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Observed deep energetic eddies by seamount wake.

Chen G, Wang D, Dong C, Zu T, Xue H, Shu Y, Chu X, Qi Y, Chen H - Sci Rep (2015)

Bottom Line: It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s).The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy.Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.

ABSTRACT
Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

No MeSH data available.


Observed current vectors.Time series of velocities observed by mooring A at different depths from 29 Feb 2012 to 19 May 2012. Figure is plotted using MATLAB.
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f3: Observed current vectors.Time series of velocities observed by mooring A at different depths from 29 Feb 2012 to 19 May 2012. Figure is plotted using MATLAB.

Mentions: Structure of larger velocity amplitude in the deeper layer is obviously asynchronous from that of the upper water column. For example, at mooring A, a velocity core with a local maximum of 0.18 m/s at 1100 m occurs on May 5 (Fig. 2b), while the maximum velocity amplitude is only 0.13 m/s at 400–440 m and no obvious velocity core is observed at 200–440 m at that time (Fig. 2a). Larger velocity amplitude with the value of 0.15 m/s (the white line in Fig. 2a) is observed in the upper 460 m layer before April 19. However, the isoline of 0.15 m/s gradually rises to 150 m on May 19. The discrepancy of the upper and deep layers between March 20 and May 9, 2012 at mooring A can be better viewed in velocity vectors (Fig. 3). Because of the effect of the surface cyclonic eddy, the counterclockwise rotation is presented in the upper 400 m layer. Different from the situation in the upper layer, very weak velocities are observed in the layer below 1000 m before April 9. After April 9, the water deeper than 1000 m spins clockwise. These results suggest that the local maximum of the current speed at 1100 m shown in Fig. 2b is not an extension of the surface cyclonic eddy. The highest temperature at 1460 m between March and June appears on April 25, 2012 with the value of 3.05 °C (Fig. 2d), 0.16 degree warmer than the mean temperature at the depth. Note that April 25 is also the middle time of the two maximum velocity amplitudes observed by mooring A in the deeper layer (Fig. 2b).


Observed deep energetic eddies by seamount wake.

Chen G, Wang D, Dong C, Zu T, Xue H, Shu Y, Chu X, Qi Y, Chen H - Sci Rep (2015)

Observed current vectors.Time series of velocities observed by mooring A at different depths from 29 Feb 2012 to 19 May 2012. Figure is plotted using MATLAB.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663540&req=5

f3: Observed current vectors.Time series of velocities observed by mooring A at different depths from 29 Feb 2012 to 19 May 2012. Figure is plotted using MATLAB.
Mentions: Structure of larger velocity amplitude in the deeper layer is obviously asynchronous from that of the upper water column. For example, at mooring A, a velocity core with a local maximum of 0.18 m/s at 1100 m occurs on May 5 (Fig. 2b), while the maximum velocity amplitude is only 0.13 m/s at 400–440 m and no obvious velocity core is observed at 200–440 m at that time (Fig. 2a). Larger velocity amplitude with the value of 0.15 m/s (the white line in Fig. 2a) is observed in the upper 460 m layer before April 19. However, the isoline of 0.15 m/s gradually rises to 150 m on May 19. The discrepancy of the upper and deep layers between March 20 and May 9, 2012 at mooring A can be better viewed in velocity vectors (Fig. 3). Because of the effect of the surface cyclonic eddy, the counterclockwise rotation is presented in the upper 400 m layer. Different from the situation in the upper layer, very weak velocities are observed in the layer below 1000 m before April 9. After April 9, the water deeper than 1000 m spins clockwise. These results suggest that the local maximum of the current speed at 1100 m shown in Fig. 2b is not an extension of the surface cyclonic eddy. The highest temperature at 1460 m between March and June appears on April 25, 2012 with the value of 3.05 °C (Fig. 2d), 0.16 degree warmer than the mean temperature at the depth. Note that April 25 is also the middle time of the two maximum velocity amplitudes observed by mooring A in the deeper layer (Fig. 2b).

Bottom Line: It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s).The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy.Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.

ABSTRACT
Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

No MeSH data available.