How has the recent decline in Antarctic sea ice contributed to the strengthening of the cooling trend near the Ross Sea gyre?

Despite the overwhelming warming over most oceans under global warming, cooling in the surface of the Southern Ocean between Australia and South America has been previously reported. The surface cooling is due to wind-driven sea-ice transport and its subsequent melting. However, Antarctic sea ice which has a steady increasing trend during several decades, experienced an abrupt decline to a record low in the mid-2010s. Since then, the interannual variability of Antarctic sea ice has been further intensified, showed another record low in 2022 and 2023 consecutively. Accordingly, the Pacific sector of the Southern Ocean has experienced warming during the period of rapid sea ice decline.

Nevertheless, we find that a coherent cooling pattern is observed in a very specific area, near the Ross Sea gyre. Here, to investigate the mechanisms associated with the cooling pattern, we examined how the rapid decline in Antarctic sea ice in recent years has contributed to the strengthening of the cooling trend near the Ross Sea gyre, using satellite observations of sea ice, as well as oceanic and atmospheric reanalysis data. Our result shows that the cooling trend has strengthened despite the rapid decrease in Antarctic sea ice in recent years. The significant cooling trend has been attributed to record atmospheric low pressure systems over the Pacific sector of the Southern Ocean. We demonstrate that the cooling near the Ross Sea gyre is likely influenced by the local and remote large-scale atmospheric variabilities that lead to substantial sea ice anomalies. Since the mid-2010s, local anomalous winds and surface heat flux associated with strong events of natural climate oscillations like the Zonal Wavenumber 3, El Niño–Southern Oscillation, and Southern Annular Mode in the Southern Hemisphere that drive the recent change in Antarctic sea ice, induce strong meridional flows led to enhanced sea ice drifts and melting, and consequently to the strong cooling trend.