Away from boundaries, turbulent diapycnal mixing is dominated by the breaking of internal waves. To maintain the large-scale oceanic conveyor belt and the existing structure of marine stratification, an energy source of 2 TW is needed to furnish the turbulent diapycnal mixing below the main thermocline in the open ocean ( Munk and Wunsch 1998 Wunsch and Ferrari 2004 St. 2009 Marshall and Speer 2012 Oka and Niwa 2013). Its variability influences the global ocean heat uptake and biological carbon storage, playing a fundamental role in climate change ( Broecker 1991 Mikaloff Fletcher et al. The global ocean conveyor belt is a constantly circulating system of ocean currents that transport water and redistribute heat and carbon around the world. The quasi-global integral of energy transfer below the SBL base is two orders of magnitude smaller than that of F SBL, suggesting the resolved BMs in the CESM simulations making negligible contributions to power NIWs in the ocean interior. The kinetic energy transfer from model-resolved BMs to NIWs is positive from the SBL base to 600 m but becomes negative farther downward. It exhibits an increasing trend with the enstrophy of balanced motions (BMs) and a decreasing trend with W I. The ratio of local F SBL to W I varies substantially over the space. Its quasi-global integral (excluding the region within 5°S–5°N) is 0.13 TW, about one-third the value of W I. ![]() The simulated downward flux of NIW energy ( F SBL) at the SBL base is positive everywhere. ![]() The CESM shows good skill in simulating NIWs globally, reproducing the observed magnitude and spatial pattern of surface NIW currents and wind power on NIWs ( W I). This key problem is addressed in this study based on a Community Earth System Model (CESM) simulation with a horizontal resolution of ~0.1° for its oceanic component and ~0.25° for its atmospheric component. Nevertheless, the energy flux into NIWs below the surface boundary layer (SBL) in the global ocean is still poorly understood. Near-inertial internal waves (NIWs) are thought to play an important role in powering the turbulent diapycnal mixing in the ocean interior.
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