Work

Ongoing intensification of anomalous Western North Pacific anticyclone during post-El Niño summer with achieved carbon neutrality

Year: 2024

Type: article

Abstract: A notable anomalous lower-tropospheric anticyclone appears over the western North Pacific (WNP) during post-El Niño summer, exerting a profound influence on the East Asia summertime climate. Here, we employ a suite of global climate model projections under symmetric CO2 ramp-up (RU) and ramp-down (RD) scenarios to reveal the asymmetric response of the WNP anticyclone (WNPAC). Our results demonstrate a progressive strengthening of the WNPAC with rising CO2 concentrations, a trend that persists as CO2 declines, followed by gradual recovery, and the anomalous anticyclone fails to return to its initial state when CO2 concentrations return to pre-industrial levels, attributed to Indo-Pacific zonal SST gradient variations. In contrast to the CO2 RU phase, the increased zonal SST gradient is witnessed in the CO2 RD phase, favoring anomalous moisture convergence over the Maritime Continent (MC). This strengthens the WNPAC through Kelvin wave-induced Ekman divergence or local Hadley circulation adjustment. The increased zonal SST gradient is associated with strengthened SST warming in the MC and accelerated decay of El Niño-related positive SST anomalies in the equatorial Central Pacific, ultimately attributed to a climatological equatorial Pacific El Niño-like warming pattern driving intricate air-sea interactions and processes. Our findings indicate that the overshoot of the WNPAC during the CO2 RD phase may exacerbate the flood and high temperature risks in densely populated East Asia.

Source: npj Climate and Atmospheric Science

DOI: 10.1038/s41612-024-00871-3