| Autor: |
Naoto Takahata, Yuji Sano, Keika Horiguchi, Kotaro Shirai, Toshitaka Gamo |
| Předmět: |
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| Zdroj: |
Journal of Oceanography; Apr2008, Vol. 64 Issue 2, p293-301, 9p, 1 Diagram, 3 Charts, 5 Graphs, 1 Map |
| Abstrakt: |
Abstract We have collected fifty-five seawater samples at seven stations at various depths in the Yamato and Japan Basins of the Japan Sea and measured their helium isotopic ratios. The 3He/4He ratios vary from 0.997 Ratm to 1.085 Ratm where Ratm is the atmospheric ratio. The maximum 3He excesses about 8%, are observed at mid-depth (1000 m), and these values are significantly lower than those observed in deep Pacific waters. This implies that mantle-derived helium in deep Pacific water cannot enter the Japan Sea since it is an almost landlocked marginal sea. The observed 8% excess 3He may be attributable to the decay product of tritium. Slightly higher 3He/4He ratios in the Bottom Water were observed in the Yamato Basin than in the Japan Basin. The ventilation ages of seawater shallower than 1000 m are calculated as about 5 to 20 years, which is consistent with the CFC ages reported in the literature. There is a positive correlation between the apparent oxygen utilization and 3H-3He ages. The estimated oxygen utilization rate from the correlation in a layer between 500 m and 1000 m is about 3 µmol/kg/yr, which is similar to that in the eastern subtropical North Atlantic. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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