Variability of the path of the Kuroshio ocean current over the past 25,000 years

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The Kuroshio current is the strong northwestern component of the subtropical North Pacific Ocean gyre, and advects a large amount of heat from the tropics to northern mid-latitudes. The Kuroshio has bimodal stationary flow patterns, with small and large meander paths east of central Japan [1,2] which switch on annual and decadal timescales [3,4]. These switches seem to be caused by changes in current velocity and volume transport of the North Equatorial Current that are associated with variations in the trade-wind intensity in the eastern equatorial North Pacific Ocean [5,6]. Here we present alkenone-derived sea surface temperature records at multicentennial resolution from sediment cores from the Nishishichitou ridge off central Japan. These 25,000-year records show that the Kuroshio path has also fluctuated on millennial timescales. This variability resembles that of the subtropical high pressure of the North Pacific, reconstructed from terrestrial pollen distributions, water levels in North American lakes, and marine micropalaeontological records [7]. Together, these data indicate that climate variability off central Japan over the past 25,000 years may be part of a circum-Pacific phenomenon, reflecting the rate of subtropical surface circulation in the North Pacific Ocean.

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