Dynamic Modes and Energy Pathways in the Changing Beaufort Gyre

Abstract The wind‐driven Beaufort Gyre is stabilized through frictional damping of momentum at topographic boundaries and eddy fluxes. Mesoscale eddies, located predominantly within the Beaufort Gyre's halocline stratification, contain most of its kinetic energy. The vertical distribution of kinetic energy is intrinsically linked to the Beaufort Gyre's stratification, which has changed significantly in recent decades in response to wind forcing. Notably, a prominent deepening of the lower halocline has been observed. We explore how these stratification changes affect dynamic mode structures and energy pathways (i.e., the exchange of energy between barotropic and baroclinic modes) in the Beaufort Gyre over 2003 to 2024. Triplet interaction coefficients, which are derived from the quasi‐geostrophic potential vorticity conservation equations, are used to quantify the efficiency of energy transfer between modes. We find that interactions within the second baroclinic mode (i.e., second mode velocity advecting second mode potential vorticity) are becoming increasingly efficient at keeping energy there, whereas interactions within the first baroclinic mode are becoming slightly less efficient. We couple our analysis of the interaction coefficients with an examination of mooring velocity data to determine how the modal distribution of kinetic energy has evolved over the past two decades. We find increased levels of kinetic energy concentrated in the first two baroclinic modes from 2019 to 2024, suggesting that the water column may be evolving to support a more active halocline eddy field as a balance on wind‐energy input. Our findings indicate that halocline eddies will likely play a greater role in stabilizing the Beaufort Gyre in the future.