Sediment Waves on the Western Slope of the Chukchi Rise (Arctic Ocean) and Their Implications for the Paleoenvironment

Round 1

Reviewer 1 Report

GENERAL COMMENTS

The manuscript embraces a very interesting hard-to-reach polar region. The work is based on high-quality data and focused on a very important topic (which is of big interest for the contourite community and for me personally).  I think this manuscript is acceptable after major revision. My comments are given below.

I suggest slight changes in the title and structure of the paper:

SEDIMENT WAVES ON THE WESTERN SLOPE OF THE CHUKCHI RISE (ARCTIC REGION) AND THEIR IMPLICATIONS TO MODERN- AND PALEOENVIRONMENT

INTRO

METHODS

-        Multibeam bathymetry

-        Sub-bottom profiling

RESULTS

-        Echo character types and distribution

-        Location, morphology and acoustic structure of sediment waves

DISCUSSION

-        Sediment wave formation

-        Implications to paleooceangraphic environment

CONCLUSIONS

----------------------------

Only one echo character type was described in the work. The other types were neither described nor discussed. However, authors put the interpretation of some echo characters as hemipelagic and glaciogenic deposits in Fig. 4. What factors control the lateral distribution of echo characters and acoustic penetration in the study area? If glacial sedimentation has become dominant in this area since the Quaternary (row 61-62), why sediment waves were not buried/draped (at least partly)?

The bedform-velocity matrix which authors used to estimate paleocurrent speed is based on both bedform morphology and sediment grain-size. As I understood the authors estimate the grain size of the deposits composing the sediment waves. The source of the grain-size data used in this work is not clear.

It states that the studied sediment waves show clear upslope migration. It is true only for the lowermost part of the seismic section (Fig. 4). I can’t see it in the upper part. Does it mean that the current speed and direction (bottom circulation regime/sedimentation mode) varied during the period of wave formation?

I am not a native speaker, but nevertheless I suggest that the manuscript needs English editing and proofreading.

 

SPECIFIC COMMENTS

ABSTRACT

19-20 “well-layered hemipelagic deposits in tens of meters thickness were affected by 20 sediment wave…”

The term “hemipelagic deposits” implies the dominance of the vertical sedimentation, while the presence of sediment waves points to the prevalence of lateral sedimentation. Why do authors suggest that the studied deposits are hemipelagites? (however, in row 22 these deposits are called contourites)

21: “morphological characteristics” instead of “bathymetric”

23: I would suggest to use the more general term “bottom current” (according to definition from (Rebesco and Camerlenghi, 2008)) instead of more specific “contour current”

KEYWORDS

I do not recommend using words mentioned in the title as keywords

INTRODUCTION

28-30: please, just use the definition Wynn et al. (2000) with slight modifications “a large-scale (generally tens of metres to a few kilometres wavelength and several metres high), undulating, depositional bedform that is generated beneath a current flowing at, or close to, the seafoor”

“large-scale seabed morphology”, “stretch from tens of meters…” sound not good in this case

36-37: “developmental characteristics”,  “with local background data” – please explain in the topic context

36-41: Please, correct this sentence and split it in several smaller phrases. I did not fully understand what authors tried to say in this text.  

51-52: “the deepest depth” sounds not good. Maximum depth is better

56: “contour” instead of “isobaths”

METHODS

MULTIBEAM, PALEOCEANOGRAPHIC, UPSLOPE – please, use these terms WITHOUT DASHES – please fix throughout the text

100: Please change the section title as following: “Sub-bottom profiling”

103: Please explain, what “FM” means?

RESULTS

139: “extension length” sounds not good. Wave crest length is better. Please indicate that this parameter value exceeds  … km (beam width)

154-156: “The line connecting the wave crests of each reflection interface of the sediment wave is slightly inclined toward the downslope, indicating that the sediment wave has the characteristic of up-slope migration.”

It is true only for the lowermost part of the seismic section. I can’t clearly see it in the upper part. Please, draw these lines in Fig. 4.

Upslope – without a dash

 

FIGURES

FIGURE 1

What solid yellow lines mean? One of them runs out of the image borders. And solid blue line? And small red circle?

The location of the study area should be shown in a more general map with coast lines/continents (as an inset). It is not clear for a reader who is not familiar with the region, which part of the Arctic is it?

FIGURE 2 and 4

Indication of cardinal points is needed to understand the orientation of the profiles.

FIGURE 3

This figure is very important, but parts b and c are too small. All the parts of the figure should be aligned as a column. It helps to enlarge the b and c parts on the “album-oriented” page.

FIGURE 5

 

What red dots mark?

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript is well presented, and the research topic is of interest.

The survey performed was made with up-to-date technology.

There is some mistake in the title; probably, the last word should only be "Environment".

Unfortunately, there is too much uncertainty in the results, i.e. the authors speculate instead of trying to improve the knowledge regarding sand waves.

I understand that it is difficult to elaborate based on a single survey, but some information that could be included for correlation, such as waves, tides, and storms, may have enhanced the discussion and conclusion.

The title announces implications for the modern environment, but these are not included in the manuscript.

The sub-bottom profile data seems to provide interesting information on the sand wave structure, but it is not exhaustively used in the manuscript.

I think that if the authors can improve the manuscript and work on turning it into a journal paper and not a report of a survey, I can recommend it for publication.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 3 Report

 

The manuscript is well written with pleasant text to read and the information is very objective. The topic is very interesting and brings an excellent scientific contribution that will serve as a basis for more detailed studies. The text has good references, but could be improved. The methodology is clear and well applied. Few modifications are needed to improve the manuscript:

In line 58, where it has Fig.1, this is not clear whether it is (Fig 1a) or (Fig1b). Could it be Fig.1a? I believe it is Fig.1a

In Fig 3a and 3b it’s difficult to read the profile values, I suggest improving this figure

In line 138 speaks of Fig. 2c, this is not clear what that figure would be? I suggest reviewing description of all figures in the text before the article is accepted.

In line 196, it speaks of a thickness greater than 50m in Figure 4. I don't see a thickness scale in this figure. Still in Figure 4, the profile zoom can be called Figure 4b.

Figure 5 has the names in blue and green that are impossible to read. I suggest fixing this figure before being accepted.

 

I believe that after a further detailed review by authors and corrections of some figures and text in English, the article will be ready to be accepted

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Authors significantly improved the manuscript. However it still needs some corrections. I provide my comments below: It states that the revealed sediment field is large, but the presented data are not sufficient to confirm it. The large fields of sediment waves cover thousands of sq.km (e.g. in the Argentine Basin). In the context of this work the fact of sediment wave occurrence is important itself. “sub-bottom” instead of “subbottom”, please make corrections throughout the manuscript 50: please delete “seabed” 78: "drilling site" instead of "geological core" 132: please, delete “shallow” 133: meters instead of m 136-138: I consider this not results but discussion (interpretation of sub-bottom profiling data). Please, do not mix results and discussion. 154-165: This part should be moved to the Discussion section. This paragraph mainly includes interpretation, not the description of the results. The RESULTS chapter should contain a minimum of references and should be focused on the description of the results obtained by authors. 188: this section should include the description of the new non-published results. If this information was previously published, so the sentence should be moved to the intro, regional settings or discussion. 226: “cruise” instead of “voyage” 236-247: LADCP measurements should be described in methods, these lines should be moved to results. Additional section on hydrological data should be added to the results. 306-307: I would not recommend using the word “weak” for the characterization of the current speed in this context. Fig 1. There is a pink solid line (arrow) on the figure. Should it be dotted, if not, please specify the meaning of this sign.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

I see that the authors considered all of my comments and that they included information in the manuscript consequently.

I still think that the marine conditions, specifically marine currents, may provide valuable information to understand the sediment waves under study as they are still active, as stated in the research.

Also, the word "speculation" is commonly avoided in engineering journals. This may be a matter of discipline-specific use of language.

Given the improvements in the manuscript, the response to the comments and the inclusion of supplementary material, I can recommend this work for publication.

Author Response

Please see the attachment

Author Response File: Author Response.docx