Differences between 1999 and 2010 across the Falkland Plateau: fronts and water masses

Pérez-Hernández, M. Dolores; Hernández-Guerra, Alonso; Comas-Rodríguez, Isis; Benítez-Barrios, Verónica M.; Fraile-Nuez, Eugenio; Pelegrí, Josep L.; Naveira Garabato, Alberto C.

doi:https://doi.org/10.5194/os-13-577-2017

Articles | Volume 13, issue 4

https://doi.org/10.5194/os-13-577-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/os-13-577-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 4

Research article

|

07 Jul 2017

Research article |

| 07 Jul 2017

Differences between 1999 and 2010 across the Falkland Plateau: fronts and water masses

M. Dolores Pérez-Hernández, Alonso Hernández-Guerra, Isis Comas-Rodríguez, Verónica M. Benítez-Barrios, Eugenio Fraile-Nuez, Josep L. Pelegrí, and Alberto C. Naveira Garabato

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Final revised paper (published on 07 Jul 2017)
Preprint (discussion started on 13 Dec 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Additional analysis is needed about the water properties and transport between 1999 and 2010', Anonymous Referee #1, 05 Feb 2017
- AC1: 'Response to Reviewer 1', M. Dolores Pérez-Hernández, 04 Mar 2017
RC2: 'Review of the manuscript “Properties and mass transport differences across the Falkland Plateau between 1999 and 2010” by M. Dolores Pérez-Hernández et al. (MS No. os-2016-89).', Anonymous Referee #2, 27 Mar 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Maria Dolores Pérez-Hernández on behalf of the Authors (17 Apr 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Apr 2017) by Mario Hoppema

RR by Anonymous Referee #1 (18 May 2017)

RR by Anonymous Referee #2 (02 Jun 2017)

Suggestions for revision or reasons for rejection

The authors have taken on board many of the comments in my original review, but not all of them. Perhaps my explanations were not clear enough. I have endeavoured to give clear explanations in my comments below. As with the earlier version, with revisions, I believe that this manuscript would be a useful addition to the literature.

In my original review, I noted that:
“The title “Properties and mass transport differences across the Falkland Plateau between 1999 and 2010” does not express what the importance of the paper is. The values calculated are “volume transport” (units of metres cubed per second), not “mass transport” (units of kilograms per second). “Properties” is too vague – which properties? A title that summarises the key message or focus of the paper is needed.”
The authors’ response was:
“We agree that the paper can use some clarification in stating which kind of transport units are used throughout the text. In line 32 we have described the relation between the units of mass and volume transport and specified that transport will be expressed in Sv. In addition, later in line 86 we have clarified now that the study uses mass transport. We have also changed the title to include the words “fronts” and “water masses”.”
The new title is “Differences between 1999 and 2010 across the Falkland Plateau: Fronts and water masses”, and this is an improvement. The authors say that they have “specified that the transport will be expressed in Sv”, yet they persist in referring to the transport throughout as “mass transport”, rather than “volume transport”. “Volume transport” is the normal phrase used in oceanography for the property measured in Sv, and I do not understand why the authors insist on calling this “mass transport”.

In my original review, I noted for what are now lines 66-72:
“This paragraph basically says that the paper is organized with data and methods first, then results, then discussions and conclusions. Almost all scientific papers are organised that way, so this paragraph could be deleted. A more useful thing to have in its place would be a sentence that starts with “In this paper,. . .”, followed by the most important thing(s) that the paper shows/examines.”
The authors’ response was:
“We would like to keep this paragraph. Although it does not provide with important information it presents the outline of the manuscript, so the reader can decide what parts are more relevant for his/her purpose. On the other hand, the previous paragraph (lines 59-65) already states the important subjects that the paper examines.”
I don’t know any readers who look for a paragraph at the end of the introduction to work out which parts are relevant to them. Most people with whom I have discussed “how do you read/review a paper?” say that they read the abstract first, then go through all the figures, then read the conclusion to see if it matches what they think the figures show, then look at the section headings in sequence, then read the text. I think the authors could strengthen the sentence at lines 62-65 to say what was achieved (currently it is stated as an objective), and finish the introduction there.

Line 81:
In my original review, I noted that:
“An accuracy of 0.001 C would mean that the SBE911+ CTD on the ship was new from the factory or had been recently calibrated (or post-cruise factory calibrated), because the specifications of the SBE911+ CTD say this is the initial accuracy, with a drift of “0.0002 C per month” (http://www.seabird.com/sbe911plus-ctd, under specifications tab). This may not be important for the level of accuracy required for the measurements presented in this manuscript, but more details should be given.”
The authors’ response was:
“The CTD was sent to SeaBird for calibration before the cruise.” However, the authors’ have not added this information to the manuscript. I believe it is an important detail, as not all CTDs are sent for pre- and post-cruise calibrations.
At line 81, after the words “…and temperature sensors.”, the authors should add the sentence “The CTD was sent to SeaBird for calibration before the cruise.”

Lines 84-85:
The authors have misunderstood my suggestion, and they have not made any changes to the manuscript in this respect. In my original review, I stated:
“…the reference for PSS should be cited at the end of this sentence.”
The authors have responded with:
“As the reviewer says we have used the Practical Salinity Scale and this is specified in lines 84-85 of the manuscript to avoid confusion.”, but they have not made any changes to the manuscript.
By “reference”, I meant that the authors should cite the paper/report that the PSS derives from:
Unesco. 1981a. The Practical Salinity Scale 1978 and the International Equation of State of Seawater 1980. Techn. Pap. mar. sci, 36: 25 pp.

Section 3.5:
In my original review, I suggested rewording parts of section 3.5 to say: “The relative net transport is 9.2 Sv less during 2010 compared to during the ALBATROSS cruise as an outcome of a weaker SAF in 2010.” I also suggested “How 14.7 Sv less volume transport of the SAF leads to 9.2 Sv reduction in net transport would also be worth explaining , that is why volume transport changes are not directly additive.” The authors state in their response:
“We have changed the first two paragraphs of section 3.5 following this comment from the reviewer.” The authors have changed the start of the second paragraph to read as follows:
“The relative net transport during the MOC-Austral cruise is 9.2 Sv weaker than in the ALBATROSS cruise as an outcome of a more intense SAF. SASW, AAIW/AASW and UCDW present lower values in 2010 than in 1999, being the surface and intermediate stratums the ones with the highest decadal transport differences (Figure 7 and table 1).”
The version of the first sentence that I suggested, “…weaker SAF in 2010”, and the authors’ new version, “more intense SAF” seem to be contradictory. Figure 3 and Figure 7 show that the SAF was weaker in 2010, but the way the authors have put “more intense SAF” with no qualifiers makes the reader infer that the SAF was more intense in 2010 (MOC-Austral cruise). I suggest that the words “more intense SAF” be followed by “in 1999” for clarity.

Figure 1:
The authors have mostly followed my suggestions for changes, except that they have omitted the word “black” for the 2010 station numbers. I suggest this caption is modified to read “…MOC-Austral (2010, black station numbers)…” I agree with the other reviewer that it would be better to have consistent colouring of stations between Figure 1(a) and Figure 1(b) (and later figures). Changing the red station points/numbers in Figure 1(a) to grey would be the easiest way to do that.

Figure 10:
This figure was added in response to a suggestion from the other reviewer. The figure shows accumulated relative geostrophic mass transport from AVISO 1993-2016 for all months of February and April, as well as ALBATROSS (April 1999) and MOC-Austral (February 2010) data. The AVISO February and April data look like a smoothed version of the ALBATROSS data, and are very different from the MOC-Austral data. In the discussion section, more discussion on this would be interesting. Also, what was Figure 10 in the earlier version of the manuscript (maps of wind stress) is now Figure 11, but that figure is still referred to as Figure 10(a,b,c), which needs to be corrected.

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ED: Publish subject to minor revisions (Editor review) (02 Jun 2017) by Mario Hoppema

AR by Maria Dolores Pérez-Hernández on behalf of the Authors (06 Jun 2017) Author's response Manuscript

ED: Publish subject to technical corrections (07 Jun 2017) by Mario Hoppema

AR by Maria Dolores Pérez-Hernández on behalf of the Authors (07 Jun 2017) Author's response Manuscript

Short summary

The decadal differences between the ALBATROSS (April 1999) and MOC2-Austral (February 2010) hydrographic cruises are analyzed. Changes in the intermediate water masses beneath seem to be very sensitive to the wind conditions existing in their formation area. The Subantarctic Front is wider and weaker in 2010 than in 1999, while the Polar Front remains in the same position and strengthens.