Abstract
The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude. This provides valuable information to undertake Lagrangian dispersion studies by means of models and/or of observational data. Moreover, our results show that the relative dispersion rates measured at submesoscale are significantly higher than for large-scale dynamics. Auxiliary analysis of high resolution GPS-tracked drifter hourly data as well as of the drogued/undrogued status of the buoys is provided in support of our conclusions. A possible application of our study, concerning reverse drifter motion and error growth analysis, is proposed relatively to the case of the missing Malaysia Airlines MH370 aircraft.
Highlights
North Pacific sub-tropical gyre North Atlantic sub-tropical gyre Equatorial Indian current system Equatorial Pacific current system Equatorial Atlantic current system Southern Indian sub-tropical gyre Southern Pacific sub-tropical gyre Southern Atlantic sub-tropical gyre
Since the presence of the drogue in the Surface Velocity Program (SVP) type of buoy is supposed to guarantee the correct Lagrangian tracking of the ocean surface currents, and since a buoy may lose the drogue during its motion, we investigated the sensitivity of the Finite-Scale Lyapunov Exponent (FSLE) computation to all possible combinations occurring for a drifter pair: both drifters with drogue attached, one drifter drogued and the other one undrogued, both drifters without drogue attached, or any of the previous cases
The sample size is essentially determined by the filter imposed to the maximum initial separation allowed, i.e. only drifter pairs with initial separation ≤Δ= 10 km are taken into account, which is a good compromise between maximizing the number of pairs and keeping the FSLE analysis within reasonable physical constraints
Summary
The main goal of this work is to present a study of the relative dispersion properties in the ocean upper layer, through the analysis of surface drifter data from NOAA Global Drifter Program, described in detail in the Data section.
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