Accelerated internal tides in a warming climate

Internal tides profoundly influence diapycnal mixing and marine ecosystems in oceans worldwide. Previous estimates on internal tides focused regionally spanning a decade, leaving a knowledge gap regarding their long-term global behavior, especially over centuries. Because of limited long-term observations, a critical question arises: How will global warming affect internal tides? Using the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the High-Resolution Empirical Tidal (HRET) model, we identify a robust accelerating trend in globally averaged internal tide speeds. This trend, increasing from historical rates (0.4 centimeters per second per decade) to future projections (2.0 centimeters per second per decade), is primarily driven by intensified upper-ocean stratification, with background currents playing a secondary role. Our findings suggest that internal tides propagate faster in a warming climate, potentially influencing energy cascade and marine biological productivity.