Abstract
Although knowledge of the past environments has been highly expected, there have been only few studies conducted on ocean environment exceed a century especially in the subtropical Northwestern Pacific due to a lack of observational data. Recently, however, two century-long coral records have become available, one is from Ishigaki Islands, southern Ryukyus (Mishima et al., in press) and the other is from Ogasawara Islands (Felis et al., 2009). Coral skeletal oxygen isotope data from Ishigaki showed a consistent profile with available sea surface temperature (SST) information for the post-1890s. The coral-based SST reconstruction enabled investigations on the relationships with the East Asian winter Monsoon (EAWM) and El Nino Southern Oscillation (ENSO). The Ishigaki coral record characteristically revealed the abrupt cooling during 1900-1905. This timing was consistent with exclusively cold winter in which Japan's lowest observational air temperature in 1902. It was suggested that development of Siberian High intensified the EAWM at this period. Also, it is probable that the cooling occurred in relation to the surface ocean freshening detected in the Ogasawara coral record in the early-twentieth-century [Felis et al., 2009]. Above consistency suggests the mutually coupled phenomenon uniquely found in the earliest 1900s in the northwestern subtropical Pacific.
References
Felis, T., A. Suzuki, H. Kuhnert, M. Dima, G. Lohmann, and H. Kawahata (2009), Subtropical coral reveals abrupt early-twentieth-century freshening in the western North Pacific Ocean, Geology, 37, 527-530, doi:10.1130/G25581A.1
Mishima, M., Suzuki, A., Nagao, M., Ishimura, T., Inoue, M., and Kawahata, H. Abrupt shift toward cooler condition in the Earliest 20th Century detected in a 165-year coral record from Ishigaki Island, southwestern Japan. Geophysical Research Letters, in press.
