean Carbon Uptake and Chlorophyll-a Concentration in the West Antarctic Peninsula Over Two Decades

The Southern Ocean plays a vital role in global CO2 uptake, but the magnitude and even the sign of the flux remain uncertain, and the influence of phytoplankton phenology is underexplored. This study focuses on the West Antarctic Peninsula, a region experiencing rapid climate change, to examine shifts in seasonal carbon uptake. Using 20 years of in situ air-sea CO2 flux and satellite-derived Chlorophyll-a, we observe that the seasonal cycles of both air-sea CO2 flux and Chlorophyll-a intensify poleward. The amplitude of the seasonal cycle of the non-thermal component of surface ocean pCO2 increases with increasing latitude, while the amplitude of the thermal component remains relatively stable. Pronounced biological uptake occurs over the shelf in austral summer despite reduced CO2 solubility in warmer waters, which typically limits carbon uptake through physical processes. These findings underscore the prominence of biological mechanisms in regulating carbon fluxes in this rapidly changing region.