Arctic sea ice anomalies during the MOSAiC winter 2019/20

Dethloff, Klaus; Maslowski, Wieslaw; Hendricks, Stefan; Lee, Younjoo J.; Goessling, Helge F.; Krumpen, Thomas; Haas, Christian; Handorf, Dörthe; Ricker, Robert; Bessonov, Vladimir; Cassano, John J.; Kinney, Jaclyn Clement; Osinski, Robert; Rex, Markus; Rinke, Annette; Sokolova, Julia; Sommerfeld, Anja

doi:https://doi.org/10.5194/tc-16-981-2022

Articles | Volume 16, issue 3

https://doi.org/10.5194/tc-16-981-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-16-981-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 3

Research article

|

14 Mar 2022

Research article |

| 14 Mar 2022

Arctic sea ice anomalies during the MOSAiC winter 2019/20

Klaus Dethloff, Wieslaw Maslowski, Stefan Hendricks, Younjoo J. Lee, Helge F. Goessling, Thomas Krumpen, Christian Haas, Dörthe Handorf, Robert Ricker, Vladimir Bessonov, John J. Cassano, Jaclyn Clement Kinney, Robert Osinski, Markus Rex, Annette Rinke, Julia Sokolova, and Anja Sommerfeld

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Final revised paper (published on 14 Mar 2022)
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Preprint (discussion started on 16 Feb 2021)
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Interactive discussion

Status: closed

RC1:
'Comment on tc-2020-375', Anonymous Referee #1, 02 Mar 2021

“Arctic sea ice anomalies during the MOSAiC winter 2019/20” by Klaus Dethloff et al., submitted to The Cryosphere

(General comments) This is an interesting paper describing the sea ice condition related to the atmospheric circulation patterns as indicated by AO, just in time to the conclusion of the MOSAiC expedition. Basically, the manuscript is well written and readable; however, some figures (4, 7, and 16) are too small and difficult to understand. Also, coordination of figures was better to be the same. If you take the one in Figure 12 as a basis, then Figures 2, 3, 5, 10, and 11 top (even different from 11 bottom) should be in the same one. Explanation of Figure 6 is not enough, and I don’t understand any advantage showing these two graphs. Are the “Target diagram” and “Taylor diagram” common style for statistical science? Also, “normalized bias”, “normalized uRMSD”, “normalized standard deviation”, and “REF” are not explained. Table 1 seems sufficient for necessary information. Summary and Conclusion section does not display conclusion clearly.

(Specific comments) - Line 165-167: Short description of the way (concept) to derive sea ice thickness from satellite data is better to be made for CryoSat-2/SMOS data, since most references are only technical reports, not easy to refer. - Line 208: Title for 3.1 should be analogous/ comparable to that of 3.2, such as “Analysis of atmospheric and sea ice condition in ERA-5 and satellite data” or so. The present title does not reflect 3.1.1. - Line 216: There is no explanation for Figure 1(b). Why (b) is based on 1979-2000 ERA-5? - Line 219, Figure 2: Figure 2 is unbalanced and if so, please make some indication in the figure months and Δp or ΔT and so on. - Line 255-257: It is difficult to read “1.3 m” as the maximum from Figure 4 (already point out in the general coment). Even the color bars are different between Figure 3 and 4! - Line 265-267: It is difficult to follow these two sentences because we have no information on the satellite algorithm (as noted above). - Line 274: What is “domain-averaged bias”? - Line 277: “Anomalies” mean difference from the mean 2010-2019? (as indicated in the captions of Figure 7). - Line 285-286: “ship-based measurements” mean EM measurements written on Line 176, then it better to describe so. - Line 288-290: Is there any other bias of ship-based EM measurements, such as calibration error or so? - Line 297-301: We are not sure where you are talking about since southern part was mostly covered with clouds in Figure 9. The small red letters could not read in the infrared image (left). In the BS, we could not see the surface/ leads? - Line 313-329: This paragraph is not clear to be understood. Figure 10 is also difficult to read. Small black arrows indicate transpolar drift, then, what are large black thin arrows? - Line 333: What is “OSI-SAF low resolution sea ice motion data”? Some explanation is needed. - Figure 11: What are large black arrows similar to be in Figure 10. - Line 350: Bering Street ---→ Bering Strait? - Line 363 and 369: TVT and DVT, too much abbreviations. We can accept for place names or common parameters, but physical phenomena should be written down? - Line 401-403: Might be an important message; however, not clear from the Figure 15. Difference is seen rather in the central Arctic. - Line 416-419: These message should be compared with Figure S2.

Citation: https://doi.org/10.5194/tc-2020-375-RC1
- AC1: 'Reply on RC1', Klaus Dethloff, 27 Apr 2021
  
  The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2020-375/tc-2020-375-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/tc-2020-375-AC1
RC2:
'Comment on tc-2020-375', Anonymous Referee #2, 31 Mar 2021

Review on “Arctic sea ice anomalies during the MOSAiC winter 2019/20” by Dethloff et al.

The study presents the characteristics of Arctic atmospheric circulation anomalies in winter 2019/20 and their effects on sea ice advection, thermodynamic and dynamic processes, as well as the variation of sea ice thickness in some regions. Combined with the ice thickness data obtained from satellite radar altimeter and the output of fully coupled regional climate model, this study attempts to separate the influence of sea ice thermodynamics and dynamics on sea ice thickening, and analyze the mechanism of atmospheric circulation anomalies affecting the process of thermodynamics and dynamics. It is an interesting work for the study on the process of Arctic sea ice on a seasonal scale and the mechanism of rapid change in Arctic sea ice. It's worth publishing in the TC. However, at present, there is still rooms for further improvement both in content and expression, thus, I recommend that the manuscript to be considered for publication after major revision.

Here are the comments:

General comments:

1) This work attempts to establish a close relationship with the related work of MOSAiC campaign, so as to support the subsequent analysis of mosaic observation data. This is a good point, however, the relationship between the analysis content in this paper and the work of MOSAiC is not so close. You only use the data from MOSAiC are the drift track of ice station and the summarized results of ice thickness observed from the supply vessel. Only way is to reduce the color of MOSAiC through the paper, e.g., change the title and rewrite the introduction. The other way, you can highlight anomalies of some MOSAiC observed parameters compared to the climatology, for example, the drifting trajectory vs. the historic buoys also operated along the Transpolar Drift Stream (e.g., Lei R, Heil P, Wang J, Zhang Z, Li Q, Li N. 2016. Characterization of sea-ice kinematic in the Arctic outflow region using buoy data. Polar. Res. 35: 22658. doi:10.3402/polar.v35.22658.), and the basic meteorological parameters (air temperature, wind, relative humidity) along the MOSAiC trajectory in 2019/20 vs. that obtained from the climatology…

2) The Arctic dipole is the most important pattern for the atmospheric circulation to influence the sea ice motion of the Transpolar Drift Stream (e.g., Vihma T, Tisler P, Uotila P. 2012. Atmospheric forcing on the drift of Arctic sea ice in 1989-2009. 39: 10.1029/2011gl050118.; Lei R, Gui D, Hutchings J K, Wang J, Pang X. 2019. Backward and forward drift trajectories of sea ice in the northwestern Arctic Ocean in response to changing atmospheric circulation. 39: 4372-4391.), but not the AO. Therefore, to analyze the influence of atmospheric circulation on sea ice processes through the Transpolar Drift Stream, it is necessary to fully discuss the influence of Arctic dipole, associated with AO.

Specially comments:

1) Along-track ship-based ice thickness measurementsï¼it would be better to give some more details of results;

2) Sea ice growth: If this is the result of combined effects of sea ice thermodynamics and dynamics, it would be better use the “sea ice thickening”, for item obtained from pure thermodynamic process, it is sea ice growth;

3) Line 310, “the SIT distribution a region” change to “the SIT distribution in a region”;

4ï¼Line330 “the climate mean 2010-2019” change to “the climate mean of 2010-2019”;

5) Line 389 “ocean and sea ice time scales” I don’t understand the time scales here;

6) Line 430 “losing heat the atmosphere” change to “losing heat to the atmosphere”.

Citation: https://doi.org/10.5194/tc-2020-375-RC2
- AC2: 'Reply on RC2', Klaus Dethloff, 27 Apr 2021
  
  The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2020-375/tc-2020-375-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/tc-2020-375-AC2

Peer review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (17 Sep 2021) by Petra Heil

Editor's comments after 2 reviewers:
(Note: In the following manuscript is abbreviated ms.)

In this ms the authors set out to characterize the sea-ice thickness during the MOSAIC winter of 2019-2020, exploring a combination of hindcast model simulation, ensemble runs (both with a regional coupled model) and satellite-derived ice-thickness products. -- A significant amount of work went into conducting the model runs and pulling the datasets together. However, the current ms falls short at the discussion of results and the development of a conclusive argument.

General:
* The line of argumentation in the ms requires strengthening in several sections,
i.e., the section from line 303 - 312. Please check your ms carefully and revise.
* The section "4 Summary and Conclusions" is particularly weak in providing a concise summary and establishing the conclusions of the work reported in this ms. I recommend the thoroughly revise the complete ms appropraitely.
* Suggest to streamline the ms text. In parts it is quite talkative, i.e.,
line 190 "The regional model hindcast simulation was set up in the following way."
* Correct "e.g." to "e.g.," throughout ms.
* Correct "i.e." to "i.e.," throughout ms.
* Correct "in situ" to be in italics.
* Correct "low-pressure" xxx to "low pressure" xxx. I.e., the format used in line 384
"low pressure anomaly" is correct as "low" is not a noun.
* Citations: Be constistent in citation format: E.g., comma or no comma before
" publication year: "(Dethloff et al. 2006; Sokolova et al., 2017)" (l71)
* All figures: Captions and labels are too small. Pls increase font.

Minor:
27: Correct "Barents- and Kara Seas" to "Barents- and Kara seas".
31: "model-simulated sea ice ...": What is "model-simulated"?
59: Correct "Barents- and Kara Seas" to "Barents- and Kara seas".
62: Noun missing in "the wind-driven together": --> "the wind-driven circulation together".
63: Correct "Arctic basin" to "Arctic Basin".
64: The sentence "Therefore, oceanic heat convergence and atmospheric winds appear
as the main drivers of the BS ice cover." is not complete/meaningful: Which
characteristic()s of the ice cover is/are driven?
120: Correct "Nordic Seas" to "Nordic seas".
126ff: Sentence too long and convoluted. Object missing before "was docked to a stable sea ice floe north of the Laptev Sea in October 2019". --> Rewrite.
130: Replace "established" with "observed".
140: Were they "measurements" or "observations", i.e., following ASSIST protocol?
144: Pls provide reference or evidence for the following statement: "regional feedbacks are a function of the background climate state."
152: Suggest to add "observed" to clarify "(ii) diagnose the observed evolution of sea ice,".
153: Siplify "under the influence of a positive AO phase" to "for positive AO".
156-162: Suggest to remove the preview of upcoming chapters.
166: Optional: Spell out "ESA" at first use.
Rewrite for readability: "is based on the ESA CryoSat-2/SMOS Level-4 sea ice thickness data set," to "is based the European Space Agency's [ESA] CryoSat-2/SMOS Level-4 sea ice thickness data set,".
166: Change "produced and disseminated by the ..." to "accessed from the ...".
166: Provide URL for CryoSat-2/SMOS Level-4 sea ice thickness data set.
167: Correct "data is based" to "data are based".
169: Is "gap-less" a word? Change to "resulting in sea-ice thickness information free from gaps".
169: Quantify "with sensitivity", or at least qualify.
174: "sea-ice thickness anomaly" --> Suddenly hyphenation for three or more noun structures are used! Keep it uniform throughout the ms.
174: Change "of this month" to "for each month".
178: Correct "the measurements" to "the measurement principles" (as Haas 1998 and Haas et al 1999 predate the 2019/20 measurements!!!!)
190: Correct "the horizontal direction" to "in both horizontal directions".
222: Correct "Beaufort and Siberian Seas" to "Beaufort and Siberian seas".
224: Improve sentence structure around "whereas over the Western Arctic a high-pressure anomaly existed".
226: "regional cold temperature anomaly": Regional or local?
228: Suggest to change "In March" to "By March".
234: Avoid wording like "are displayed in Figure 3.", as no scientific information contained. Instead use the space to describe the science around the data shown in the figure. Change figure reference to "(Fig. 2)".
234: Provide brief info as to why December 2019 is now shown. What is happening to sea-ice thickness during that month?
242: Rewrite "were a period with the strong positive AO phase." to "were marked by strong positive AO."
242: Avoid terminology such as "Figure 3 clearly indicates". Descrive what and how this is "clearly indicated".
243: Change "(Figure 1)." to "(Fig. 1)."
244: Correct "thermodynamical and dynamical contributions" to "thermodynamic and dynamic contributions".
256: Add "in our simulation" to read "in our simulation occur in the BS".
258: Rewrite "Figure 4 additionally displays the positive SIT anomalies of the Arctic Ocean north-west of Greenland." to "The RASM simulations (Fig. 4) also exhibit positive SIT anomalies of the Arctic Ocean north-west of Greenland, not found in the CryoSat-2/SMOS-derived SIT anomalies (Fig. 3)."
259: Change "in Figure 5" to "(Fig. 5)".
260: Correct "Basin" to "basin".
260: Correct "the Laptev Seas" to "the Laptev Sea".
263: Need to provide the reference to "The differences in SIT".
265: Avoid statements such as "Figure 5 relies". Pls rewrite.
265: Avoid jargon such as "a bit".
266: How can a uncertainty source be expressed as a relative measure? Rewrite "Landy et al. (2020) estimated the principal source of pan-Arctic SIT uncertainty due to variable ice surface roughness in the range of 20-30 %."
267: Avoid statements such as "Figure 5 shows". Pls rewrite.
268: Avoid statements such as "Figure 6a displays"i or "and Figure 6b". Pls rewrite.
271: Avoid statements such as "Table 1 compares". Pls rewrite.
277: Avoid statements such as "are displayed in Figure 7". Pls rewrite.
278: Avoid jargon such as "A closer look shows".
278: Add "2019" to "November 2019".
280: Correct "Siberian Seas" to "Siberian Sea".
282: When discussing results from model simulations avoid terminology such as "is visible" in "weaker sea ice growth is visible". Remind the reader that results of numerical simulations are discussed, not to be confused with observations, which often involve "visual" techniques.
283: Correct "as part of the MOSAiC resupply between" to "undertaken during the MOSAiC resupply voyage between".
284: Correct "between 84°N and 88°N" to "between 84° and 88°N".
284: Avoid statements such as "are displayed in Figure 8". Pls rewrite. -- Instead provide a description of the how observed and modelled ice thickness compare.
288: The reason for the 0.3 - 0.4m underestimate of the ship-based EM-derived ice thickness is not convincing. Please investigate further and revise text based on updated information.
290: Avoid statements such as "Figure 8 shows". Pls rewrite.
292 and throughout ms: Replace "“Kapitan Dranitzyn”" and "“Polarstern”" with their proper names: "RV Kapitan Dranitzyn" and "RV Polarstern" where both, "Kapitan Dranitzyn" and "Polarstern" are in italics.
292: Rewrite "The movement of “Kapitan Dranitzyn” to “Polarstern” in the sectors of the BS of the Arctic basin in February and March 2020 was carried out in great distresses due to severe ice conditions."
293: Rewrite "The most difficult parts of the route went through hummocked thick first-year and second-year ice."
295: Add "2020" to read "February 2020".
295: Rewrite "Separate large leads, which appeared after passing cyclones, were predominantly in the zonal direction."
290ff: Please rewrite this section (to line 301) for clear conveyance of the data and their interpretation/discussion.
Also, avoid statements such as "Figure 9 indicates" and "Figure 9 also presents". A figure cannot "indicate".
298: It is not straight forward to use terminology such as "clear zonal orientation" that close to the pole. Suggest to rewrite and include a reminder for the reader of the relevant MSLP pattern due to the +AO.
305: Replace "connected with" with "related to".
306: Correct "by deformations" to "by deformation parameters"
307: Correct "e.g." to "e.g.,".
307: Correct "that the changes of atmospheric winds can explain 78% of" to "that changes in surface wind stress may explain 78% of".
308: Remove "," after "This confirms,".
308: Replace "atmospheric winds" with "surface wind stress".
308: Replace "ice cover" with "sea ice properties" or "sea ice distribution".
308 - 309: Need to provide stronger reasoning to derive at the conclusion drawn here.
310: Change "can occur" to "may occur".
311: Clean up "can be often determined".
313: Avoid statements such as "Figure 10 displays". Pls rewrite.
313 ff: Please explain what exactly is shown in the top left and right sub-figures of Fig. 10. How is the convergence anomaly different than the divergence anomaly? Pls include full information for the reader.
315: Clarify what is meant by "The sea ice drift is a result of the near surface wind fields, which determines sea ice deformation." This is not a novel finding... Rewrite to improve text flow and provide reference.
316: Rewrite "Sea ice momentum changes are a result of combined air-ice and ice-ocean stresses." for better text flow and provide reference.
318: Remove hyphen in "Fram-Strait".
321: Remove "values" from positive ice shear values".
323: Verb is singular but noun is plural in "whereas ice shear processes due to wind stresses indicates here positive anomaly values". -- When rewriting, focus on the information you need the reader to take away
324: Rewrite "This leads to the conclusion... or deformation.", especially at "are largely influenced and a result of wind stresses".
326: Correct phrase "Atmospheric near surface wind advection".
326: Avoid statements such as "displayed in Figure 2". Pls rewrite.
327: Rephrase "These wind components".
328: Change "in JFM 2020 could" to "during JFM 2020 may".
329: Change "and Inoue" to "or Inoue" with "or" not in italics.
332: Avoid statements such as "Figure 11 presents". Pls rewrite.
332: "climate mean" or "climatic mean"?
333: Need to clarify which quantity is "computed from OSI-SAF low resolution sea ice motion data". Unclear with the current syntax.
336: Avoid statements such as "both displayed in Figure 2." Pls rewrite.
337: Add "2020" to read "In March 2020".
338: Expand to provide info on the advective process of thickening the ice thickenss (and where).
340: Change "connected with" to "related to".
340: "which affecting the ice divergence/convergence.": Correct to use the correct conjugation.
341: What is this? "model-based drift sea ice velocity anomalies" -- A string of nouns that does not make sense. Please rewrite.
342: Correct "Eastern" to "eastern". I.e., "Western Arctic" but "the western part".
342: Correct "Western" to "western".
342: Avoid statements such as "displayed in Figure 11". Pls rewrite.
343: Remove "strength of" as "drift" is a scalar so only its amplitude or strength can change.
343: Avoid colloquialism such as "differs a bit", pls rewrite. Also add to strengthen discussion of your results.
347: Please rephrase the term "internally generated climate variations".
349: Rephrase "under the remote AO impact in ensemble forecasts".
350: Avoid statements such as "Figure 13 displays". Pls rewrite.
355: Shorten by removing "ice volume" from "negative ice volume departures".
363: Avoid statements such as "we display ... in Figure 14". Pls rewrite.
365: Correct "varies" to "vary".
367: Correct "remains similar strong" to "remains similarly strong".
367: Use consistent nomenclature, i.e., write "November 2019-February 2020" and "in March 2020".
Apply similar consistency in nomenclature thoughout the ms, i.e., lines 368, 371 etc.
373: Avoid statements such as "Figures S3, S4 and S5 show". Pls rewrite.
374: Avoid statements such as "These figures clearly indicate". Pls rewrite.
382: Avoid statements such as "Figure S6 displays". Pls rewrite.
388 - 391: Need to clarify and expand the argument to draw the conclusions described here.
392: Avoid statements such as "Figure 15 displays". Pls rewrite.
396: Correct "Laptev Seas" to "Laptev Sea".
396: Rephrase "The difference plot indicates differences"... and avoid a "plot indicat"ing something, pls.
401: Correct "Compared to" to "Compared with".
401 - 403: Not sure if this interpretation is correct: All ice edge regions appear to exhibit similar peak differences (as seen in Fig. 15). Please discuss this.
402: Change "both presented in Fig. 15" to "(Fig. 15)".
411 - 413: The list of feedbacks is rather long.
413 - 415: The discussion of regional forcing and Earth System connectivity versus hemispheric or global requires further discussion. The currect ms exposes issues but does not test nor resolve them.
415: Correct "Greenland Seas" to "Greenland Sea".
416: Avoid statements such as "Figure S8 shows". Pls rewrite.
418: Avoid jargon. Rewrite "allows a rough and quick diagnosis" to "allows an efficient albeit coarse diagnosis".
420: Avoid statements such as "Figure 16 presents". Pls rewrite.
420: Remove "period".
422: Correct "Beaufort-" to "Beaufort" and "Seas" to "seas".
426 - 427: Reference required for "During winter.... current occur." -- Also this statement requires some rephrasing and integration into the discussion.
428: Avoid statements such as "Figure 16 displays". Pls rewrite.
439: Correct the phrase "the transport of warm air and humid".
441: Avoid statements such as "Figure 16 supports the view". Pls rewrite.
441 - 442: Rewrite and expand the argumentation.
442: Add "Sea" after "Greenland".
444: "sea-ice thickness --> There it is again: Hyphenation for three or more noun structures are used! Please keep it uniform throughout the ms.
444: Remove "information" after "sea-ice thickness".
444: Correct "remote sensing data" to "remotely sensed data".
444: Shorten "based on the ESA CryoSat-2/SMOS Level-4 sea ice thickness data set".
444: "sea ice thickness --> Two different ways in the ONE sentence to apply hyphenation rule! Please keep it uniform throughout the ms.
445: Move "produced and disseminated by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research" into the acknowledgement.
447: "satellite sea ice thickness measurements": This ice-thickness product is derived, not "measured". Rephrase.
450: Remove "the period with a".
444 - 452: There appears little new information from one sentence to the next in this section. Pls rewrite in a more concise and best more investigating way.
452: Correct "the Laptev Seas" to "the Laptev Sea".
458: Remove hyphen from "In-situ" and show in italics.
Also: Were the measurements on „Kapitan Dranitzyn“ in situ measurements? My understanding is that an EM instrument was used.
460: Correct the tense in "In January 2020 strong ice growth takes place".
461: Correct "Siberian Seas" to "Siberian Sea".
461: Add "2020" to read "In February 2020".
461: Correct the tense in "anomalies occur".
461: Why change from "in" to "over? --> "over the Beaufort Sea"?
462: Add "2020" to read "in March 2020".
462: Why change from "in" to "over? --> "over the mid-Arctic Ocean"?
463: Replace "weaker" with "less".
463: Avoid the phrase "is visible".
464: Change "connected with" to "related to".
464: Remove "the" from "the colder temperature anomaly"... and there is no such thinkg as a "colder temperature anomaly", pls rephrase.
465: Correct grammar of "ice shears".
465: Correct "Compared to" to "Compared with".
468: "model-simulated": What other similations are there in context of this ms? Pls rephrase.
470: "processes" is plural, but the verb "indicates" is for singular. --> Correct.
472: Check the tense of "and accelerating".
473: Remove hyphen from "low-pressure".
475: Correct "indicates" to "indicate".
476: Correct "November until January." to "November 2019 to January 2020."
477: Rephrase "could contain a strong portion of" to "may indicate".
478: Remove "-generated climate" to read "internal variability".
479: Rephrase "diverging temporal evolution" and "we display".
481: Suggest to change to "the Pan-Arctic and the BS domains".
482: Change "internally generated variability" to "internal variability".
484: Add "2019" to read "December 2019".
485: Change "wind advection" to "atmospheric advection".
486: "accumulated" or "intergrated"?
489: Correct "Seas" to "seas".
494: Correct "Seas" to "Sea".
494: Change "wind advection" to "atmospheric advection".
503: Remove "in Reading".
504: Correct "was produced" to "were produced".
554: References:
--> Not checked in this review.
Tab. 1: Is the correct syntax "decimal point" or "decimal comma"?
Show the unit for the S.D.
687: Correct "for November 2019 until March 2020." to "for November 2019 to March 2020."
704: Correct "[December 2020]" to "[Deceber 2019]".
704: Provide explanation why December 2019 is not shown.
Fig2: (or another suitable): Label the various ocean basins and other relevant locations in an early figure.
Fig5: Remove redundant subcaptions: ": CS2-SMOS SIT"; "RASM SIT", and
"CS2-SMOS minus RASM".
Fig7: Remove redundant subcaptions:
"RASM Hindcast ice-growth (m/month) for";
"RASM Hindcast ice-growth Anomaly (m/month) for";
"RASM Hindcast ice-growth Anomaly (%) for";
759: Replace "with the maximum" with "at the highest".
760: Explain on which basis leads have been identified in teh VIIRS image. Please do this in the paper itself rather than in the figure caption.
761: Fig 9b: Specify if instantenous RASM divergence is shown. Include relevant information on any data manipulation for the divergence shown here.
783: Change "Anomalies" to "RASM anomalies".
785: Add note as to what sea-ice drift distribution is shown in all 3 sub-images, i.e., for which time.
Fig11: Label of 2nd sub-figure: Include source the "Sea ice velocity anomaly" in the title label.
Fig11: What is the relevance of the AWI Meereisportal.de logo on the sub-figure?
Fig11: Pls present both colourbars in the same arrangement and with same text font and size.
Also: Captions and lables: Use fame text font and size in each sub-figure.
Fig11: If not too much time required: Use the same colourscheme for the "sea ice velocity anomaly" sub-figures.
FigS6: Correct typo in title of 2 left-most sub-figures from "Haindcast" to "Hindcast".

Hide

AR by Klaus Dethloff on behalf of the Authors (26 Oct 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (22 Nov 2021) by Petra Heil

RR by Anonymous Referee #1 (04 Dec 2021)

Suggestions for revision or reasons for rejection

Generally, the manuscript is revised greatly following those review comments, and becomes acceptable to “The Cryosphere”.

I still have some additional minor comments:
Thank you for revising the alignments or size of those figures 2, 3, 4, 5, 7, 15 and 16. However, I am still not convinced by the coordination of some figures. As you mentioned in the reply, Figs. 10 and 11 are difficult to revise. But couldn’t you make the scale and direction identical for the two plots in Fig. 11? Also, why only the coordinates of Figs. 3 and 12 are different from most of the other figures (Figs. 2, 4, 5, 7, 15, 16)?
Figure 2 is still complicated in alignment, and difficult to follow. It's better to show SLP and 2 m temperature anomaly for all four months, November 2019, January, February and March 2020, just as other Figs. 3, 4 and 5. Why you didn’t show 2 m temperature anomaly for February and March 2020? Temperature anomaly in March is discussed in the text (LN 294).

Generally speaking, supplement figures should be “Supplement”, so, the mainstream of the text should stand without supplement; however, this manuscript uses supplement figures at several places to explain (especially in sections 3.1 and 3.2). In that case, the supplement figure should be included in the main text. We could not follow the story without supplement at the present configuration. Mostly, supplement figures should be used to support the text description.

(Specific comments)
- LN 251: PDFs should be written down at the first appearance.
- LN 291-295, Fig. S4: Low surface pressure in mid-February and high pressure at the beginning of March are anti-correlated with 2 m temperature; however, low pressure in the mid-March (similar to the mid-February case) has no exact relation to 2 m temperature, and no explanation was made to this term.
- Fig. 8: The ranges of the two axes of the left plot are two small, so that makes the deviation emphasized. If you make the range much larger, then the impression might be better, not so large deviation.
- LN 429: “reduced convergence” should be “reduced divergence” or just “convergence”.
- LN 796: The second “Nakamura T.” is duplicated.

Hide

RR by Anonymous Referee #3 (15 Dec 2021)

ED: Publish subject to minor revisions (review by editor) (21 Jan 2022) by Petra Heil

(Note: In the following manuscript is abbreviated ms.)

I thank the authors for submitting a revised version based on previous reviewer's and editor's comments.

In this ms the authors set out to characterize the sea-ice thickness during the MOSAIC winter of 2019-2020, exploring a combination of hindcast model simulation, ensemble runs (both with a regional coupled model) and satellite-derived ice-thickness products.

General:
Although in their response the authors indicate having addressed most (editor's) comments, it appears that the following have been overlooked. Kindly tend to those in preparing the next ms version:
* The line of argumentation in the ms requires strengthening in several sections,
i.e., the section from line 407 - 416. Please check your ms carefully and revise.
* The section "4 Summary and Conclusions" is particularly weak in providing a concise summary and establishing the conclusions of the work reported in this ms. I recommend the thoroughly revise the complete ms appropriately.
* Correct "e.g." to "e.g.," throughout ms. For example: Lines 47, 51, 80, 474, 475.
* Correct "i.e." to "i.e.," throughout ms. For example: Lines 30, 208, 366, 943.
* Correct "in situ" to be in italics. For example: Line 144.
* Correct "RV “Polarstern”" to "RV Polarstern" (with "Polarstern" in italics).
* Correct "“RV Kapitan Dranitzyn”" to "RV Kapitan Dranitzyn" (with "Kapitan Dranitzyn" in italics).
* Correct "low-pressure" xxx to "low pressure" xxx. I.e., the format used in line 384
"low pressure anomaly" is correct as "low" is not a noun.
* Citations: Be constistent in citation format: E.g., comma or no comma before
" publication year: "(Dethloff et al. 2006; Sokolova et al., 2017)" (l71)
* Most figures: Captions and labels are too small. Pls increase font.

Minor:
240: Move the data source "https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml" into the section "Acknowledgement" section

* Suggest to add an acknowledgement thanking the reviewers for their effort on this ms.

23: Remove "period" to read "for the three-month JFM2020".
25: Remove "the time period from" to sharpen the sentence.
27: Capitalize "Sea" in "Barents sea (BS)" as "Sea" is here a name label. On the other
hand "seas" in "Barents and Kara seas" is lower case as "seas" is a collective descriptor.
29: Correct "cold" to "low" to read "low temperature anomalies".
30: Correct "i.e." to "i.e.,".
59: Correct "Barents- and Kara Seas" to "Barents- and Kara seas".
95: Correct "Nordic Seas" to "Nordic seas".
567: Correct "Nordic Seas" to "Nordic seas".
134ff: Sentence too long and convoluted. Object missing before "was docked to a stable sea ice floe north of the Laptev Sea in October 2019". --> Rewrite.
194: Change "of this month" to "for each month".
253: Change "This circulation is connected with atmospheric 10 m winds" to "This pattern of near-surface atmospheric circulation coincides with low-level (10m) winds"
254: Change "and warm air masses inflow" to "and with inflow of warm air masses".
255: Change "and a" to "paired with a".
273: Change "the AD pattern appears as third EOF" to "the AD pattern manifests itself as the third EOF".
277: Correct "the AO index remain" to "the AO index remains".
278: Change "over the whole period" to "from".
284: Correct "for the time period 2005-2020" to "for 2005-2020".
286: Correct "occur in the time period January-March 2020" to "occur during January-March 2020".
286: "a low surface pressure anomaly is determined by a strong synoptical cyclone event": Do you mean "is driven"?? Unclear.
299: Correct English "was positively offset compared to".
300: Correct "but only prompted the transpolar drift to pause" to "instead slowed".
302: Change "hinting at a looser ice cover" to "suggesting a less concentrated sea ice".
303: Poor terminology "A close relation". Substitute with "A covariability" or similar.
304: Text is "is visible" but no supplementary figs included.
303-307: Text is too long and not evidence based. It is a narrative. --> Rewrite.
312: Correct "At the Bering Strait" to "In the Bering Strait".
312: Correct sentence "In December 2019 (not shown) already weak sea ice anomalies to start
develop in the BKS." to "As early as December 2019 (not shown) weak sea ice anomalies
develop in the BKS."
320: Correct "thermo-dynamic" to "thermodynamic".
333: Correct "Siberian Seas" to "Siberian Sea".
344: Correct "data is dominated" to "data are dominated".
377: Suddenly there is a hyphenation of a 3noun sequence: "sea-ice regions" --> Be consistent!
385: Correct "over the Beaufort and Chukchi Sea" to "in the Beaufort and Chukchi seas".
395: Please change to more technical wording: "However, RASM results would agree very well with observations, if ~0.4 m were added to the ship-based data."
398: Correct "Arctic basin" to "Arctic Basin".
405: Add "(Fig. 9, right panel)" after "from the RASM simulations".
405: In Fig. 9, RHS: The divergence pattern near the pole appears to be aligned with model grid cells. Have you explore the reason for this? Include here?
406: Add fullstop at end of sentence.
407-416: The explanation provided here is rather qualitative. Pls tighten the argument here, and use more precise wording.
419: Correct "Longer black arrows" to "Longer vector (black)".
424-438: This paragraph is rather wordy. Pls shorten and sharpen the line of argument.
Need to consider that Fig. 10 shows data mean for 3 month .
453: Change "induced a stronger drift towards the BS" to "strenghtenend the drift toward to BS".
466: Improve language to clarify: "but then it was forced by a different, 24-hr apart, NCEP Climate Forecast System (CFSv2) global forecast initialized 24-hr apart at 00.00 between 1st and 31st October 2019."
480: "volume tendencies": Need to provide a sound (but precise, aka brief) introduction to their definition and how to interpret these to carry forward the next page of argumentation.
496: "However, those two ensemble members are not representative of the BS,": Provide evidence why.
481-526: This section is rather quantitative and broad brushed. Is there a metric that captures the underlying TD vs Dyn argument?
551: Correct "Beaufort-" to Beaufort".
556: Clarify sentence: "connected to the North Atlantic oceans current occur."
555-571: Suggest to sharpen the existing text. Also add a paragraph on how this change in energy budget affects the balance between TD and Dyn ice-growth rates. Consider adding a figure.
627: Correct "Beaufort-" to Beaufort".
635: Correct "Norwegian Seas" to "Norwegian Sea".
637: Change "which needs more in-depth investigation." to "which calls for in-depth investigation."
663: "Codes or data are available form the authors by request." --> Ensure that this meets policy of the journal.
Conclusions (573-637): These seem to remind the reader of findings from individual analysis carried out for this work, but lack the overall summary of the identified drivers for the sea-ice conditions during MOSAIC in winter 2019/20. Strongly suggest to review this section and include a conclusive finding based on the results provided in the paper.

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AR by Klaus Dethloff on behalf of the Authors (30 Jan 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (13 Feb 2022) by Petra Heil

AR by Klaus Dethloff on behalf of the Authors (14 Feb 2022) Author's response Manuscript

Short summary

Sea ice thickness anomalies during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) winter in January, February and March 2020 were simulated with the coupled Regional Arctic climate System Model (RASM) and compared with CryoSat-2/SMOS satellite data. Hindcast and ensemble simulations indicate that the sea ice anomalies are driven by nonlinear interactions between ice growth processes and wind-driven sea-ice transports, with dynamics playing a dominant role.