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摘要
A hindcast of the Cs-137 concentration in seawater is conducted using a 0.5 degrees x 1 degrees global ocean general circulation model. A significant amount of Cs-137 concentration appears in the subtropical gyre in the South Pacific even though the source of Cs-137 is limited to the Northern Hemisphere. The pathway from the North Pacific to the South Pacific is examined using the Lagrangian approach. The Cs-137 in the South Pacific water is brought by the water that enters the equator through the interior pathway and the Mindanao Current from the subtropical gyre in the North Pacific. The water then flows along the Equatorial Undercurrent, and spreads to the South Pacific through the Ekman transports at the surface. A cross section of Cs-137 along 165 degrees E is examined by the Lagrangian approach and categorized based on the source region. The maximum Cs-137 concentration in 1975 comes from the formation region of the Eastern subtropical Mode Water (EMW) along the 24.7 sigma(0) surface, while the origin of the Cs-137 maximum in 2002 spreads over the Central Mode Water (CMW) and the Tropical Water (TW) along the 25.8 sigma(0) surface. The change of the maximum Cs-137 concentration from the water of EMW origin to the waters of CMW origin and TW origin is explained by the difference in the time evolution of Cs-137 in the ventilated region. The Cs-137 concentration decreases much more slowly in the formation regions of CMW and TW than in that of EMW.
- 出版日期2010-6-22
- 单位中国气象科学研究院
