Jet Stream Variability and Ocean–Atmosphere Forcing in Driving Sea Ice Extremes in the Ross Sea, Winter 2023

The decline of sea ice in polar regions is a critical environmental concern, indicating broader climate change impacts. The Ross Sea experienced its lowest annual ice maximum (3.47 × 10 6 km 2 ) on 14 September, following an unusual ice retreat during winter 2023. From 27 July to 6 September, the ice extent remained at record low levels, reaching ~3.5 standard deviations below the long‐term average (1981–2010). The decrease in sea ice occurred against a background of remarkable environmental changes driven by atmospheric circulation anomalies associated with the strengthening of an atmospheric split jet, along with persistent ocean warming. In winter 2023, a strong north‐westerly flow from the subpolar branch of the jet extended southward to form a robust polar front jet that shifted ~1460 km, reaching as far south as 73° S, compared to its usual position at 60° S. The splitting of this jet stream and its meandering manifested as an atmospheric blocking system that remained stationary over the Ross Sea, significantly contributing to the reduction in ice extent. These changes in the atmospheric circulation are linked to the Pacific South American wave pattern associated with the Rossby wave train. This indicates the role of El Niño Southern Oscillation and Indian Ocean Dipole in modulating the atmospheric circulation anomalies over the Ross Sea.