The role of mesoscale eddies as a possible energy source for diapycnal mixing in the deep ocean maintaining the global overturning circulation

2016 Fiscal Year Final Research Report

• Project/Area Number: 25800260
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: The University of Tokyo
• Principal Investigator: Tanaka Yuki 東京大学, 大学院理学系研究科(理学部), 助教 (80632380)
• Project Period (FY): 2013-04-01 – 2017-03-31
• Keywords: 鉛直乱流混合 / エネルギーフラックス / 内部波 / 風下波 / 熱帯不安定波 / 赤道太平洋 / 渦解像海洋大循環モデル

Outline of Final Research Achievements

Turbulent mixing in the thermocline of the equatorial Pacific Ocean is an important process that controls diapycnal heat transport and affects the global climate. In this study, using an eddy-resolving ocean general circulation model, we show that tropical instability waves (TIWs), propagating westward at a speed of ~0.5 m s-1 with a wavelength of ~1000 km, play an important role in inducing turbulent mixing. The front of the TIW is clearly manifested as a narrow strip of strong convergence of horizontal surface flow, from which area downward propagating internal waves are intermittently radiated. These internal waves can be interpreted as lee waves generated by the surface-flow convergence zone, which acts like an inverted obstacle moving along the ocean surface. The associated downward energy flux integrated over the entire equatorial Pacific averaged during January 2011 amounts to ~8.1 GW, creating an energy pathway to turbulent mixing in the thermocline of the equatorial Pacific.

Free Research Field

海洋物理学