Wind Power on Oceanic Near‐Inertial Oscillations in the Global Ocean Estimated From Surface Drifters.

Wind power on oceanic near‐inertial oscillations is thought to play an important role in furnishing the diapycnal mixing in the ocean. Yet their global distribution and magnitude have not been quantified based on observations. In this study, we use hourly ocean current records derived from surface drifters to compute the global near‐inertial wind power during 1993–2016, with a combination of surface wind measurements obtained from satellites. The climatological near‐inertial wind power integrated between 60°S and 60°N is estimated to be 0.3–0.6 TW. The strongest energy flux occurs in the 30–60° latitude band during the winter season as a result of energetic storm activities. Ocean current imprint on wind stress has a significant impact on the estimated global near‐inertial wind power from drifters. Neglecting this imprint overestimates the near‐inertial wind power locally by 25–120% and its global mean value by 60%. Plain Language Summary: Wind stress fluctuations in the near‐inertial band can resonantly force near‐inertial oscillations (NIOs) in the surface mixed layer. These wind‐generated NIOs radiate downwards into the ocean interior, transfer their energy to small scales, and eventually break, providing energy to furnish the diapycnal turbulent mixing in the thermocline and deep ocean. In the past two decades, the global near‐inertial wind power has been extensively studied based on numerical models. However, the estimated values differ significantly (0.3–1.5 TW) among studies. Such a great range throws doubts on the validity of the model simulated near‐inertial wind power. It also causes uncertainties in the contribution of NIOs to diapycnal turbulent mixing and their parametrizations in ocean general circulation models. Therefore, it is essential to obtain a benchmark for global near‐inertial wind power based on observations. In this study, we evaluate the global near‐inertial wind power based on drifters and satellite‐measured winds. The climatological near‐inertial wind power integrated between 60°S and 60°N is estimated to be 0.3–0.6 TW. It is found that the ocean current imprint on wind stress has a significant impact on the estimated near‐inertial wind power. Neglecting this imprint leads to overestimation of near‐inertial wind power globally by 60% and locally by 25–120%. Key Points: The climatological near‐inertial wind power integrated between 60 degrees south and 60 degrees north is estimated to be 0.3‐0.6 TWNeglecting ocean current imprint on wind stress overestimates the near‐inertial wind power [ABSTRACT FROM AUTHOR]