[대기] [초청세미나] 강사라 교수(Max Planck Institute)
일시 : 2026-07-29(수) 13:30 ~ 14:30
연사 : 강사라 교수
소속 : Climate Dynamics, Max Planck Institute
문의 :
장소 : 501동 1층 목암홀
Title: Beyond Bjerknes: Southern Ocean and Land Controls on the Tropical Pacific
Abstract: The observed sea-surface temperature trend exhibits a La Niña-like pattern, in contrast to the El Niño-like GHG-driven response simulated by most CMIP-class models. Whether this discrepancy reflects internal variability, missing forced mechanisms, or model biases remains unclear. Here, we examine two potential drivers of the observed tropical Pacific warming pattern: Southern Ocean cooling and land warming.
Coupled-model experiments show that imposing the observed Southern Ocean cooling produces cooling in the southeastern tropical Pacific, implicating a Southern Ocean–tropical Pacific teleconnection. Kilometer-scale ICON historical simulations, which explicitly resolve mesoscale ocean eddies, reproduce cooling in both the Southern Ocean and eastern tropical Pacific, highlighting the importance of ocean eddies in shaping the global SST trend pattern.
We then show that the CO₂-forced response can initially be La Niña-like because land warms faster than the ocean. Regional land-only CO₂ experiments reveal that this response is mediated by a northward ITCZ shift, intensification of the South Pacific subtropical high, and an eastward extension of warm-pool convection. These findings further motivate a new hypothesis for the origin of the climatological Walker circulation: the Americas anchor its eastern, subsiding branch and thereby organize the tropical Pacific zonal circulation. This view contrasts with the conventional framework in which ocean upwelling and the Bjerknes feedback are regarded as the fundamental drivers of the Walker circulation.
Abstract: The observed sea-surface temperature trend exhibits a La Niña-like pattern, in contrast to the El Niño-like GHG-driven response simulated by most CMIP-class models. Whether this discrepancy reflects internal variability, missing forced mechanisms, or model biases remains unclear. Here, we examine two potential drivers of the observed tropical Pacific warming pattern: Southern Ocean cooling and land warming.
Coupled-model experiments show that imposing the observed Southern Ocean cooling produces cooling in the southeastern tropical Pacific, implicating a Southern Ocean–tropical Pacific teleconnection. Kilometer-scale ICON historical simulations, which explicitly resolve mesoscale ocean eddies, reproduce cooling in both the Southern Ocean and eastern tropical Pacific, highlighting the importance of ocean eddies in shaping the global SST trend pattern.
We then show that the CO₂-forced response can initially be La Niña-like because land warms faster than the ocean. Regional land-only CO₂ experiments reveal that this response is mediated by a northward ITCZ shift, intensification of the South Pacific subtropical high, and an eastward extension of warm-pool convection. These findings further motivate a new hypothesis for the origin of the climatological Walker circulation: the Americas anchor its eastern, subsiding branch and thereby organize the tropical Pacific zonal circulation. This view contrasts with the conventional framework in which ocean upwelling and the Bjerknes feedback are regarded as the fundamental drivers of the Walker circulation.
