Mesoscale Eddies in the Northwestern Pacific Ocean: Three‐Dimensional Eddy Structures and Heat/Salt Transports

Dong, Di; Brandt, Peter; Chang, Ping; Schütte, Florian; Yang, Xiaofeng; Yan, Jinhui; Zeng, Jing

doi:10.1002/2017jc013303

Cited by 73 publications

(68 citation statements)

References 47 publications

(90 reference statements)

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“…Here, we compare our results with the previous multiple regional studies, including Atlantic, Pacific, and Agulhas Ring (Table ). Comparisons in different regions show that the derived penetrating depth D from the aspect ratio well agree with results inferred using other technical methods, for example, eddies in the Kuroshio extension extending down to approximately 800 m as inferred from inspecting the water mass properties anomaly (Dong et al, ; Sun et al, ). Our results show that the penetrating depth D of eddies in this region is approximately 800 m, which agrees well with the previous authors' conclusions.…”

Section: Resultssupporting

confidence: 63%

Aspect Ratio of Eddies Inferred From Argo Floats and Satellite Altimeter Data in the Ocean

Liu

Liao

et al. 2020

JGR Oceans

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Mesoscale eddies dominate the majority of oceanic kinetic energy. The size of eddies is one of the basic properties; however, little is known about it because of lack of observations. Especially, their global vertical extent has still not been well investigated. Here, a ratio relationship of height to length scale for an eddy is derived based on dynamical constraints. Global satellite altimetry data combined with Argo float observations are used to calculate the aspect ratios of mesoscale eddies in the global ocean, and then their vertical scale is inferred. Approximately 25% of the total identified eddies with lifetimes ≥16 weeks from January 2002 to December 2017 trapped at least an Argo float near the eddy center. The result shows that the size of eddies has an obvious latitudinal dependence. Eddies at middle-low latitudes tend to be "large and shallow" with small aspect ratios, and eddies at high latitudes tend to be "small and deep-reaching" with large aspect ratios. Such results are coarsely considered as a competition between rotation and stratification. Eddy aspect ratios in middle-high-latitude regions show enhanced variance compared to those in low-latitude regions. More than half of eddies have a vertical extent smaller than 400 m. The majority of eddies extend over the mixed layer depth and are instead situated in the pycnocline. Some eddies at the middle-high latitudes penetrate through the entire pycnocline and reach deep ocean; as such, these eddies may play an important role in linking the deep-sea circulations and the surface circulations.Key Points:• The size (length and depth) of eddies has a distinct latitudinal dependence • More than half of eddies have a vertical extent smaller than 400 m • More than 70% of eddies penetrate through the entire pycnocline and reach deep ocean

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Section: Resultssupporting

confidence: 63%

Aspect Ratio of Eddies Inferred From Argo Floats and Satellite Altimeter Data in the Ocean

Liu

Liao

et al. 2020

JGR Oceans

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“…Figure 2 shows the area-mean EKE in the Kuroshio extension region at different depths. The EKE is surface intensified with an e-folding decaying depth of about 400 m, consistent with the observed eddy structures in this region (Dong et al 2017). The reduction of EKE in CTRL to those in noU tot and noU e is most evident at the sea surface and diminishes gradually as the depth increases.…”

Section: Resultssupporting

confidence: 86%

Impacts of ocean current–atmosphere interactions on mesoscale eddy energetics in the Kuroshio extension region

et al. 2020

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The surface ocean current's imprint on the wind stress (known as the current feedback) has a significant influence on the wind power input to the ocean. In this study, we investigate the effect of the current feedback on mesoscale eddy energetics in the Kuroshio extension region using a high-resolution (9 km) coupled regional climate model. We perform three sets of simulations: one calculates the wind stress without the surface current, one includes only the mesoscale eddy's current and another includes the entire current in the computation. In this way, the mesoscale eddy's current feedback can be isolated and its contribution to the entire current feedback can be assessed. The simulation results show that the mesoscale eddy's current feedback results in negative wind power input to mesoscale eddies and reduces the surface eddy kinetic energy (EKE) by ~ 20% in the Kuroshio extension region. This negative wind power is compensated primarily by the enhanced conversion from mean flow kinetic energy (MKE) and eddy potential energy (EPE) to EKE and secondarily by the reduced pressure flux divergence and horizontal dissipation. Compared to the mesoscale eddy's current feedback, the entire current feedback has a similar impact on EKE and the wind power on mesoscale eddies, while it affects the EKE budget differently. It weakens the MKE to EKE conversion partly due to the reduced kinetic energy input to background flows by wind. Correspondingly, the negative wind power on mesoscale eddies is primarily compensated by the enhanced EPE to EKE conversion.

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“…The flow field was observed by the shipboard ADCP instruments and the maximum was close to 0.90 m s −1 at 48 m depth. Comparing with the composite results of Argo profiles in the Kuroshio Extension region [12,60], the observed 3D anatomy shows more details and new results, such as vertical monopole and dipole structures of temperature and salinity anomaly, horizontal dipole and monopole structures of temperature and salinity in the mixed layer and the equivalent barotropic flow structure.…”

Section: Discussionmentioning

confidence: 69%

Anatomy of a Cyclonic Eddy in the Kuroshio Extension Based on High-Resolution Observations

Zhang

Chen

2019

Atmosphere

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Mesoscale eddies are common in the ocean and their surface characteristics have been well revealed based on altimetric observations. Comparatively, the knowledge of the three-dimensional (3D) structure of mesoscale eddies is scarce, especially in the open ocean. In the present study, high-resolution field observations of a cyclonic eddy in the Kuroshio Extension have been carried out and the anatomy of the observed eddy is conducted. The temperature anomaly exhibits a vertical monopole cone structure with a maximum of −7.3 • C located in the main thermocline. The salinity anomaly shows a vertical dipole structure with a fresh anomaly in the main thermocline and a saline anomaly in the North Pacific Intermediate Water (NPIW). The cyclonic flow displays an equivalent barotropic structure. The mixed layer is deep in the center of the eddy and thin in the periphery. The seasonal thermocline is intensified and the permanent thermocline is upward domed by 350 m. The subtropical mode water (STMW) straddled between the seasonal and permanent thermoclines weakens and dissipates in the eddy center. The salinity of NPIW distributed along the isopycnals shows no significant difference inside and outside the eddy. The geostrophic relation is approximately set up in the eddy. The nonlinearity-defined as the ratio between the rotational speed to the translational speed-is 12.5 and decreases with depth. The eddy-wind interaction is examined by high resolution satellite observations. The results show that the cold eddy induces wind stress aloft with positive divergence and negative curl. The wind induced upwelling process is responsible for the formation of the horizontal monopole pattern of salinity, while the horizontal transport results in the horizontal dipole structure of temperature in the mixed layer. species composition (EDDIES) in the Sargasso Sea off Bermuda [5], meso-and submesoscale processes in an intense front (AlborEx) [6] and the northwestern Pacific eddies, internal waves and mixing Experiment (NPEIM) [7], and so forth. Nowadays, main observation methods for field experiment include Argo floats, moored instrumentation, underwater gliders and shipboard survey.Argo profiling floats, which are designed to measure underwater ocean temperature and salinity (T/S) [8], are one of the effective methods to obtain 3D mesoscale eddy structures [9][10][11][12][13]. However, due to the drift features, the detailed structure of a specific eddy is difficult to acquire unless a large number of Argo floats are deployed inside the targeted mesoscale eddy. Reference [14] deployed 17 rapid-sampling Argo floats to study the anticyclonic eddies effects on mode water subduction in the south of the Kuroshio Extension to the east of Japan. In situ mooring observations can usually collect temperature, salinity and current data from the bottom to the surface at a fixed-point where the eddy moves through. Reference [15] designed and conducted a multi-month field campaign to capture the full-depth 3D structure of a pair of anticyclonic and c...

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Mesoscale Eddies in the Northwestern Pacific Ocean: Three‐Dimensional Eddy Structures and Heat/Salt Transports

Cited by 73 publications

References 47 publications

Aspect Ratio of Eddies Inferred From Argo Floats and Satellite Altimeter Data in the Ocean

Aspect Ratio of Eddies Inferred From Argo Floats and Satellite Altimeter Data in the Ocean

Impacts of ocean current–atmosphere interactions on mesoscale eddy energetics in the Kuroshio extension region

Anatomy of a Cyclonic Eddy in the Kuroshio Extension Based on High-Resolution Observations

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