Wind Damping of Internal Tides in the Global Ocean

Internal tides (ITs) play a fundamental role in ocean dynamics by transferring tidal energy through cascades to small-scale turbulence, ultimately driving diapycnal mixing that sustains the deep-ocean circulation and regulates biogeochemical cycles. While ITs energy sinks are traditionally attributed to topographic interactions, the impact of surface wind forcing on this energy pathway remains a significant area of uncertainty. To address this knowledge gap, this study employs a dynamical decomposition approach applied to realistic ITs-resolving numerical simulations to quantify the wind impact on ITs in the global ocean. Our analysis reveals that wind forcing globally imposes a strong damping effect on ITs, with a median magnitude of the wind work on ITs of O (10^-4)  W/m². Globally, this wind damping accounts for a non-negligible fraction of the total ITs energy sink, substantially influencing the distributions of ITs and the diapycnal mixing they induce. To provide observational constraints beyond numerical simulations, we develop a scaling approach to estimate wind damping of ITs by projecting the ITs velocity onto the wind direction and evaluating the net wind work over a tidal cycle. Our findings collectively suggest that wind damping constitutes a critical component of the ITs energy budget. This challenges the conventional paradigm of predominantly topography-driven energy sinks and underscores the necessity of integrating atmospheric forcing into a holistic understanding of ITs energy budget.