Ocean heat content in the Iberian–Biscay–Ireland regional seas

de Pascual-Collar, Álvaro; Aznar, Roland; Levier, Bruno; García-Sotillo, Marcos

doi:https://doi.org/10.5194/sp-1-osr7-9-2023

Articles | Volume 1-osr7

https://doi.org/10.5194/sp-1-osr7-9-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Report:

7th edition of the Copernicus Ocean State Report (OSR7)

https://doi.org/10.5194/sp-1-osr7-9-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 1-osr7

27 Sep 2023

| OSR7 | Chapter 2.7

| 27 Sep 2023 | OSR7 | Chapter 2.7

Ocean heat content in the Iberian–Biscay–Ireland regional seas

Álvaro de Pascual-Collar, Roland Aznar, Bruno Levier, and Marcos García-Sotillo

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Final revised paper (published on 27 Sep 2023)
Supplement to the final revised paper
Preprint (discussion started on 23 Sep 2022)

Interactive discussion

Status: closed

RC1:
'Comment on sp-2022-3', Anonymous Referee #1, 13 Oct 2022

Please see attached PDF report. Overall it is an interesting report, specially the sections links ocean heat content with water masses.

I believe the OHC averaged over the entire region (Figure 1) were swaped between 0-150 and 0-700m. If not, then the values and some of the results and conclusions of the text need to be revised.

Citation: https://doi.org/10.5194/sp-2022-3-RC1
- AC2:
  'Reply on RC1', Álvaro de Pascual Collar, 29 Dec 2022
  Dear editor,
  The authors would like to thank the review and the constructive comments. We consider most of the observations proposed by the reviewer contribute to improving the quality of the paper. Therefore, we are open to write a new version of the manuscript including all of them.
  Since the new version of the manuscript will include the recommendations provided by both reviewers (RC1, and RC2) the authors propose the following mayor changes:
  Figure 1 will be modified showing trends in the whole time record (period 1993-2020) and in the period 2005-2019. The text will be consequently adapted to discuss these trends.
  
  We will modify section 4 showing the regional trends not only for the period 2005-2019 but also for the whole period 1993-2020. The different results computed in these two periods will be discussed in the text.
  
  In section 5 we propose to analyse the OHC profiles in two different periods: 1993-2010 and 2010-2018. These two periods are proposed to represent two different behaviours of NAO index (negative trend in the period 1993-2010 and positive trend in the period 2010-2018). We consider this analysis can reinforce our conclusions highlighting the concordance of results with the hypothesis developed on Leadbetter et al. (2007), Bozec et al. (2011), and Pascual-Collar et al. (2019).
  
  Please see the attached document where we discuss point-by-point the reviewer’s comments and elaborate on the proposed changes.
  
  Citation: https://doi.org/10.5194/sp-2022-3-AC2
RC2:
'Comment on sp-2022-3', Cesar Gonzalez-Pola, 12 Nov 2022

Dear Editor.

I have read the manuscript entitled Ocean Heat Content in the Iberian-Biscay-Ireland regional seas by Pascual-Collar et.al

The manuscript makes use of different Copernicus products that provide, or allows computing, Ocean Heat Content in the IBI region. The work describes the spatio-temporal characteristics and also in terms of depth level integration of OHC series obtained in relationship to water masses in the region.

While I do not appreciate inconsistencies in the analysis, I feel that at this stage the manuscript does not present enough new and relevant research to merit a paper on its own. The analysis consists of computing linear trends from a number of available Copernicus products, and the discussion on the outcomes appears to me too descriptive and sketchy. I think that further work is needed in order to improve the manuscript. Some proposals are indicated below.

My first concern regards the purpose and value of using (and averaging) 5 different products. I understand that this work is not focused on product intercomparison and detailed documentation of each product is linked on table 1. I expect all products should yield similar outcomes since the bulk of baseline data comes from available ship-based hydrography and Argo floats, however further details on differences between products and especially on the causes of these differences will add value. If all products are very similar there is no point in averaging all five available, otherwise it would be interesting a discussion on which product may suit better. I am in particular confused about differences between the two reanalysis IBI-REA and GLO-REA since both have same resolution and coverage.

My second concern is that the discussion on OHC changes in relationship to water masses is too brief. Changes are interpreted in terms of boundaries advance/retreat, while no definition on boundaries is provided nor are insights on circulations changes that may cause such boundaries shits. I elaborate further on the specific comments.

--

Specific Comments

l.8 (abstract). The statement that OHC has increased not only globally but at regional scales is almost self-evident; OHC cannot increase globally if it does not also increase in [many/most] regions.

l.10 “observed derived products” sounds weird to me.

l.15. There is no contradiction between (1) having significant warming and (2) having OHC variability dominated by thermohaline variability of subsurface waters. Indeed, it is neither ‘thermohaline variability’ dominating ‘OHC variability’ nor the other way around, both are equivalent. I guess authors are trying to convey that interannual variability due to advective patterns dominate the thermohaline variability/OHC. This should be made clearer across the ms. This is said again in the short summary.

l.100. It is indicated that the level 150m is chosen to ‘analyse the OCH varibility in the mixing layer’, however mixed layer depth varies strongly across the IBI domain from several hundredths of meters west of Ireland to tenths in the south (e.g. http://mixedlayer.ucsd.edu/). If authors wish to analyze OHC variability/trends in the mixing layer they should not use a fixed 150 m reference depth.

l.128. ss. the authors highlight the increase of OHC for the whole period 1993-2020 but in the next section it is decided to compute trends for the period 2005-2019 since the global Argo array become dense enough, and this period shows a cooling.

l.184. the cooling trends in Fig.3 are computed for the period 2005-2019, so the statement that this is consistent with changes in thermocline thickness described in 2007 by Leadbetter et.al. (right at the start of the series or even before) deserves further explanation. Is it that the process described by Leadbetter initiated cooling trends in the IBI region? Is it suggested that this mechanism continued operating the following decade?. The authors should notice the large scale North Atlantic freshening/cooling well documented for the 2010s (e.g. https://doi.org/10.1038/s41467-020-14474-y https://doi.org/10.17895/ices.pub.7537)

l.189. the discussion on the displacement of the MOW boundaries in the Horseshoe basin requires further explanation. I do not see clear relationship between displacements of the 'MOW boundaries' westward and warming/salt increase in the region (besides, boundaries are not defined). As long as source waters properties do not vary, a westward shift of the boundary should only cause warming west of the original boundary placement. The warming/salt-increase in this sub-basin makes me feel that the waters are slowed/retained. If so, possible reasons should be discussed.

l.194. Again about the limits of the MOW, I disagree that the warming in the 43N box (on the northwards pathway of the MOW vein) indicates a westward movement of the MOW tongue.

l.202 Section 6. Data availability. The products used have been already described; I do not think this 2-line section is necessary.

l.216 OHC changes expressed in W/m3 (power density), should read W/m2?. Also in Table 2.

Figure 3. The procedure to obtain the averaged dots (markers) in the TS diagrams is not explained.

Citation: https://doi.org/10.5194/sp-2022-3-RC2
- AC1:
  'Reply on RC2', Álvaro de Pascual Collar, 29 Dec 2022
  Dear editor,
  The authors would like to thank the reviewer for their valuable comments. After a carefully read of the comments, we can partly understand them, and we think they can be considered to improve the manuscript. Therefore, we propose to include the following mayor changes in the contribution that mainly affect sections 4 and 5:
  We will include in the introduction a clear description of the main objective of this article (the evaluation of the Ocean Monitoring Indicator in the IBI region).
  
  We will consider the proposals indicated by the reviewer to give a better discussion on the outcomes.
  
  We will deeply modify sections four (Analysis of regional trends) and five (Analysis of OHC trends across different water masses) to analyse the consistency of results and the relevance of interannual variability on OHC trends.
  
  We will work on the conclusions highlighting the scientific contributions of this work.
  
  Please see the attached document where we discuss point-by-point the reviewer’s comments and elaborate on the proposed changes.
  
  Citation: https://doi.org/10.5194/sp-2022-3-AC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Publish subject to revisions (further review by editor and referees) (29 Dec 2022) by Marta Marcos

AR by Álvaro de Pascual Collar on behalf of the Authors (09 Mar 2023) Author's response Manuscript

EF by Polina Shvedko (13 Mar 2023) Author's tracked changes

ED: Referee Nomination & Report Request started (13 Mar 2023) by Marta Marcos

RR by Anonymous Referee #1 (28 Mar 2023)

Suggestions for revision or reasons for rejection

L54 – ‘proposed covering’ – something missing
L58 – remove ‘constitute’
L68 – remove comma after dynamics
L70 – in ‘the’ IBI region
L135: ‘differentiation’ implies a mathematical derivative function. I think you actually wanted to say ‘difference’?
L136 – the different products were interpolated to which grid?
L132-145: not necessary to say lat/lon maps, just maps is enough; The same for lat/lon ensemble, ‘spatial ensemble’ is enough.
L139: “Then the vertical integrations and spatial average ‘were’ (not was) obtained”
L140-141 says the same thing as L136-137.
L149 – should it be ‘Section 5’ here? (Section 6 should be the data availability section, which is missing from the revised manuscript)
L150: Which NAO index was used? The one provided by NOAA[1] and by NCAR [2], for example, are slightly different. And can you add a plot of the NAO index to the manuscript or to supplementary? I am not sure if I would say that it was moderately positive from 1993-2010, but actually mainly negative, with a minimum in 2010, and then a mainly positive behavior. The description in L211-212 seems more accurate.
L156: you use ‘time series’ here, with space, and in other instances ‘timeseries’. Please be consistent (I would suggest time series, with space).
L167: And are the trends from 0-2000m significantly? A trend of 0.4 with an uncertainty of 0.39 doesn’t seem very robust… I would still dare to say that the intermediate layers (150-700m) dominate the OHC variability, since the difference from 0-700 and 0-2000m is almost negligible.
L190: typo ‘shake’
L192: Suggest to add a reference depth to the mixing layer, since this can vary a lot depending on the region.
L223: at the end of the sentence, I think it should be ‘35’ and not ‘24’, referring to the region centered at 35˚N.
L241: ‘boundary transports of MOW and NAO’. I guess you meant to say something else than ‘NAO’ here? The boundary of MOW should either be with other water masses or with another region.
L246: ‘occupies’ should then refer to a depth; a water mass occupy a certain depth, or has a certain thickness.
L255: remove comma after both.
L259: Suggest to replace ‘despite’ for ‘although’.
L251: Section 6 is missing.

[1]: https://www.ncei.noaa.gov/access/monitoring/nao/
[2]: https://climatedataguide.ucar.edu/climate-data/hurrell-north-atlantic-oscillation-nao-index-station-based

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ED: Publish subject to technical corrections (31 Mar 2023) by Marta Marcos

ED: Publish subject to minor revisions (review by editor) (31 Mar 2023) by Marilaure Grégoire (Chief editor)

AR by Álvaro de Pascual Collar on behalf of the Authors (12 Apr 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (17 Apr 2023) by Marta Marcos

ED: Publish as is (23 Apr 2023) by Marilaure Grégoire (Chief editor)

AR by Álvaro de Pascual Collar on behalf of the Authors (03 May 2023) Author's response Manuscript

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Short summary

The article comprises the analysis of the ocean heat content in the northeastern Atlantic Iberian–Biscay–Ireland (IBI) region. The variability of ocean heat content is studied, and results are linked with the variability of the main water masses found in the region. Results show how the coupled interannual variability of water masses accounts for an important part of the total ocean heat content variability in the region.