Robust Warming Hole in the Southeast Pacific

Understanding CO₂-induced surface warming patterns is essential for regional climate projections. Abrupt 4×CO2 experiments reveal well-documented warming holes in the subpolar North Atlantic (NA) and Southern Ocean (SO), yet a similarly robust but less recognized warming hole emerges in the Southeast Pacific (SEP). Unlike the warming holes over NA and SO, which disappear in slab ocean models without active ocean circulation, the SEP warming hole persists and intensifies, indicating the dominant role of air–sea interactions. Latitudinally constrained CO₂ forcing experiments demonstrate that off-equatorial Northern Hemisphere (NH) forcing drives the SEP warming hole by inducing an interhemispheric energy imbalance, shifting the Hadley circulation (HC) northward, and strengthening the Southern Hemisphere subtropical descent. This enhances the South Pacific Subtropical High and the associated southeasterly trade winds. Combined with a stronger cross-equatorial flow associated with the northward-shifted HC, the enhanced winds contribute to the SEP warming hole through increased latent heat flux. Inter-model spread of SEP warming hole across CMIP6 models is well explained by variations in wind-driven latent heat flux, primarily controlled by cloud-mediated interhemispheric energy asymmetry. These results identify atmospheric teleconnections as the key driver of the SEP warming hole, distinguishing it from the ocean-driven mechanisms in the NA and SO.