Tsubasa Kohyama , Hiroaki Miura, Shoichiro Kido

Observational records show that sea surface temperatures along the Gulf Stream and Kuroshio tend to synchronize at decadal time scales. This synchronization, which we refer to as the Boundary Current Synchronization (BCS), is reproduced in global climate models with high spatial resolution. Both in observations and model simulations, BCS is associated with meridional migrations of the atmospheric jet stream. Changes in the strength and path of the ocean currents driven by the jet shifts lead to the synchronicity of surface temperatures. Numerical simulations using a conceptual model and an atmospheric general circulation model are consistent with a notion that BCS is an interbasin air-sea coupled mode. The abnormally hot summer in 2018 over the Northern Hemispheric extratropics is explained by the positive phase of BCS.