the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
15 Jan 2021
15 Jan 2021
Enhanced internal tidal mixing in the Philippine Sea mesoscale environment
- 1CAS Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- 2Pilot National Laboratory for Marine Science and Technology, Qingdao, China
- 3Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- 4College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
- 5Polar Research Institute of China, Shanghai, China
- 6China-Asean College of Marine Science, Xiamen University Malaysia, Sepang, Malaysia
- 1CAS Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- 2Pilot National Laboratory for Marine Science and Technology, Qingdao, China
- 3Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- 4College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
- 5Polar Research Institute of China, Shanghai, China
- 6China-Asean College of Marine Science, Xiamen University Malaysia, Sepang, Malaysia
Abstract. Turbulent mixing in the ocean interior is mainly contributed by internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well-known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from ARGO float data using a strain-based finescale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating its spatial pattern. One interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing for the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the mid-latitudes, wind-mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal-mixing was more predominant in the lower-latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing was greatly elevated in regions of energetic mesoscale processes. The anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than did cyclonic ones.
Jia You et al.
Status: closed
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RC1: 'Comment on npg-2021-1', Anonymous Referee #1, 03 Feb 2021
The paper deals with an interesting and important problem, namely the mechanism(s) resposible for oceanic mixing in a topographically-complex region. The data have been processed satisfactorily and they show some interesting features, though the interpretation of these features is not straightforward. My principal difficulty with the paper lies in the analysis of the data and the validity of the conclusions drawn from such an analysis. The heart of the analysis is the correlation of observed features of the diapycnal diffusivity patterns with the main causes of mixing identified by the authors. Many of the correlations claimed by the authors seem to be based either on visual inspection of the data plots or analysis based upon ratios of the energy fluxes associated with each of the driving agencies (e.g Fig 4) . I did not find these analyses convincing and I would have appreciated some more quantitative and rigorous data correlation procedures carried out to justify the conclusions. Figs 6, 7 and 8 are very difficult to interpret. Overall, I found the data analysis to be rather superficial and, in consequence, the conclusions unjustified by the evidence of the data analysis.
There are a few typographic and/or grammatical errors but, in general, the standard of english is satisfactory. The main error is to use "rates" instead of "ratios" in the correlation analyses (line 250 and elsewhere). The use of "slopes" instead of "ratios" (e.g line 319 and elsewhere) is misleading also (if I have understood the text correctly). In equation (3) I assume that "acrcosh" should be "arccosh"?
- AC1: 'Reply on RC1', Zhenhua Xu, 24 Feb 2021
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RC2: 'Comment on npg-2021-1', Anonymous Referee #2, 07 Feb 2021
The present manuscript describes spatial pattern and seasonal variability of the diapycnal diffusivities in the Philippine Sea. It was shown that seasonal variability was strong in winter and weak in summer at mid-latitudes, with the seasonal fluctuations more obvious in the upper ocean. The diapycnal diffusivitie that is spatially inhomogeneous were estimated from ARGO float data with the fine scale parameterization. The present manuscript is good scientific quality and well written. The obtained results are interesting however revision is needed:
1. More convincing comparison and analysis is needed for diapycnal diffusivities scatters fig 6-7.
2. As far as in fig 3 (diapycnal diffusivities) and fig 5 (Vertical structures of geometric averaged diapycnal diffusivities) Philippine Sea was divided for two zones (a) 10°N -25°N and (b) 25°N-35°N, but on figures 6-7 Philippine Sea was divided into three zones 10°N -15°N, 15°N-25°Nand 25°N-35°N it is difficult to compare the results for zone (10-25) and make a conclusions about that results on fig 6-7 is consistent with the results of Fig.3 and Fig.4.
3. In line 182 H is described as is the mixed-layer depth and was set to a constant 25m, however in Eq (8) H(Ð) – near-inertial energy flux.
4. Typo in Figure 3 Seasonal cycles in diapycnal diffusivities (colorful line) and near-inertial energy flux from wind (green) extents to 250-500 m, 500-1000 m and 1000-1500 m in (a) 10°N -25°N and (b) 10°N-25°N (should be 25°N -35°N ).
- AC2: 'Reply on RC2', Zhenhua Xu, 24 Feb 2021
Status: closed
-
RC1: 'Comment on npg-2021-1', Anonymous Referee #1, 03 Feb 2021
The paper deals with an interesting and important problem, namely the mechanism(s) resposible for oceanic mixing in a topographically-complex region. The data have been processed satisfactorily and they show some interesting features, though the interpretation of these features is not straightforward. My principal difficulty with the paper lies in the analysis of the data and the validity of the conclusions drawn from such an analysis. The heart of the analysis is the correlation of observed features of the diapycnal diffusivity patterns with the main causes of mixing identified by the authors. Many of the correlations claimed by the authors seem to be based either on visual inspection of the data plots or analysis based upon ratios of the energy fluxes associated with each of the driving agencies (e.g Fig 4) . I did not find these analyses convincing and I would have appreciated some more quantitative and rigorous data correlation procedures carried out to justify the conclusions. Figs 6, 7 and 8 are very difficult to interpret. Overall, I found the data analysis to be rather superficial and, in consequence, the conclusions unjustified by the evidence of the data analysis.
There are a few typographic and/or grammatical errors but, in general, the standard of english is satisfactory. The main error is to use "rates" instead of "ratios" in the correlation analyses (line 250 and elsewhere). The use of "slopes" instead of "ratios" (e.g line 319 and elsewhere) is misleading also (if I have understood the text correctly). In equation (3) I assume that "acrcosh" should be "arccosh"?
- AC1: 'Reply on RC1', Zhenhua Xu, 24 Feb 2021
-
RC2: 'Comment on npg-2021-1', Anonymous Referee #2, 07 Feb 2021
The present manuscript describes spatial pattern and seasonal variability of the diapycnal diffusivities in the Philippine Sea. It was shown that seasonal variability was strong in winter and weak in summer at mid-latitudes, with the seasonal fluctuations more obvious in the upper ocean. The diapycnal diffusivitie that is spatially inhomogeneous were estimated from ARGO float data with the fine scale parameterization. The present manuscript is good scientific quality and well written. The obtained results are interesting however revision is needed:
1. More convincing comparison and analysis is needed for diapycnal diffusivities scatters fig 6-7.
2. As far as in fig 3 (diapycnal diffusivities) and fig 5 (Vertical structures of geometric averaged diapycnal diffusivities) Philippine Sea was divided for two zones (a) 10°N -25°N and (b) 25°N-35°N, but on figures 6-7 Philippine Sea was divided into three zones 10°N -15°N, 15°N-25°Nand 25°N-35°N it is difficult to compare the results for zone (10-25) and make a conclusions about that results on fig 6-7 is consistent with the results of Fig.3 and Fig.4.
3. In line 182 H is described as is the mixed-layer depth and was set to a constant 25m, however in Eq (8) H(Ð) – near-inertial energy flux.
4. Typo in Figure 3 Seasonal cycles in diapycnal diffusivities (colorful line) and near-inertial energy flux from wind (green) extents to 250-500 m, 500-1000 m and 1000-1500 m in (a) 10°N -25°N and (b) 10°N-25°N (should be 25°N -35°N ).
- AC2: 'Reply on RC2', Zhenhua Xu, 24 Feb 2021
Jia You et al.
Jia You et al.
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