지난빙하기부터 북서태평양 쿠로시오확장역의 경로변화

Abstract

The Kuroshio Extension (KE) refers to eastward-flowing inertial jet formed after the separation of Kuroshio Current from the Japanese coast flowing south of the Kuroshio Front (KF) with a few degree of latitudinal extent. The KE has migrated southward or northward in response to climate change over millennial to glacial/interglacial cycles. In order to understand latitudinal displacement of the Kuroshio Extension (KE) during the last 23 kyrs, oxygen isotope ratios (δ18O) of three planktic (G. ruber, N. incompta and G. inflata) and a benthic foraminifer species (Uvigerina spp.) were investigated with faunal assemblage of planktic foraminifera at a northwest Pacific site (32°16&#697 N, 158°13&#697 W, 2514 m depth) placed south of the meandering path of the KE. During the study period, differences of δ18O ratios between planktic and benthic foraminifers (Δδ18O) and between planktic species are relatively unchanging, suggesting the KF has remained to the north of the study site. In contrast, the relative proportions of N. dutertrei and N. incompta, the transitional to cold water species, have decreased gradually during the same period, accompanied by simultaneous increases of tropical and subtropical (G. ruber and G. sacculifer) and central water mass species (G. truncatulinoides). It suggests that the study site was under the frequent influence of the KE meanders during the LGM but the KE influence has graduallyd southward or northward in response to climate change over millennial to glacial/interglacial cycles. In order to understand latitudinal displacement of the Kuroshio Extension (KE) during the last 23 kyrs, oxygen isotope ratios (δ18O) of three planktic (G. ruber, N. incompta and G. inflata) and a benthic foraminifer species (Uvigerina spp.) were investigated with faunal assemblage of planktic foraminifera at a northwest Pacific site (32°16&#697 N, 158°13&#697 W, 2514 m depth) placed south of the meandering path of the KE. During the study period, differences of δ18O ratios between planktic and benthic foraminifers (Δδ18O) and between planktic species are relatively unchanging, suggesting the KF has remained to the north of the study site. In contrast, the relative proportions of N. dutertrei and N. incompta, the transitional to cold water species, have decreased gradually during the same period, accompanied by simultaneous increases of tropical and subtropical (G. ruber and G. sacculifer) and central water mass species (G. truncatulinoides). It suggests that the study site was under the frequent influence of the KE meanders during the LGM but the KE influence has gradually