Mechanism of Atlantic Remote Influence on Pacific

Siying Liu, Ocean University of China, Oceanography, Qingdao, China, Ping Chang, Texas A&M University, Department of Oceanography, College Station, United States, Xiuquan Wan, Ocean University of China, Qingdao, China, Frederic S Castruccio, NSF National Center for Atmospheric Research, Boulder, United States, Stephen G Yeager, NCAR, Oceanography, Boulder, United States and Gokhan Danabasoglu, National Center for Atmospheric Research, Climate and Global Dynamics, Boulder, United States
Abstract:
El Niño-Southern Oscillation (ENSO) in the tropical Pacific plays a prominent role in global climate. Tropical trans-basin teleconnection can provide remote influence on ENSO development from other tropical basins. Previous Studies show anomalous warming in the North Atlantic can induce low-level cyclonic flow over the subtropical eastern Pacific as a Gill-type Rossby wave response that in turn affects ENSO development. Here, by conducting a large ensemble pacemaker experiment (140 runs) with the Community Earth system model (CESM1.1.2), we discover that diabatic heating (cooling) over the tropical north Atlantic can trigger ENSO cold (warm) events through a Gill-type Kelvin wave response. By applying a spectral analysis to outgoing longwave radiation (OLR) and equatorial wind fields, we find a significant increase of Kelvin wave activity in 10-30 day frequency band, which is consistent with baroclinic moist Kelvin waves. These atmospheric Kelvin waves propagate eastward from the Atlantic Ocean through the Indian Ocean and then to the Pacific Ocean, affecting equatorial thermocline in the eastern Pacific and exerting a remote influence on ENSO development.
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