HR: 0800h
AN: PP51A-0578    [Abstracts]
TI: Temperature and salinity changes in the Oyashio-Kuroshio mixed water region over the last 30 kyr
AU: * Sagawa, T
EM: sagawa@ees.hokudai.ac.jp
AF: Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, 060-0810 Japan
AU: Toyoda, K
EM: kazuhiro@ees.hokudai.ac.jp
AF: Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, 060-0810 Japan
AU: Oba, T
EM: oba-tad@ees.hokudai.ac.jp
AF: Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, 060-0810 Japan
AB: The Subarctic North Pacific has a strong halocline that prevents deep water coming up to the surface. Sedimentary data show low algal productivity in glacial time, implying increased polar ocean stratification (Sigman et al., 2004; Jaccard et al., 2005). Stable surface ocean stratification has a potential for controlling the atmospheric carbon dioxide concentration in glacial time. However, surface ocean salinity change in the Subarctic North Pacific is not known very much. If the water mass properties, such as temperature and salinity, have been changed in the Western Subarctic North Pacific, it must influence on the eastern coast of Japanese island via the Oyashio Current. We present Mg/Ca (a proxy for sea surface temperature) and δ¹⁸O record from planktonic foraminifera Globigerina bulloides in MD01-2420 (36.04_LdegN, 141.49_LdegE; 2101m) located off central Japan over the last 30 kyr. These data provide δ¹⁸O of seawater (δ¹⁸O_SW) and we used it for a proxy for past sea surface salinity. The reconstructed SST and δ¹⁸O_SW fluctuated synchronously resulting in alternation between cold, low-δ¹⁸O_SW and warm, high-δ¹⁸O_SW conditions. These fluctuations correspond to the Northern Hemispheric climate changes such as the Younger Dryas and Bolling-Allerod. Paired reconstruction of SST and δ¹⁸O_SW in MD01-2420 indicates that the surface salinity at the core site have been changed not only by the displacement of the Subarctic Front but also by the water mass properties change in the Oyashio Current. The δ¹⁸O_SW increase from 23 to 19 ka was presumably due to property changes in the Oyashio Current. The amplitude of the millennial-scale fluctuations in δ¹⁸O_SW was _Lsim0.5 permil. Using modern δ¹⁸O_SW vs salinity relationship, the δ¹⁸O_SW changes suggest _Lsim1.5 psu changes in salinity. These data imply that there is a possibility of the millennial-scale salinity changes occurred in the glacial Subarctic North Pacific.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4954 Sea surface temperature
DE: 9355 Pacific Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005