Subthermocline eddies observed by rapid‐sampling Argo floats in the subtropical northwestern Pacific Ocean in Spring 2014

Zhang, Zhiwei; Li, Peiliang; Xu, Lixiao; Li, Cheng; Zhao, Wei; Tian, Jiwei; Qu, Tangdong

doi:10.1002/2015gl064601

Cited by 47 publications

(77 citation statements)

References 43 publications

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“…This point will be discussed in the subsection 3.3. Note that the observed SAE in this study is much larger than those subsurface eddies and most surface eddies in this region detected by previous researchers [27,[31][32][33].…”

Section: Observationscontrasting

confidence: 36%

“…Three-dimensional structure of such subsurface eddy in this region has never been shown by previous researchers due to the lack of in situ observations [29][30][31][32][33]. However, Argo data provided us an invaluable tool to composite three-dimensional structure of the subsurface eddy.…”

Section: Three-dimensional Structurementioning

confidence: 97%

“…This SAE contains the north Pacific Central Mode Water (CMW) characterized as low potential vorticity (PV). Two subsurface eddies (one SAE and one SCE) with horizontal length scale of ~20 km were observed by rapid-sampling Argo floats by Zhang et al [33]. According to the previous studies, subsurface eddies play an important role on the subsurface circulation, the water mass properties, and vorticity redistribution in the northwestern Pacific, which should be paid further attention.…”

Section: Argo Datamentioning

confidence: 99%

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Observations of an Extra-Large Subsurface Anticyclonic Eddy in the Northwestern Pacific Subtropical Gyre

Nan¹,

Yu²,

Wei³

et al. 2017

J Marine Sci Res Dev

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An extra-large subsurface anticyclonic eddy (SAE) with horizontal scale of 470 km was detected in the northwestern Pacific subtropical gyre by in situ measurements in October 2014. The SAE exhibited a lens-shaped vertical structure with shoaling of the seasonal thermocline and deepening of the main thermocline. Consequently, the water in the eddy core was colder above 200 m and warmer below 200 m than the surrounding waters with maximum temperature anomalies of -1.2°C and 3.5°C located at ~100 m and ~450 m depths, respectively. The central water mass of the SAE was characterized as low potential vorticity water, i.e., the north Pacific Subtropical Mode Water (STMW). Swirl velocity of the SAE was directly observed by ship-mounted ADCP (Acoustic Doppler Current Profilers). The maximum azimuthal velocity reached 0.35 ms -1 near a 110 km radius at ~ 200 m depth, which was comparable with the maximum velocity of the northward Kuroshio east of Taiwan at the same depth. Threedimensional structure and evolutionary process of the SAE were also presented using Argo float profile data as well as the satellite altimeter data. The results indicated that the SAE was generated in the region of the STMW in February, then propagated westward over 1500 km at a mean speed of ~0.06 ms -1 and finally disappeared east of Taiwan in December, transporting ~0.5 Sv (Sv=10 6 m 3 s -1 ) STMW..

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Section: Observationscontrasting

confidence: 36%

Section: Three-dimensional Structurementioning

confidence: 97%

Section: Argo Datamentioning

confidence: 99%

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Observations of an Extra-Large Subsurface Anticyclonic Eddy in the Northwestern Pacific Subtropical Gyre

Nan¹,

Yu²,

Wei³

et al. 2017

J Marine Sci Res Dev

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“…Mesoscale eddies are ubiquitous features of the world oceans and play a fundamental role in transferring physical and biological properties across different spatial and temporal scales (Chaigneau et al, ; Chelton et al, ; Dufois et al, ; Qiu & Chen, ; Zhang et al, ). The paradigm of a mesoscale eddy, known as a surface‐intensified eddy, features the occurrence of maximum geostrophic velocities at the surface.…”

Section: Introductionmentioning

confidence: 99%

“…Other types of eddies in the ocean which have their cores in the subsurface layer, are known as subsurface eddies or subsurface vortices (Kostianoy & Belkin, ; Mcwilliams, ). These can further be classified as subthermocline eddies (STEs), with the core below the thermocline, and intrathermocline eddies (ITEs), with the core between the seasonal and permanent thermoclines (Barceló‐Llull et al, ; Li et al, ; Nauw et al, ; Pelland et al, ; Zhang et al, ). The focus of this particular study is on surface and subsurface eddies in the Southern Indian ocean without distinguishing between different subsurface eddy‐types.…”

Section: Introductionmentioning

confidence: 99%

SIDDIES Corridor: A Major East‐West Pathway of Long‐Lived Surface and Subsurface Eddies Crossing the Subtropical South Indian Ocean

et al. 2018

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South Indian Ocean eddies (SIDDIES), originating from a high evaporation region in the eastern Indian Ocean, are investigated by tracking individual eddies from satellite data and co‐located Argo floats. A subsurface‐eddy identification method, based on its steric dynamic height anomaly, is devised to assign Argo profiles to surface eddies (surfSIDDIES) or subsurface eddies (subSIDDIES). These westward‐propagating, long‐lived features (>3 months) prevail over a preferential latitudinal band, forming a permanent structure linking the eastern to the western Indian Ocean, that we call the 'SIDDIES Corridor’. Key features have been revealed in the mean thermohaline vertical structure of these eddies. Anticyclonic SIDDIES are characterized by positive subsurface salinity anomalies, with subSIDDIES not exhibiting negative surface anomalies, as opposed to surfSIDDIES. Cyclonic subSIDDIES also occur, but their related salinity anomalies are weaker. SubSIDDIES exhibit two cores of different temperature polarities in their surface and subsurface levels. Cyclonic subSIDDIES have their cores at around 150‐200 m depth along the 25.4‐25.8 kg m−3 potential density layer with anticyclonic subSIDDIES having their cores at 250‐300 m along the 26‐26.4 kg m−3 density layer. The SIDDIES corridor acts as a zonal pathway for both eddy‐types to advect water masses and biogeochemical properties across the basin. This study provides a new insight on heat/salt fluxes, showing that 58% (32%) of the total heat eddy‐flux is ascribed to cyclonic (anticyclonic) subSIDDIES, respectively, in the eastern South Indian Ocean. Anticyclonic subSIDDIES have also been found to be the sole high‐saline water eddy‐conveyor toward the western Indian Ocean.

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A statistical study on the subthermocline submesoscale eddies in the northwestern Pacific Ocean based on Argo data

et al. 2017

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In this study, statistical characteristics and spatiotemporal variability of the cold‐core subthermocline eddies (STEs) discovered by Zhang et al. (2015) in the northwestern Pacific are investigated with 14 years of Argo temperature/salinity (T/S) data between 2002 and 2015. By applying an objective identification procedure to Argo T/S profiles, a total of 337 lens‐like STEs that trap cold and fresh homogeneous water are obtained. The STEs' cores are primarily located between 26.5 and 26.9 σ0 (300–800 m) and their shapes share a uniform Gaussian structure in vertical. Vertical and horizontal scale of the STEs is generally between 100 and 200 m and 5 and 15 km, respectively, suggesting that they are in the category of submesoscale processes. According to their different densities and seasonalities, the STEs are classified into upper and lower types with density interface of 26.7 σ0. The number of upper‐type STEs is much larger in spring and summer than in autumn and winter while that of lower‐type ones show relatively uniform seasonal distributions. Spatially, the STEs are primarily distributed within the region between the Kuroshio Extension (KE) and subarctic front (SAF) in meridional and 140°E–155°E in zonal direction. Based on STEs' spatial distributions and vertical locations, we propose to name these STEs as KE intermediate‐layer eddies (Kiddies). Water property analysis suggests that the Kiddies most likely originated from the SAF region. For the upper‐type Kiddies, they are probably generated through subduction associated with mixed‐layer frontogenesis, which at least contribute to 0.25 Sv annual subduction rate for the layers 26.2–26.7 σ0.

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Subthermocline eddies observed by rapid‐sampling Argo floats in the subtropical northwestern Pacific Ocean in Spring 2014

Cited by 47 publications

References 43 publications

Observations of an Extra-Large Subsurface Anticyclonic Eddy in the Northwestern Pacific Subtropical Gyre

Observations of an Extra-Large Subsurface Anticyclonic Eddy in the Northwestern Pacific Subtropical Gyre

SIDDIES Corridor: A Major East‐West Pathway of Long‐Lived Surface and Subsurface Eddies Crossing the Subtropical South Indian Ocean

A statistical study on the subthermocline submesoscale eddies in the northwestern Pacific Ocean based on Argo data

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