Gyration effect estimated from global surface drifter data in the Pacific Ocean

Two quantities supposed to measure the average effect of eddy rotation (gyration effect) in the upper ocean are discussed. The quantities under consideration are the gyration vector introduced in the theory of rotationally anisotropic turbulence and the spin following from the Lagrangian stochastic turbulence models. It is shown that while the gyration vector expresses an average kinematic effect of eddy rotation in a mechanically straightforward way, then the average spin combines the gyration effect with some other effects masking its kinematic sense. The meridional distributions of the zonally averaged gyration vector and the average spin estimated from the global surface drifter data measured in the Pacific Ocean of the depth exceeding 2 km between 120°E and 90°W show qualitative similarities and quantitative differences of the distributions.