Study of subsurface eddy properties in northwestern Pacific Ocean based on an eddy-resolving OGCM

Abstract

A method based on the Okubo-Weiss parameter was used to detect subsurface eddies (SSEs) with an eddy-resolving ocean general circulation model. Statistical analyses showed that SSEs are ubiquitous in the northwestern Pacific Ocean. Three regions were found to have high probability of SSE, which are as follows: the latitudinal band between 9°N and 17°N, the Kuroshio extension region, and the area east of the Ryukyu Islands. Although surface eddies (SEs) were found distributed widely within the zonal band of the Subtropical Counter Current, few SSEs were found there. In contrast, few SEs were found to the east of The Philippines, whereas SSEs were abundant. The kinetic energy contained within SSE was found comparable in magnitude with that of SE. During 1993, about 2569 and 2099 SSEs (at a depth of about 400 m) were observed to be anticyclonic and cyclonic, respectively; thus, SSEs tended to be anticyclonic. The mean radius, lifespan, and propagation speed of SSE in this study were about 60 km, 50 days, and 6.6 cm/s, respectively. The propagation speed showed a wave-like decrease with increasing latitude. Some long-lived SSEs were found to persist for longer than 4 months and to move thousands of kilometers. About 89% of SSEs were nonlinear for at least half their lifespan, which implies that SSE can trap interior fluid during translation. Trajectories revealed that SSEs propagate nearly due west with only small meridional deflection. The findings of this study will contribute to the enrichment of our knowledge regarding SSE in the northwestern Pacific Ocean.

Four Types of Baroclinic Instability Waves in the Global Oceans and the Implications for the Vertical Structure of Mesoscale Eddies

“…Zhang et al (2015) and Li et al (2017), respectively. The red shaded areas in the western North Pacific denote the regions where the occurrence frequency of subsurface eddies is higher than 5% (Xu et al, 2019). discussion focuses on zonal propagation.)…”

“…Xu et al. (2019) found a high occurrence of subsurface eddies in the low latitudes (10°N–20°N) of the northwestern Pacific Ocean based on the outputs of an eddy‐resolving ocean general circulation model. In addition, many subsurface eddies have also been detected in the Mediterranean Sea (McDowell & Rossby, 1978; Richardson et al., 2000) and in the Indian Ocean (Shapiro & Meschanov, 1991; Yang et al., 2019).…”

“…These eddies are distributed widely but are concentrated in the KE region, in the northern Atlantic and along strong subsurface currents, that is, the California Undercurrent and the Peru-Chile Undercurrent. Xu et al (2019) found a high occurrence of subsurface eddies in the low latitudes (10°N-20°N) of the northwestern Pacific Ocean based on the outputs of an eddy-resolving ocean general circulation model. In addition, many subsurface eddies have also been detected in the Mediterranean Sea (McDowell & Rossby, 1978;Richardson et al, 2000) and in the Indian Ocean (Shapiro & Meschanov, 1991;Yang et al, 2019).…”

Evidence of eddy-related deep-ocean current variability in the northeast tropical Pacific Ocean induced by remote gap winds

“…Most of the previous studies of mesoscale eddies in the Pacific Ocean have focused on the surface processes, and little is known about the impact of mesoscale eddies in the deep ocean, specifically on their current characteristics (for the northwestern Pacific see, e.g., Lee et al, 2013, andXu et al, 2019; for the southwestern Pacific see, e.g., Qu and Lindstrom, 2001;Keppler et al, 2018; and for the southeastern Pacific see, e.g., Chaigneau and Pizarro, 2005;Chaigneau et al, 2008;Stramma et al, 2014;and Thomsen et al, 2015). The study of Stramma et al (2014), however, had a particular focus on investigating the role of mesoscale eddies in the ocean current characteristics.…”

Evidence of eddy-related deep ocean current variability in the North-East Tropical Pacific Ocean induced by remote gap winds

“…Most of the previous studies of mesoscale eddies in the Pacific Ocean are focused on the surface processes and little is known about the impact of mesoscale eddies in the deep ocean, specifically on their current characteristics (e.g., for the northwestern Pacific see Lee et al (2013); Xu et al (2019), for the southwestern Pacific see Qu and Lindstrom (2001); Keppler et al (2018); Liu et al (2012) and for the southeastern Pacific see Chaigneau and Pizarro (2005); Chaigneau et al (2008); Stramma et al 65 (2014); Thomsen et al (2015)). The study of Stramma et al (2014), however, had a particular focus on investigating the role of mesoscale eddies on the ocean current characteristics.…”