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We have generated an oceanic primary production record from Core MD01-2421, off central Japan, in the western North Pacific, for the last 145,000 years, in order to examine how the Aleutian Low has responded to orbital-scale climate change. The variation of total organic carbon (TOC) was pronounced with a 41-ky periodicity. High TOC corresponds to a high angle of the Earth's obliquity. The variation of TOC was delayed behind the variation of obliquity by ∼ 1 ky and preceded the variation of δ18O of benthic foraminifera Uvigerina by ∼ 6 ky. The TOC varied inversely with Polar Circulation Index (Mayewski, P.A., Meeker, L.D., Twickler, M.S., Whitlow, S., Yang, Q., Lyons, B., Prentice, M., 1997. Major features and forcing of high-latitude northern hemisphere atmospheric circulation using a 110,000-year-long glaciochemical series. J. Geophys. Res. 102 (C12), 26345–26366.). Since the primary production in the Kuroshio–Oyashio mixed zone is related to the intensity of the winter Aleutian Low, these correspondences imply that the intensity of the winter Aleutian Low has responded to the obliquity forcing by the atmospheric reorganization in the northern high latitudes. The winter Aleutian Low was stronger when the obliquity was large, implying that the lower insolation in winter presumably increased the temperature contrast between the land and the ocean, deepening the winter Aleutian Low. |
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