Persistent ocean warming from 2023 to 2024 set another record in the South Pacific

With a sharp increase in the global surface temperature, the year 2023 witnessed an unprecedented level of marine heatwaves across the global ocean and record-breaking sea surface temperatures (SSTs) in multiple regions, including the Southwest Pacific. Updated observations indicate that the anomalous warming persisted and shifted eastward in the South Pacific from 2023 to 2024, resulting in record-high SST and upper-2000 m ocean heat content (OHC) in the south-central Pacific (SCP, 40°–60°S, 170°–110°W). SST warming was largely driven by net surface heat flux change mainly through the latent heat, with horizontal advection shaping the spatial pattern. Meanwhile, persistent OHC increase arose from two localized events of enhanced downwelling that transported heat into deeper layers up to 1000 m, occurring successively on the western and eastern sides of the SCP region in 2023 and 2024, driven by anticyclonic wind anomalies. Contrasts in SST, Antarctic sea ice, and atmospheric circulation between 2023 and 2024 reveal spatially coherent structures in the Southern Ocean that resemble the zonal wave 3 (ZW3), reinforcing anticyclonic wind anomalies over the SCP region. While the 2023/24 El Niño exhibited unusually weak teleconnections from the tropical Pacific, wave trains emanating from the tropical Indian Ocean seemed to play an important role in developing the anomalous ZW3-like patterns and phase shift. Understanding drivers and mechanisms of regional extremes is necessary for assessing frequency, predictability, and impacts of similar events in the coming years.