Drivers for Atlantic-origin waters abutting Greenland

Gillard, Laura C.; Hu, Xianmin; Myers, Paul G.; Ribergaard, Mads Hvid; Lee, Craig M.

doi:https://doi.org/10.5194/tc-14-2729-2020

Articles | Volume 14, issue 8

https://doi.org/10.5194/tc-14-2729-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-14-2729-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 8

Research article

|

27 Aug 2020

Research article |

| 27 Aug 2020

Drivers for Atlantic-origin waters abutting Greenland

Laura C. Gillard, Xianmin Hu, Paul G. Myers, Mads Hvid Ribergaard, and Craig M. Lee

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Final revised paper (published on 27 Aug 2020)
Preprint (discussion started on 02 May 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of Gillard et al. Drivers for Atlantic-origin waters abutting Greenland.', Anonymous Referee #1, 28 May 2019
- AC1: 'Authors Response to Reviewer 1', Laura Gillard, 13 Aug 2019
RC2: 'Review', Anonymous Referee #2, 15 Jun 2019
- AC2: 'Authors Response to Reviewer 2', Laura Gillard, 13 Aug 2019

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (30 Aug 2019) by David M Holland

AR by Laura Gillard on behalf of the Authors (02 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Jan 2020) by Dirk Notz

RR by Anonymous Referee #1 (11 Feb 2020)

RR by Anonymous Referee #2 (26 Feb 2020)

Suggestions for revision or reasons for rejection

This is my second review of this paper. I appreciate that the authors have now included some model validation against observations, that is very helpful and it makes the results more relevant.
Also it was nice to see the separation out heat flux seasonality into the volume flux vs temperature seasonality.
However, there are a few things that have not improved, at least in my view.
There are several instances where the discussion of explanation of model results is not supported by the analysis and that needs to be corrected.
Further, much of the discussion of results are rather qualitative than quantitative and in my view that should be changed.
Finally, I have some concerns about the heat flux calculations which are stated below. If these concerns are relevant a significant portion of the manuscript would have to be revised.

Major:

Eddy heat flux calculation:

I am wondering what is used for T in Equation 2.
I am worried the authors are using temperature in Celsius to calculate this quantity, at least Figure 9 suggests that. At all panels the sign of the heat flux is the sign of the product of the volume flux and temperature signs, rather than the sign of the volume flux (e.g. Fig 9p).
The temperature needs to be referenced in some meaningful way, for example to absolute zero by using Kelvin, or to the freezing point (so using Thermal driving in stead of Temperature in the calculation) but as that varies with depth and properties it might be more complicated to calculate.
Further, the section across which the heat flux seasonality is calculated should be marked on Fig. 8. For example in Fig. 9g the volume flux is negative all the time so the authors are showing here the seasonality of the outflow more so then the seasonality of the inflow. Either way though these two are mixed up in the way the analysis is done. I think a better way to do this would be to integrate only the inflow to the trough as that is the focus of this paper.

Seasonality discussion:

While heat flux is integrated over the full depth for the purposes of showing seasonality, the closing discussion 3.1.7 explains this seasonality in terms of Irminger water seasonality. My problem here is that the integrated number contains both Irminger and polar water (and potentially other water masses), but the discussion only talks about Irminger water as if that was the only water included in the analysis. Either the analysis needs to be corrected to separate out the different water masses, or the discussion needs to be adjusted to what is actually shown in the paper. I think the former would be better.

Mean flow vs fluctuation analysis:

The authors should pick a metric by which they will evaluate the importance of fluctuations. The discussion should then be formulated in a more rigorous way, e.g. this fraction of heat flux is mediated by fluctuations and this by mean flow. A follow up discussion can then compare the importance of fluctuations between the different section.
There is a persistent intermingling of results and discussion and it sounds all very subjective an hand wavy.
Also the comparison between low res vs high res and mean vs fluctuation should be separated as these are two different topics. It doesn't appear that the fluctuation component is higher for the high res simulations, is it that the resolution change was insufficient to resolve smaller scale processes, or could a different timescale averaging choice substantially change the results? There is no clear conclusion about wether high res is better or worse than low res and so I wonder what is the point of the plots in Fig. 10 (red vs black line).
There were lots of typos in this section, also the word order throughout the manuscript is making it difficult to read smoothly. Please have coauthors proofread.

Double melt experiment:

There is no analysis of the results. I agree it is interesting to see comparison of a section with melt and double melt and observe they are different. However, without understanding how this modeling results was produced (mechanisms responsible for this) I don't see much value to the publishing of this finding.

Fluctuations:

Wrong units, this further extends to the abstract where the quantities computed in this section are reported.

Minor:

For the model validation - could you provide a TS diagram with both model and observations?

Could you include a table listing all the different water masses referred to in the manuscript and include the TS definitions of those?

Additional comments are in the attached pdf.

Referee Report: PDF

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ED: Reconsider after major revisions (further review by editor and referees) (03 Mar 2020) by Dirk Notz

AR by Laura Gillard on behalf of the Authors (28 Apr 2020) Author's response

ED: Referee Nomination & Report Request started (14 May 2020) by Dirk Notz

RR by Anonymous Referee #2 (25 May 2020)

ED: Publish subject to minor revisions (review by editor) (15 Jun 2020) by Dirk Notz

AR by Laura Gillard on behalf of the Authors (25 Jun 2020) Author's response Manuscript

ED: Publish as is (06 Jul 2020) by Dirk Notz

Short summary

Greenland's glaciers in contact with the ocean drain the majority of the ice sheet (GrIS). Deep troughs along the shelf branch into fjords, connecting glaciers with ocean waters. The heat from the ocean entering deep troughs may then accelerate the mass loss. Onshore heat transport through troughs was investigated with an ocean model. Processes that drive the delivery of ocean heat respond differently by region to increasing GrIS meltwater, mean circulation, and filtering out of storms.