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202412202412
Silicoflagellate assemblages in the North Pacific surface sediments: an application of the modern analog method to reconstruct the glacial sea surface temperature in the Japan Sea
Okazaki Y, Onodera J, Tanizaki K, Nishizono F, Egashira K, Tomokawa A, Sagawa T, Horikawa K, Ikehara KYusuke Okazaki, Jonaotaro Onodera, Kyohei Tanizaki, Fumiaki Nishizono, Kazuki Egashira, Asuka Tomokawa, Takuya Sagawa, Keiji Horikawa, Ken Ikehara
Silicoflagellates, North Pacific, Japan Sea, Sea surface temperature, Modern analog method, Last Glacial Maximum, Tsushima Warm Current
（Left）Geographic distribution of silicoflagellate species, Dictyocha messanensis in the North Pacific (relative abundances, %). (Right) Silicoflagellate-based annual-mean sea-surface temperature reconstruction for Core KR15-10 WB6 in the southern Japan Sea (red line with confidence regions with 68.2% (light green) and 95.4% (green) since ~26 ka ago.
Recent silicoflagellate distributions have been examined in 195 surface sediment samples from the North Pacific to establish the silicoflagellate assemblage dataset from surface sediments across the North Pacific for paleo sea surface temperature (SST) reconstruction. The relative abundance data of all seven silicoflagellate taxa identified in this study were used for the modern analog method to reconstruct past SST. The SST reconstruction based on the silicoflagellate modern analog technique was applied to the two sediment cores from the Japan Sea. With the development of ice sheets, the Japan Sea experienced a low salinity isolation event during the Last Glacial Maximum (LGM: 19 ka–26.5 ka), which hampers the SST reconstruction employing geochemical proxies such as alkenone and Mg/Ca thermometry. The reconstructed glacial SST between 25 and 15 ka was ~ 5 °C in the northern and southern Japan Sea, indicating significant southward migration of the glacial subpolar front. The timings of the deglacial SST rises were ~ 14 ka at the south core site and ~ 10 ka at the north core site, indicating a latitudinal lag. This lag likely reflects a gradual increase in the fluxes of the Tsushima Warm Current from the East China Sea through the Tsushima Strait. Compilation of the silicoflagellate assemblages in the North Pacific surface sediments used for the modern analog technique to reconstruct past sea surface temperature (SST), revealing the Japan Sea SST during the last glacial maximum ~20 ka ago.
