Increased Carbon Sink Within the Seasonal Sea Ice Zone Associated With Climate Variability in the Southern Ocean

Abstract Ice distributions in Antarctica have undergone substantial changes over the past few decades, notably characterized by a progressive expansion of the seasonal sea ice zone (SIZ). However, the carbon sink dynamics and mechanisms in this climate‐sensitive region remain uncertain. We applied a random forest algorithm on satellite data to reconstruct a 20‐year (2003–2022) record of spring‐summer CO 2 flux in the Southern Ocean. Our findings revealed that the rate of CO 2 uptake increase in the SIZ is nearly four times faster than that in the non‐SIZ, suggesting a notable poleward shift of Southern Ocean carbon sink. The accumulation of the SIZ carbon sink was attributed to enhanced phytoplankton growth during austral spring‐summer, driven by the positive trend of the Southern Annular Mode. These results deepen understanding of the intricate relationship between climate variability and regional carbon sink dynamics, offering valuable insights into future climate change impacts on polar carbon sinks.