Synchronicity discovered in the Gulf Stream and Kuroshio
～A path to understanding extreme weather events caused by air-sea interaction～
Overview of the press release
We have discovered that, as the Gulf Stream and the Kuroshio Current (the strongest warm currents in the Northern Hemisphere) fluctuate, the sea surface temperatures off the east coast of Japan and the east coast of the U.S. are warmed and cooled synchronously. We refer to this phenomenon as the boundary current synchronization (BCS) (Fig.1).
Although these warm currents are separated by about 10,000 kilometers across the North American continent, they exchange information on the strength and paths of the currents through the north-south movement of the westerly jet stream - a strong westerly wind that exists over the mid-latitudes all year round - and synchronize their water temperatures. Heat waves brought about by this phenomenon, which target metropolitan areas in the mid-latitudes of the Northern Hemisphere, have been repeatedly observed, including in July of 1994 and 2018. The results of this research were published in the journal Science on 15 October 2021.
Figure 1: Schematic showing the mechanism of the boundary current synchronization (BCS).
The Gulf Stream and Kuroshio Current are synchronized, which is associated with the north-south movement of the atmospheric jet stream, causing near-surface temperatures to fluctuate. The red and blue shadings on the map show the temperature distribution near the Earth’s surface, which tends to be observed when both the Gulf Stream and Kuroshio Current are warmer than usual. A similar phenomenon is synchronization of pendulums. The metronome placed on a board suspended by strings transmits the information of directions and magnitude of the force to each other through the board, and the pendulum rods of the metronomes become eventually aligned. In BCS, the atmospheric jet stream plays a similar role to this board.
Associate Professor Hiroaki Miura (Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo.) contributed to this research.
To read the full press release, please visit the website of the Ochanomizu University.
Science（Vol. 374, Issue.6565, 15 October 2021）
TitleThe Gulf Stream and Kuroshio Current are synchronized Authors Tsubasa Kohyama, Yoko Yamagami, Hiroaki Miura, Shoichiro Kido, Hiroaki Tatebe, and Masahiro Watanabe DOI
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