Intensification of Near-Inertial Currents in the Atlantic Ocean Over the Past Two Decades

Near-inertial currents (NICs) play a key role in surface material redistribution and ocean mixing, yet their long-term variability remains poorly known. Using in situ current measurements from surface drifters, we provide observational evidence for a pronounced intensification of surface NICs in the Atlantic Ocean over the past two decades (2003–2022). Basin–mean NIC strength increases at a rate of 3.8 ± 1.7% per decade, with a spatial pattern characterized by strengthening in the South Atlantic and the high-latitude North Atlantic, and weakening in the low-latitude North Atlantic. We further show that these trends in Atlantic NICs are primarily driven by changes in near-inertial wind forcing, particularly those associated with mesoscale weather systems, while variations in mixed-layer depth playing a minor role. This observed intensification of Atlantic NICs may have important implications for ocean transport and mixing, and needs to be properly represented in the current generation of climate models.