Study on oceanic thermocline structure in subtropical/subpolar gyres

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10640414
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: HOKKAIDO UNIVERSITY
• Principal Investigator: KUBOKAWA Atsushi Hokkaido Univ., Grad. School of Env. Earth Sci., Pro., 大学院・地球環境科学研究科, 教授 (00178039)
• Project Period (FY): 1998 – 1999
• Keywords: Ocean circulation / Thermocline / Eastern boundary ventilation / Cross-gyre flow / Oceanic response / Planetary waves / Ventilated thermocline theory

Research Abstract

Numerical experiments with idealized OGCM were carried out to investigate the oceanic eastern boundary structure and its effects on the thermocline structure. The experimental results indicate that the zonal flow in the vicinity of the eastern boundary is limited in the mixed-layer, which is realized by the density gap just above the thermocline. Diapycnal process does not act an important role at the eastern edge of the basin except in the mixed layer. Formulation for the eastern boundary structure is also presented. It was also shown that such eastern boundary structure strongly affects the thermocline in the interior region. On the shallow thermocline in the subtropics, eastern boundary ventilated region is emerged, which is identified as a region of high potential vorticity. In the deep thermocline, which does not outcrop in the subtropical, a cross-gyre ventilation occurs. This cross-gyre ventilation is caused by the density structure at the eastern boundary.
In addition to the above work, we carried out theoretical studies on the response of oceanic thermocline to enhancement of Ekman pumping velocity, and on the planetary wave dynamics in 2.5-layer ventilated thermocline model.