Tracing vortex trajectories reveals how resources are exchanged between oceans

The Lofoten Basin, in the Norwegian Sea, has an annually recurring anticyclonic vortex at its center, which mixes water and salt between the Atlantic and Arctic oceans. Vortices like these have large-scale influences on ocean circulation and climate variability, and the Lofoten Vortex’s longevity offers a natural laboratory for studying how eddies affect climate dynamics over long periods of time.

By quantifying rotations of markers, known as tracers, around the eddy center, Novoselova et al. developed a new method — which they call the Lagrangian Eddy Boundary Delineation Algorithm (LEBDA) — to define a physically meaningful eddy boundary. They applied this approach to existing data of the Lofoten Vortex to uncover a range of previously inaccessible behaviors.

“The periphery of an oceanic eddy is dynamically complex, fractal, and highly heterogeneous, and … this complexity fundamentally controls how water, heat, and tracers are exchanged between the eddy and the surrounding ocean,” said author Tatyana Belonenko. “LEBDA makes this complexity visible and quantifiable.”

A particularly surprising behavior revealed by LEBDA is that tracers in the Lofoten Vortex with the same initial conditions can have radically different experiences. Their trajectories can vary, and they have different lifetimes and numbers of rotations around the vortex before they escape. Moreover, when they do escape, it happens in groups, with water leaving the eddy in bursts rather than a continuous flow.

“This clearly demonstrates that eddy boundaries are not static or uniform barriers, but dynamically evolving structures governed by chaotic advection,” said Belonenko.

LEBDA is a flexible framework that can be applied beyond Lofoten to study other climatically relevant dynamics. The authors envision its use in automated, long-term monitoring of eddies and their effects on their local biochemistry and ecosystem.

Source: “Lagrangian modeling of marker transfer at the Lofoten vortex periphery using R-contours and altimetry data,” by E. V. Novoselova, M. V. Budyansky, M. Yu. Uleysky, T. V. Belonenko, A. A. Udalov, and A. A. Didov, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0292208 .