Dear authors
Thank-you again for your revised manuscript. I now have comments from both original referees, see below. I also had some detailed Editor comments of my own which I hope I sent you; anyway, they are repeated below. Please take all these comments into account in “minor revision” meaning that I will take a last look myself but do not expect to call on the referees again.
Yours sincerely
John Huthnance


Referee #1
Review of revised manuscript “Influence of Estuarine Tidal Mixing on Structure and Spatial Scales of Large River Plumes” by Osadchiev et al.

General comments
The manuscript describes using in-situ salinity observations and satellite data (turbidity, temperate and chlorophyll-a) to study the spatial scales and contrasting structures of two river plumes in the Arctic Ocean.
In this revision, the authors have addressed my comments on their original manuscript by omitting discussion that was not substantiated by their data and including a summary of the differing tidal climates of the two gulfs. The addition of satellite data to support identifying the extent of river plumes strengthens the manuscript.

Specific comments
Caption to figure 1 is repetitive and could be shortened.
Line 119 onwards (or elsewhere) please include information on how the satellite data are used to identify plume extent (what makes these quantities suitable and what range of values denote plume/ocean boundaries?)
Line 127 used -> use
Line 132 performed -> measured
Line 137 please clarify: was each year of tide gauge data analysed?
Caption to figure 2: please include details of the time period considered.
Caption to figure 3: the last sentence is repetitive.
Figure 8a: is it possible to change the colour scale and increase the contrast; the difference between plume and ocean water is not very visible?
Lines 388-389 and 455: you have shown that the extent of the limits of two river plumes from their gulfs is similar but not assessed areas or volumes of the plumes.


Referee#2
The revised manuscript is by and large ready for publication.

I still disagree with the authors on their interpretation of the offshore extension of the plume, and my point is further supported by satellite images presented in the revised version: the axis of the Khatanga Gulf runs from southwest to northeast, and the buoyant water creeps along the northern coast of the gulf toward the Laptev Sea. Figures 9 and 10 give a very clear picture of this process. What the authors perceive as the offshore extension is really a meridional distance from the southern coast to northern coast of the gulf (where the buoyant water resides). However, I will leave this to the Ocean Science readership.

Showing vector time series as two panels, velocity magnitude and direction, is difficult for interpretation. I think u- and v- components would be more readable (and the reader does not have to worry about the atmospheric vs oceanographic notation for the direction).

Tidal analysis (lines 137-144): do those 68 tidal constituents include overtides (multiple tidal harmonics)? Tides should be nonlinear in this type of environment, so it would be an interesting piece of information.

There are a few awkward expressions throughout the text, here are some examples (this is not intended as an exhausting list):
Line 41: “…estuaries… flow into the Arctic Ocean”. Estuaries don’t flow, freshwater discharge does.
Line 140: “We revealed that tidal circulation…”
Line 222: “…salinity… was relatively stable….”
Line 326: “hydrological stations” (hydrographic stations?)


Detailed Editor comments
Line 23. “that” -> “as”
Lines 65-66, 79-82. This information about tides appears in more detail in section 3.1.
Line 82. “which are described above”. This clause presumably refers to the gulf and straits, and seems unnecessary. If the references on line 83 are for the tidal velocities, they should not be separated from the rest of the sentence by “which are described above”.

Line 90. Better “ship-board”
Line 91 end. “conductivity” (spelling)
Lines 103-105. You could just refer to the figures and not the red stars and numbers which repeat the figure caption.
Line 107. “version 2018” but none of the references is as recent as 2018. Does the link in the Acknowledgements give access?
Line 117. “far” is unnecessary but it would be helpful to replace it by “upstream” (presumably).
Line 122. Is there a reference for “ESA BEAM”?

Lines 148, 149. “large” -> “larger”
Line 176. “eight”? There are only four in the table.
Line 178. “small” -> “large”
Lines 180 and 435. “extremely intense” is exaggerated. Even Khatanga Gulf is not well-mixed but some outflows are.
Figure 2 caption. “Simpson-Hunter” (reverse order)

Lines 237-238. A referee commented that this calculation does not allow for varying width of the estuary. You responded that this would be pointed out in your text but I don’t see this??
Lines 219-225 and 240-242. Some repetition (does not matter too much but you might like to think about rearranging this section and similarly for the Khatanga plume).

Lines 299-300. The freshwater runoff values here are wrong (much too small).
Lines 332, 438, 448. “on the opposite” -> “however” or “on the other hand”

Lines 365-366. It occurs to me that these references might have evidence about the expected (lack of?) effect of the winds (as discussed in 3.2) on the plumes.
Line 379. “strained” -> “strain”

Lines 438-439. “limitedly affects estuarine” -> “causes only limited”
Line 442. “low-intense” -> “weak”
Line 445. Better “. . propagated from the estuary and spread in the open sea. . .”
Line 450. “inflow” -> “flowed”
Line 453. “low” -> “small”
Line 454. “low” -> “weakly”
Line 463. “presume” -> “infer” and line 465 “assumption” -> “supposition”

Dear Authors
Thank-you for your re-revised manuscript. Please see the “Technical Corrections” below. After attending to these, please upload for final publication in Ocean Science (no more intervention by me). The manuscript will be copy-edited; please check that your intended meaning is kept.
Thank-you for publishing in Ocean Science.
Yours sincerely
John Huthnance

Technical Corrections

Figure 3 caption, line 2. Insert (b) at end of sentence.
Line 200. “more low” -> “smaller
Figure 4 caption, line 3. Insert (b) at end of sentence.

Lines 239, 255, Figures 5c, 6c. I think you should add the caveat that these total freshwater fractions are not strictly volumes because the calculation can only be based on the measured section along each estuary and cannot allow for values elsewhere across the (varying) width of the estuary. (This was a referee comment which will be accessible on final publication. The figure captions are more “honest” than the main text in this respect).

Lines 270-271. This sentence might better read as “The meridional transects from the Ob and Yenisei gulfs in July 2016 (Fig. 7a) gave two crossings of the northern boundary of the Ob-Yenisei plume.”

Line 363. Please explain β better. It is the coefficient of density increase with salinity.
Line 364. Likewise C_D is the quadratic drag coefficient.

Lines 375, 392, 446. Why “anomalously”? With only two plumes it might equally be the Yenisei plume that is “anomalous”. I think this might be justified if you can say that most rivers flowing into the Arctic have weak mixing like the Yenisei.

Lines 382, 383, 387. Better omit “volume” c.f. comment above on lines 239, 255.

Line 456. “. . intensity of estuarine . .”