Global observations of large oceanic eddies

Abstract

[1] Ten years of sea-surface height (SSH) fields constructed from the merged TOPEX/Poseidon (T/P) and ERS-1/2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean. The higher resolution of the merged dataset reveals that more than 50% of the variability over much of the World Ocean is accounted for by eddies with amplitudes of 5 -25 cm and diameters of 100-200 km. These eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic Rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies, respectively. The vast majority of the eddies are found to be nonlinear.

Pathways of mesoscale variability in the South China Sea

“…In the eastern and central SCS, mesoscale signals mainly show the westward propagation velocities, which are widely observed in the world oceans and attributed to the influence of baroclinic Rossby waves (Morrow et al, 2004;Chelton et al, 2007). Thus the eddy energy generated west of the Luzon Island will transfer westward, resulting in weak local MV.…”

“…To focus on the mesoscale and reduce the incidence of spurious MCC vectors, the maximum possible velocity is set at 26 km/day (30 cm/s), which is generally larger than the propagation speeds of eddies (Chelton et al, 2007). Meanwhile, the phase speeds of baroclinic Rossby waves are mostly lower than 30 cm/s as well (Gan and Cai, 2001).…”

“…Mesoscale fluctuations on temporal-spatial scales between 20-150 days and 50-500 km dominate the oceanic variability (Wyrtki et al, 1976;Richman et al, 1977) and are largely accounted for by eddies (Chelton et al, 2007). In the SCS, besides seasonal variability, the circulation also displays energetic mesoscale variability (MV).…”

Eddy energy sources and sinks in the South China Sea

“…Kinetic energy of eddies is greater than that of mean flows by more than 1 order of magnitude [Wyrtki et al, 1976;Richardson, 1983;Ferrari and Wunsch, 2009]. Once generated, eddies propagate westward with their energy eventually dissipated, or transferred vertically into high-mode motions near the western boundary [Chelton et al, 2007[Chelton et al, , 2011Zhai et al, 2010]. The eddy energy budget in estimation of the energy generation and dispersion is subjected to several uncertainties, and specifically it is found to be sensitive to parameterizations of thickness diffusion coefficient [Gent et al, 1995;Marshall and Adcroft, 2010].…”

A Gaussian-surface-based approach to identifying oceanic multi-eddy structures from satellite altimeter datasets

“…Automatic eddy identification algorithms are essential for helping scientists efficiently gain insights from large volumes of observation datasets, and are becoming a very important research topic in oceanography in recent years. Existing algorithms can be approximately divided into three groups: 1) physical parameter based [12][13][14], 2) flow geometry based [15][16][17], and 3) sea level anomaly (SLA) based [18][19][20]. Although various novel algorithms have been developed, few address the problem of identifying the multi-eddy structures (Fig.…”