17:15 〜 18:30
[MIS16-P05] Coral skeletal records reveal the relationship between Kuroshio variability and North Pacific climate
キーワード：サンゴ骨格、黒潮、窒素同位体比、酸素同位体比
The Kuroshio Current is a western boundary current in the North Pacific Ocean. The variations of its transport and migration under the global warming condition have been debated because they have a high impact on the climate, ecosystem, and fishery in the northwestern Pacific. Here, we reconstructed the Kuroshio transport variability and its migration over 70 years using coral skeletal records. Coral cores were collected from Tatsukushi Bay in 2008 on the Pacific coast of Japan, located on the northern front of the Kuroshio Current. Another coral cores were drilled at Cape Shionomisaki is located on the Kuroshio meander site.
The nitrogen isotope proxy in coral skeletons was used as a proxy to record the nitrogen isotope of nitrate controlled by the upwelling of subtropical subsurface water (+2−+3 permil), and coral nitrogen isotope was negatively correlated with observations of the Kuroshio transport (R = −0.69, P < 0.001) and the two years lagged PDO index (R = −0.63, P < 0.005) from 1972 to 2007. The 150-year record of coral nitrogen isotopes suggested that the Kuroshio transport varied with ~25-year cycle, and the amplitude became stable, and the volume was intensified through the twentieth century.
The Kuroshio transport was intensified with the La Nina state in the early 1900s and with the El Nino-PDO state after the 1920s. Our results suggested that the Kuroshio transport was influenced by the combined climate modes of ENSO and PDO during the last century. To detect the migration of Kuroshio, we used oxygen isotopes in dual coral cores at Cape Shionomisaki and Tatsukushi Bay. During 1930-2007, the maxima of the oxygen isotopes in the CS core correlated with the winter East China Sea temperature. However, the minima and maxima of the TB core's oxygen isotopes varied with salinity and temperature at the sea surface along the subtropical gyre. The oxygen isotope anomaly in the CS core from the TB core highlights cool and dry conditions with Kuroshio meander events. It correlated with Kuroshio meander's observational proxy, the tide level differences from Kushimoto to Urakami (R=+0.56, P<0.01).
The reconstructed Kuroshio migration suggested that Kuroshio migration is positively correlated with Kuroshio transport in an 8-12 year cycle. The axis of Kuroshio leaves Cape Shionomisaki with large transport. The Kuroshio meander events are not related to ENSO, but they have positive PDO mode. The coral skeletal archives in the northwestern Pacific can detect the transport and migration of Kuroshio currents.
The nitrogen isotope proxy in coral skeletons was used as a proxy to record the nitrogen isotope of nitrate controlled by the upwelling of subtropical subsurface water (+2−+3 permil), and coral nitrogen isotope was negatively correlated with observations of the Kuroshio transport (R = −0.69, P < 0.001) and the two years lagged PDO index (R = −0.63, P < 0.005) from 1972 to 2007. The 150-year record of coral nitrogen isotopes suggested that the Kuroshio transport varied with ~25-year cycle, and the amplitude became stable, and the volume was intensified through the twentieth century.
The Kuroshio transport was intensified with the La Nina state in the early 1900s and with the El Nino-PDO state after the 1920s. Our results suggested that the Kuroshio transport was influenced by the combined climate modes of ENSO and PDO during the last century. To detect the migration of Kuroshio, we used oxygen isotopes in dual coral cores at Cape Shionomisaki and Tatsukushi Bay. During 1930-2007, the maxima of the oxygen isotopes in the CS core correlated with the winter East China Sea temperature. However, the minima and maxima of the TB core's oxygen isotopes varied with salinity and temperature at the sea surface along the subtropical gyre. The oxygen isotope anomaly in the CS core from the TB core highlights cool and dry conditions with Kuroshio meander events. It correlated with Kuroshio meander's observational proxy, the tide level differences from Kushimoto to Urakami (R=+0.56, P<0.01).
The reconstructed Kuroshio migration suggested that Kuroshio migration is positively correlated with Kuroshio transport in an 8-12 year cycle. The axis of Kuroshio leaves Cape Shionomisaki with large transport. The Kuroshio meander events are not related to ENSO, but they have positive PDO mode. The coral skeletal archives in the northwestern Pacific can detect the transport and migration of Kuroshio currents.