1212 / 2024-09-20 16:50:20

Indian Ocean and Tropical Atlantic Drives Mid-Latitude Pacific Climate Changes

Indian Ocean, Tropical Atlantic, mid-latitude Pacific

Session 20 - Decadal Climate Variability: Key Processes of Air-Sea Interaction, Mechanisms and Predictability

Surface winds in the Pacific basin are pivotal in regional atmosphere-ocean interaction and global climate variability. Notably, during the satellite era, these surface winds have exhibited significant changes. While previous research predominantly concentrated on the intensified equatorial Pacific trade winds, their meridional extent has been less explored. This study uncovers that westward wind anomalies extend beyond the tropics into the mid-latitude Pacific, exhibiting substantial magnitudes of approximately 1 m/s, and significantly influencing sea surface temperature (SST) and sea level variations in the Pacific. Through a hierarchy of model simulations with different complexity, we demonstrate that the observed mid-latitude Pacific wind anomalies mainly stem from warming in the tropical Atlantic and Indian Oceans. This warming trigger stationary Rossby waves propagating into the Pacific, culminating in the formation of anomalous high-pressure centers over the mid-latitude Pacific. These centers, in turn, modulate surface winds in accordance with geostrophic balance, which further drives ocean warming over mid-latitudes Pacific. Our findings reveal a novel mechanism by which the tropical Atlantic and Indian Oceans exert a direct impact on the mid-latitude Pacific, thereby affecting atmosphere-ocean interactions, sea level dynamics in the Pacific basin, as well as the predictability and future projection of earth climate variability.