Tropical Atlantic and Indian Ocean Warming Impact on the Subtropical High and Aleutian Low

Due to its active role in the atmosphere-ocean interactions and in the global and regional climate variability, the sub-tropical high and the Aleutian Low over the Pacific Ocean has been receiving increased attention. In the past three decades, the sub-tropical high has been intensified and shifted poleward. Meanwhile the Aleutian Low has been dramatically weakened. These changes have immediate impact on the climate variability over the Asian and the North America. The associated wind changes can contribute to the observed sea surface temperature (SST) changes in both tropical and mid-latitude Pacific. However, the mechanisms of the changes in the sub-tropical high and the Aleutian Low remain unclear. To untangle this problem, we combine observations, reanalysis datasets, and a hierarchy of climate model simulations. Analysis based on measurements and reanalysis datasets show that the changes in sub-tropical highs and Aleutian Low become are not driven by the regional Pacific SST changes. Instead, the circulation changes are mostly caused by remote influences originated from the tropical Atlantic and Indian Ocean SST changes through stationary Rossby waves. This finding builds a direct pathway linking the tropical Atlantic and Indian Ocean to the mid-latitude Pacific. This pathway has a broad implication for understanding air-sea interactions and sea level changes over the Pacific, and may have an important impact on the interannual and decadal predictability of the Pacific climate variability, such as Pacific Decadal Oscillation and El Niño – Southern Oscillation.