Impacts of Stratospheric Ozone on Antarctic Spring Sea Ice: Based on WACCM6

Austral spring (September–November) represents the season with the most pronounced chemical depletion of stratospheric ozone over Antarctica, during which the associated radiative and circulation responses reach their annual maximum. Against the background of persistently low Antarctic sea ice, this study focuses on austral spring and examines the influence of stratospheric ozone variability on Antarctic sea ice through both thermodynamic and dynamic processes. The analysis is based on simulations from the Whole Atmosphere Community Climate Model version 6 (WACCM6), combined with composite analysis and other statistical methods, to investigate the interannual variability of Antarctic springtime stratospheric ozone and its impacts on sea ice.The results indicate that WACCM6 successfully reproduces the interannual variability of Antarctic spring total column ozone (TCO), with simulated TCO variations consistent with those derived from the SWOOSH and Microwave Limb Sounder (MLS) observational datasets. Composite analyses show that ozone-related anomalies in Antarctic spring sea ice concentration are primarily confined to the seasonal ice zone between 60°S and 70°S, with magnitudes reaching ±5%–20%. During years of anomalously high springtime stratospheric ozone, sea ice concentration over the Amundsen and Bellingshausen Seas (ABS; 60°S–70°S) exhibits significant negative anomalies, indicating a marked reduction of sea ice along the ice-edge region. Thermodynamic analysis reveals that elevated springtime stratospheric ozone is associated with pronounced positive anomalies in sea surface temperature and surface net radiation over the ABS ice-edge zone, with magnitudes of approximately +1–3 °C and +5–15 W m⁻², respectively. The enhanced radiative heating leads to substantial near-surface warming, thereby suppressing sea ice formation and accelerating ice-edge melt. Further analysis of the dynamical processes shows that increased absorption of shortwave radiation by ozone induces warming in the high-latitude stratosphere, accompanied by rising geopotential heights and a weakened meridional temperature gradient. As a result, high-latitude stratospheric westerlies weaken and the polar vortex intensity decreases. These stratospheric circulation anomalies subsequently propagate downward and modify near-surface wind stress patterns, creating wind forcing favorable for Ekman pumping in the ice-edge region. The enhanced upwelling of subsurface warm water ultimately contributes to reduced sea ice concentration along the Antarctic seasonal ice zone.