Intensification of near-inertial currents in the Atlantic Ocean over the past two decades

Abstract

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. Ocean drifter observations reveal that Atlantic near-inertial currents intensified by almost 4% per decade during 2003–2022. This intensification is primarily driven by changes in wind forcing associated with mesoscale weather systems.