On the statistical properties of sea-ice lead fraction and heat fluxes in the Arctic

Ólason, Einar; Rampal, Pierre; Dansereau, Véronique

doi:https://doi.org/10.5194/tc-15-1053-2021

Articles | Volume 15, issue 2

https://doi.org/10.5194/tc-15-1053-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-15-1053-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 2

Research article

|

26 Feb 2021

Research article |

| 26 Feb 2021

On the statistical properties of sea-ice lead fraction and heat fluxes in the Arctic

Einar Ólason, Pierre Rampal, and Véronique Dansereau

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Final revised paper (published on 26 Feb 2021)
Preprint (discussion started on 28 Jan 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review: ‘On the statistical properties of sea ice lead fraction and heat fluxes in the Arctic’', Anonymous Referee #1, 25 Feb 2020
- AC1: 'Reply to revier #1', Einar Örn Ólason, 16 Jun 2020
RC2: 'Review of “On the statistical properties of sea ice lead fraction and heat fluxes in the Arctic”', Nils Hutter, 10 Mar 2020
- AC2: 'Reply to revier #2', Einar Örn Ólason, 16 Jun 2020

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (02 Jul 2020) by Petra Heil

AR by Einar Örn Ólason on behalf of the Authors (03 Jul 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Jul 2020) by Petra Heil

RR by Anonymous Referee #1 (13 Aug 2020)

Suggestions for revision or reasons for rejection

Please note that line numbers refer to the copy of the manuscript with differences marked up.

The reviewers have mostly addressed my comments from the first review. The revised text includes a few typos and is clumsy in places.

Main points to be addressed prior to publication:

Can you be sure that the lack of small leads in the observations explains all of the difference between model and observations up to 40% lead fraction? It is also possible that the model is biased at lead fractions below 40%. I don’t think the statements at L230 that
• ‘agreement between model and reality is probably better than a first-order interpretation of figure 3 would suggest’; and
• ‘Perhaps a fairer comparison between the model simulation and observations would therefore consider only lead fractions larger than 40%’
are justified based on what has been presented in the manuscript.

In a similar vein, there is no justification presented for claiming that there is ‘noise’ in the observations (Fig. 3 caption).

The authors conclude that, ‘The model reproduces the PDF and scaling of observed lead fraction in the Central Arctic very well.’ (L383) This seems too strong, and I think it should be rephrased to something like ‘shows agreement with observations for lead fractions over 40%’

The following points aren’t necessary to address, but the authors may wish to consider:

Regarding my previous comment on the thin ice threshold-
It seems somehow artificial to me to compute the thin ice threshold based by tuning the model output to observations, when a model-observation comparison is being performed. In the end, it doesn’t really matter because the value is more or less the same as the value of 10 cm noted in the citation for the observational product, but I don’t really understand why the authors didn’t just use the 10 cm value.

The authors have added some broader motivation in the Introduction, but I think the manuscript would still benefit from some discussion of broader implications in the Conclusions/Summary (which is rather abrupt).

Line-by-line comments (should be addressed)

L21: remove ‘in the centre of the Arctic Basin’ after ‘Leads’

L40: When referring to ‘larger’ and ‘smaller’ leads, what is the approximate length scale?

L45: ‘model results are lacking in several aspects.’ Such as?

L58: ‘he’ should be ‘the’

L62: ‘the statistical properties of leads in large-scale sea-ice models have not yet been shown to be robustly reproduced’ I think this means to say that the models have not yet been shown to reproduce observations

L64: Add comma after deforms

L110: Typo, ‘comparable’

L115: Typo, ‘results’

L124: You might add that the cohesion parameter appears in the Mohr-Coulomb criterion

L126: Are the Bouillon & Rampal 2015a and 2015b references listed the right way round? I think they might be mixed up

L169: Mentions snapshots – but text above states that only daily means are used. Remove ‘snapshots’?

L178: Perhaps say, ‘as a a function of spatial scale’

L179: Remove ‘the’, before ‘log-log space’

L186: Suggest removing the first part of the sentence, and simply say ‘B(q) is the structure function, which ’…

L190: This paragraph is a bit clumsy, consider rewording

Fig. 1 caption: The last sentence should be in the main text rather than in the caption. How do you know that the observational product displays ‘noise’ rather than real leads? This needs to be justified.

L208: suggest rewording to ‘Figure 2 shows the PDF of observed and simulated lead fraction in the Central Arctic on a log-log scale. On this scale, both the observed and the simulated PDF’…

Fig. 3 caption: should include brief description of the error bars

L271: I don’t think differences of 20% and 30% should be described as ‘nearly the same’

L292: ‘This fractal character is inherited from the multifractal character of the ice deformation rates, as discussed below.’ This sentence is unnecessary and can be removed.

L369: replace ‘should otherwise’ with ‘would otherwise’

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ED: Publish subject to minor revisions (review by editor) (03 Oct 2020) by Petra Heil

AR by Einar Örn Ólason on behalf of the Authors (19 Nov 2020) Author's response Manuscript

ED: Publish subject to technical corrections (29 Dec 2020) by Petra Heil

I thank the author for their rewrite of this manuscript which resulted in a much approved version. Before final acceptance, pls provide an updated version with view of the technical issues identified below.

General:
* I abbreviate "manuscript" with "ms".
* Throughout the ms, pls correct "e.g." to "e.g.,".
* Ensure use of SI units throughout the ms, e.g., 136 "10 cm" -> "0.1m".
* With advise from the TC Editorial Team, pls apply correct reference style
for figure and table calls. I.e., 225 "(figure 4b)" does not look correct.

Specific comments:
67: Change "give us" to "provide".
68: Corret "solids as sea ice" to "solids such as sea ice".
70: Change "which in turn triggers more deformation nearby" to
"which in turn may give rise to further ice deformation nearby".
72: Capitalize "Earth".
73: Correct "smaller quakes more distributed in the vicinity" to "smaller
smaller quakes more distributed in the vicinity"
73: Correct "smaller quakes more distributed in the vicinity" to "smaller
quakes occurring in the wider vicinity".
75: Change "using observations and the neXtSIM model" to "using both, observations
and the neXtSIM model".
76: Correct "we present briefly" to "we briefly present".
77: Correct "In section 3" to "In Section 3".
80: Change "— which is done in section 4" to "(Section 4)".
81: Correct "section 5" to "Section 5".
82: Correct "depends" to "depend".
82: Correct "section 6" to "Section 6".
84: Correct "Arctic basin." to "Arctic Basin."
91: Correct "thermodynamics model" to "thermodynamic model".
94: Remove "a category of".
122: Suggest to replace "to degrade significantly" with "to diverge significantly".
136: Pls use SI units.
145: Clarify the exact mathematical procedure when "combine all the daily means",
i.e., explain "combine".
182: Pls use SI units.
194: Rewrite "the PDF for the observations flattens out" to improve English.
Caption Fig. 5 right: I cannot see a line for "linear ... fit".
Caption Fig. 5: Correct "topp" to "top".
267: Correct "12 km" to "12.5 km".
327: Correct "in at" in "smaller effect in at the time scales".
376: Correct "this data" to "these data".
376: Correct "The source code to neXtSIM" to "The neXtSIM source code".
Acknowledgement: Suggest to change "an anonymous reviewer" to "an anonymous 2nd reviewer".
--------

Note: References not checked, nor referencing cross-checked. --> Editorial service: Pls
carry these tasks. Thank you.

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AR by Einar Örn Ólason on behalf of the Authors (06 Jan 2021) Author's response Manuscript

Short summary

We analyse the fractal properties observed in the pattern of the long, narrow openings that form in Arctic sea ice known as leads. We use statistical tools to explore the fractal properties of the lead fraction observed in satellite data and show that our sea-ice model neXtSIM displays the same behaviour. Building on this result we then show that the pattern of heat loss from ocean to atmosphere in the model displays similar fractal properties, stemming from the fractal properties of the leads.