Lagrangian Statistics and Intermittency in Gulf of Mexico

Liru Lin,Wei Zhuang,Yongxiang Huang

doi:10.1038/s41598-017-17513-9

Abstract

Due to the nonlinear interaction between different flow patterns, for instance, ocean current, meso-scale eddies, waves, etc, the movement of ocean is extremely complex, where a multiscale statistics is then relevant. In this work, a high time-resolution velocity with a time step 15 minutes obtained by the Lagrangian drifter deployed in the Gulf of Mexico (GoM) from July 2012 to October 2012 is considered. The measured Lagrangian velocity correlation function shows a strong daily cycle due to the diurnal tidal cycle. The estimated Fourier power spectrum E(f) implies a dual-power-law behavior which is separated by the daily cycle. The corresponding scaling exponents are close to −1.75 and −2.75 respectively for the time scale larger (resp. 0.1 ≤ f ≤ 0.4 day−1) and smaller (resp. 2 ≤ f ≤ 8 day−1) than 1 day. A Hilbert-based approach is then applied to this data set to identify the possible multifractal property of the cascade process. The results show an intermittent dynamics for the time scale larger than 1 day, while a less intermittent dynamics for the time scale smaller than 1 day. It is speculated that the energy is partially injected via the diurnal tidal movement and then transferred to larger and small scales through a complex cascade process, which needs more studies in the near future.

Highlights

The movement of the ocean is extremely complex due to the nonlinear interaction between different flow patterns, where turbulence may play an important role[1]
Numerical studies indicates that the Loop Current (LC)-topography interactions and ring shedding are both in favor of the formation and development of cyclonic eddies, during which cyclones primarily gain energy from LC as a consequence of mean-to-eddy energy conversion[18,19,20]
The northeastern Gulf of Mexico (GoM) is characterized by complex bathymetry, with a right-angle submarine valley, named the DeSoto Canyon, between two wide shelves

Summary

OPEN Lagrangian Statistics and Intermittency in Gulf of Mexico

Due to the nonlinear interaction between different flow patterns, for instance, ocean current, mesoscale eddies, waves, etc, the movement of ocean is extremely complex, where a multiscale statistics is relevant. It is a semi-enclosed marginal sea located west of the Atlantic Ocean, connected with the Atlantic Ocean to the east via the Florida Straits and the Caribbean Sea to the south via the Yucatan Channel. The northeastern GoM is characterized by complex bathymetry, with a right-angle submarine valley, named the DeSoto Canyon, between two wide shelves (the West Florida Shelf and the Mississippi-Alabama Shelf) In this region, the local winds, eddy activities, topographic waves and Mississippi River input could jointly influence the interplay between the shelf and deep circulations, resulting in notable cross-shelf exchanges[21,22,23,24]. A Kolmogorov-like scaling in space for the second-order Eulerian structure-function is obtained from the same Lagrangian drifter experiment[28]

Results

Possible Cascade Dynamics

Methods

Additional Information