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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.


Related in: MedlinePlus

Current and hydrographic observations.Time series of (a) 40–440 m and (b) 1000–1450 m horizontal velocity magnitude observed by mooring A from 5 Mar 2012 to 18 June 2012. Time series of (c) temperature (lines) and temperature anomaly (colors) and (d) temperature at around 1463 m from 5 Mar 2012 to 18 June 2012. (e–g) Similar as (a–c) but observed by mooring B at different depths. (h) Salinity time series at 1160–1435 m observed by mooring B from 5 Mar 2012 to 18 June 2012. White lines in (a) represent 0.15 m/s contour. Red lines in (b,f) represent 75% lines of good data obtained from ADCPs outputs. The data in the layers shallower than red lines have more than 75% good quality with values. Note that red line in (b) can only be observed around April 14, 2012 at about 1450 m. In this figure, different colorbars are used. Figures are plotted using MATLAB.
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f2: Current and hydrographic observations.Time series of (a) 40–440 m and (b) 1000–1450 m horizontal velocity magnitude observed by mooring A from 5 Mar 2012 to 18 June 2012. Time series of (c) temperature (lines) and temperature anomaly (colors) and (d) temperature at around 1463 m from 5 Mar 2012 to 18 June 2012. (e–g) Similar as (a–c) but observed by mooring B at different depths. (h) Salinity time series at 1160–1435 m observed by mooring B from 5 Mar 2012 to 18 June 2012. White lines in (a) represent 0.15 m/s contour. Red lines in (b,f) represent 75% lines of good data obtained from ADCPs outputs. The data in the layers shallower than red lines have more than 75% good quality with values. Note that red line in (b) can only be observed around April 14, 2012 at about 1450 m. In this figure, different colorbars are used. Figures are plotted using MATLAB.

Mentions: Moorings A and B are deployed adjacent to Xisha Trough at approximately water depth of 1700 m and 1550 m, respectively (Fig. 1; see Method for detail). The velocity amplitudes in the deeper layer (larger than 1000 m) observed at moorings A and B are less than 0.02 m/s for most of the time (Fig. 2b,f). An interesting event is that two maximum velocities with the amplitude of 0.18 m/s occur between 4 April and 8 May 2012 at mooring A. Larger velocity amplitude in the deeper layer can also be observed in Mooring B (Fig. 2f) in May 2012. Observed by sediment trap at 1500 m at mooring B, total particle flux increases abruptly from 179 mg/m2/d in May to 398 mg/m2/d in July 2012, which presents obvious different fluctuation with that during the same period in 2010 and 201116. It has been reported that strong surface eddies in the SCS can extend vertically to thousands of meters, and thus induce larger velocity in deep layer17 and transport sediments6. What contributes to the larger velocity amplitude and sediments increase in deep layer shown by the mooring arrays?


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)

Current and hydrographic observations.Time series of (a) 40–440 m and (b) 1000–1450 m horizontal velocity magnitude observed by mooring A from 5 Mar 2012 to 18 June 2012. Time series of (c) temperature (lines) and temperature anomaly (colors) and (d) temperature at around 1463 m from 5 Mar 2012 to 18 June 2012. (e–g) Similar as (a–c) but observed by mooring B at different depths. (h) Salinity time series at 1160–1435 m observed by mooring B from 5 Mar 2012 to 18 June 2012. White lines in (a) represent 0.15 m/s contour. Red lines in (b,f) represent 75% lines of good data obtained from ADCPs outputs. The data in the layers shallower than red lines have more than 75% good quality with values. Note that red line in (b) can only be observed around April 14, 2012 at about 1450 m. In this figure, different colorbars are used. Figures are plotted using MATLAB.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Current and hydrographic observations.Time series of (a) 40–440 m and (b) 1000–1450 m horizontal velocity magnitude observed by mooring A from 5 Mar 2012 to 18 June 2012. Time series of (c) temperature (lines) and temperature anomaly (colors) and (d) temperature at around 1463 m from 5 Mar 2012 to 18 June 2012. (e–g) Similar as (a–c) but observed by mooring B at different depths. (h) Salinity time series at 1160–1435 m observed by mooring B from 5 Mar 2012 to 18 June 2012. White lines in (a) represent 0.15 m/s contour. Red lines in (b,f) represent 75% lines of good data obtained from ADCPs outputs. The data in the layers shallower than red lines have more than 75% good quality with values. Note that red line in (b) can only be observed around April 14, 2012 at about 1450 m. In this figure, different colorbars are used. Figures are plotted using MATLAB.
Mentions: Moorings A and B are deployed adjacent to Xisha Trough at approximately water depth of 1700 m and 1550 m, respectively (Fig. 1; see Method for detail). The velocity amplitudes in the deeper layer (larger than 1000 m) observed at moorings A and B are less than 0.02 m/s for most of the time (Fig. 2b,f). An interesting event is that two maximum velocities with the amplitude of 0.18 m/s occur between 4 April and 8 May 2012 at mooring A. Larger velocity amplitude in the deeper layer can also be observed in Mooring B (Fig. 2f) in May 2012. Observed by sediment trap at 1500 m at mooring B, total particle flux increases abruptly from 179 mg/m2/d in May to 398 mg/m2/d in July 2012, which presents obvious different fluctuation with that during the same period in 2010 and 201116. It has been reported that strong surface eddies in the SCS can extend vertically to thousands of meters, and thus induce larger velocity in deep layer17 and transport sediments6. What contributes to the larger velocity amplitude and sediments increase in deep layer shown by the mooring arrays?

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.


Related in: MedlinePlus