Kubota Yoshimi, Haneda Yuki, Kameo Koji, Itaki Takuya, Hayashi Hiroki, Shikoku Kizuku, Izumi Kentaro, Head Martin J, Suganuma Yusuke, Okada Makoto
Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1, Amakubo, Tsukuba, Ibaraki, 305-0005 Japan.
Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8567 Japan.
Prog Earth Planet Sci. 2021;8(1):29. doi: 10.1186/s40645-020-00395-3. Epub 2021 Apr 30.
The fluctuating position of the boundary between the Kuroshio (warm) and Oyashio (cold) currents in the mid-latitude western North Pacific affects both heat transport and air-ocean interactions and has significant consequences for the East Asian climate. We reconstruct the paleoceanography of Marine Isotope Stages (MIS) 20-18, MIS 19 being one of the closest astronomical analogues to the present interglacial, through multiple proxies including microfossil assemblage data, planktonic foraminiferal isotopes (δO and δC), and foraminiferal Mg/Ca-based temperature records, from the Chiba composite section (CbCS) exposed on the Boso Peninsula, east-central Japan. Principal component analysis (PCA) is used to capture dominant patterns of the temporal variation in these marine records, and shows that the relative abundances of calcareous nannofossil and radiolarian taxa are consistent with the water mass types inferred from geochemical proxies. The leading mode (36.3% of total variance) mirrors variation in the terrestrial East Asian winter monsoon (EAWM), reflecting seasonal trends dominated by the winter monsoon system. In the CbCS, this mode is interpreted as reflecting the interplay between the warm Kuroshio and cold Oyashio waters, which is likely related to the latitudinal shift of the subtropical-subarctic gyre boundary in the North Pacific. The second mode (15.4% of total variance) is closely related to subsurface conditions. The leading mode indicates that MIS 19b and 19a are represented by millennial-scale stadial/interstadial oscillations. Northerly positions for the gyre boundary during late MIS 19c, the interstadials of MIS 19a, and early MIS 18 are inferred from the leading mode, which is consistent with a weak EAWM and consequent mild winter climate in East Asia. Nonetheless, the northerly positions for the gyre boundary during late MIS 19c and early MIS 19a were not associated with subsurface warming presumably due to the suppressed gyre circulation itself caused by the weak Aleutian Low. Intermittent southerly positions for the gyre boundary are inferred for the stadials of MIS 19b and 19a. Regional sea surface temperature (SST) comparisons in the western North Pacific reveal that the moderate SSTs during MIS 19a through early MIS 18 were restricted to the mid- to high latitudes, influenced by the weak EAWM. Comparison between MIS 20-18 and MIS 2-1 suggests that glacial MIS 20 and 18 had significantly milder winters than MIS 2, likely related to the relatively weak EAWM.
The online version contains supplementary material available at 10.1186/s40645-020-00395-3.
黑潮（暖流）和亲潮（寒流）在北太平洋西部中纬度地区的边界位置波动，影响着热量输送和气 - 海相互作用，对东亚气候有着重大影响。我们通过多种代理指标，包括微化石组合数据、浮游有孔虫同位素（δO和δC）以及基于有孔虫Mg/Ca的温度记录，从日本中东部房总半岛暴露的千叶复合剖面（CbCS）重建了海洋同位素阶段（MIS）20 - 18的古海洋学，MIS 19是与当前间冰期最接近的天文类似物之一。主成分分析（PCA）用于捕捉这些海洋记录中时间变化的主导模式，结果表明钙质超微化石和放射虫类群的相对丰度与地球化学代理指标推断的水体类型一致。主导模式（占总方差的36.3%）反映了东亚冬季风（EAWM）在陆地上的变化，体现了以冬季风系统为主导的季节趋势。在CbCS中，这种模式被解释为反映了温暖的黑潮和亲潮冷水之间的相互作用，这可能与北太平洋亚热带 - 亚北极环流边界的纬度移动有关。第二种模式（占总方差的15.4%）与次表层状况密切相关。主导模式表明MIS 19b和19a以千年尺度的冰期/间冰期振荡为特征。从主导模式推断出MIS 19c晚期、MIS 19a间冰期和MIS 18早期环流边界的偏北位置，这与东亚冬季风较弱以及随之而来的温和冬季气候一致。然而，MIS 19c晚期和MIS 19a早期环流边界的偏北位置与次表层变暖无关，可能是由于阿留申低压减弱导致环流本身受到抑制。推断出MIS 19b和19a冰期环流边界的间歇性偏南位置。北太平洋西部区域海表温度（SST）比较显示，MIS 19a至MIS 18早期的中等海表温度受东亚冬季风较弱的影响，局限于中高纬度地区。MIS 20 - 18与MIS 2 - 1的比较表明，冰川期的MIS 20和18冬季比MIS 2明显温和，可能与相对较弱的东亚冬季风有关。
在线版本包含可在10.1186/s40645 - 020 - 00395 - 3获取的补充材料。
