The Seasonal Variation of the Anomalously High Salinity at Subsurface Salinity Maximum in Northern South China Sea from Argo Data

Round 1

Reviewer 1 Report

With the extensive Argo data set over decade in the north South China Sea area, the authors present seasonal changes of vertical structure of salinity profile. The manuscript is well-written, presenting clear figures and sound reason for their discussion of the variation of the anomalously high salinity at subsurface salinity maximum. I recommend publishing this manuscript after following minor revisions if needed for better clarity.

In the sub section 4.2 of Discussion, it is not clear which period was targeted for the estimation of the mean wind stress curl with the NCEP reanalysis data. I recommend more explanation for the wind field information for the analysis of the wind stress curl also in the sub section.

Another minor item is on the Line 193. What does it mean with “in the revised manuscript”?

Author Response

Please see the attachment. Thank you very much!

Author Response File: Author Response.pdf

Reviewer 2 Report

This study investigates the variability of sub-surface maximum salinity in the northern South China Sea using the ARGO profiles. The authors clearly show the seasonal variability of the sub-surface maximum and the anomalously high salinity and contributions of major water masses in the region. The authors also demonstrate the main physical drivers contributing to salinity change in the sub-surface maximum. Tthe subject itself is of great interest for the physical oceanography/climate research community of Southeast Asia Seas. The manuscript is well introduced, well organised and well written. Their analysis is well founded and findings are quite robust. However, I think that their analysis and therefore their discussion could be pushed further whilst there are some other points which need to be addressed prior to publication (see comments below).

 

Major comments:

The authors could construct monthly/seasonal timeseries over the whole ARGO period used in the study (e.g. 2006-2019) of area-averaged salinity of the sub-surface maximum for the whole region and various sub-regions (e.g. as defined in Figure 9) to clearly demonstrate seasonal variability but also inter-annual variations. They could then correlate these timeseries with area-averaged timeseries of main contributing drivers of the variability as these investigated in this study (e.g. Ekman pumping, eddies, etc).

Another important component that I think is missing in the analysis is the large-scale seasonal/interannual natural variability that can affect salinity of the sub-surface salinity maximum. Especially ENSO has a significant impact on salinity in this region since rainfall over the Southeast Asian seas has strong positive correlations to a la Nina-like SST anomaly pattern (e.g. Caesar et al. 2011).

 

 

Minor comments:

• Title: The authors mainly deal with the seasonal variation of the anomalously high salinity in subsurface maximum, so they should include the word “seasonal” in their title except if they follow my point made above about extending this study to investigate inter-annual variability.

 

• Abstract, line 21: … extracted from decades of Argo data …

 Please be precise: state the number of years

 

• Introduction Line 40: …is a water mass cross region for coastal water and ocean water, and thus is an important region …

Please rephrase/explain further

 

• In the abstract the authors highlight the importance of salinity sub-surface maximum variations for the hydrological cycle but then nothing mentioned at all in the introduction or in the discussion/conclusion sections. The authors could briefly discuss in the introduction how the sub-surface salinity maximum increase is linked with an amplification of the global hydrological cycle (see studies of Helm et al. 2010; Skliris et al. 2014, in the reference list below).

 

• Line 193: From Figure 7a in the revised manuscript …

revised manuscript??  Please rephrase

 

• Line 201: “… the statistical result of salinity of the salinity maximum data shows an obvious skewed distribution”.

Please re-phrase

• Line 204: “ Some data were less than the mode, but most were greater than the mode

Use of English is not correct. Please rephrase

• Line 220: north Pacific water …

Do you mean “NPTW”?

 

• Line 243: “… because the NPTW that intrude into NSCS hardly reach at this place before mixing in the NSCS”.

Any references to support this?

 

• Figure 9 needs larger fonts

 

• Figure 11: Winter/Summer panels are not described in the caption (Fonts also too small for Winter/Summer titles on the figure panels)

 

• Line 304: “mesoscale eddies have a conservative property because of their high nonlinearity”

 

Explain – provide reference

 

 

References

Caesar J, et al. (2011). Changes in temperature and precipitation extremes over the Indo-Pacific region from 1971 to 2005. International Journal of Climatology 31: 791–801.

Helm KP, Bindoff NL, Church JA (2010) Changes in the global hydrological-cycle inferred from ocean salinity. Geophys Res Lett 37:L18701. doi:10.1029/2010GL044222

Skliris N., Marsh R, Josey SA, Good SA, Liu C, Allan RP (2014). Salinity changes in the World Ocean since 1950 in relation to changing surface freshwater fluxes. Clim Dyn 43: 709-736.

  

 

Author Response

Please see the attachment. Thank you very much!

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors responded well to my queries/concerns and revised the manuscript accordingly. Therefore I suggest to accept the revised paper