By P Gosselin
A new paper titled “The recent zonal asymmetry of temperature change in the Antarctic circumpolar current” published in Climate Dynamics, March 2026 by XuBin Ni, Ling Du, HuangYuan Shi, and YiYong Luo) investigates regional temperature trends within the Antarctic Circumpolar Current (ACC) and highlights a distinct zonal (longitude-based) asymmetry in how the Southern Ocean responds to global climate change after 2005.
uniformly, post-2005 temperature trends across the ACC display a striking geographic split:
1.) The South Pacific Sector (60∘ W to 180∘) exhibits an unexpected and significant cooling trend reaching up to −0.4∘C per decade, penetrating deep into the intermediate ocean.
2) The South Atlantic and Indian Sectors: Simultaneously exhibit persistent and significant warming.
The authors claim that this regional asymmetry is primarily governed by changes in ageostrophic advection (ocean transport not strictly in geostrophic balance), which are modulated by the combined interactions of zonal winds (westerlies) and surface buoyancy fluxes.
The cooling in the South Pacific is driven by two main factors:
1.) Intensified westerly-driven cold water supply (equatorward Ekman transport).
2) Enhanced buoyancy loss, which drives deep cooling penetrating into the intermediate ocean layers.
Net ageostrophic advection accounts for −148.7 TW, explaining roughly 75% of the observed Pacific cooling.
Causes of Atlantic and Indian sector warming:
Conversely, the warming in the Atlantic and Indian sectors is primarily driven by poleward warm water intrusions originating from the subtropical ocean, alongside buoyancy gains that trap surface cold water locally within the mixed layer. Net ageostrophic advection contributes +75.0 TW to this warming trend.
CO2 is not the main driver of climate dynamics. The chaotic, poorly understood grand system is subject a complex web of interwoven factors that cannot be boiled down to a single trace gas.
