Mean Seasonal Sea Surface Height Variations in and around the Makassar Strait

Round 1

Reviewer 1 Report (Previous Reviewer 4)

Below are some detailed suggestions, BUT as I said in my review of the previous version of this paper, it cannot be published without serious error analysis, plots showing error bars to make it clear whether the variations and, hence, correlations are significant. 

General:

1. The font in the figure legends needs to be larger. 

Specific:

L 145: Something more explicit about how the Gaussian filtering is done needs to be said.

Fig 3: The points in these plots need some indication of error/variation/uncertainty.  This is particularly important for 3b where the difference will effectively magnify the errors.

L 262: “Remind” -> “Note” or a similar word.

Fig 6: A legend for the colors rather than the text would be much better.  The difference in size between the symbols is not at all obvious.

Fig 7: Include the letters of the points in the legend.

LL 358-374: Given the result in eq 5, I do not see the point of the calculation, discussion in these lines.

LL 383-414: Why not calculate the phase with respect to the monsoon WITH AN APPROPRIATE ERROR BAR and see if there is a meaningful result.

Author Response

Please see the attached pdf file.

Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

This paper explores seasonal variations in currents and sea surface height (SSH) in the Makassar Strait and its surrounding areas, utilizing Jason-series altimeter observations. The study investigates the connections between these variations, monsoons, and the differences in sea surface height between the two oceans, shedding light on the intricate interactions within the region.

A notable aspect of this research is the use of 17 years of along-track Jason altimetry data with the ALES coastal retracker, which offers advantages over gridded SSH products in coastal regions by avoiding grid interpolation limitations.

The findings reveal that SSH variations in the area, spanning from the southern Celebes Sea to the northern Java Sea through the Makassar Strait, are in phase, suggesting a coherent and interconnected pattern of behavior. These variations' amplitudes diminish with distance, generating pressure gradients that likely result from wind-driven transports, as posited in the paper.

An interesting observation is that wind-driven SSH variations are balanced with the bottom friction of the upper-layer ITF (Indonesian Throughflow) velocity, rather than wind stress. This specific dynamic balance plays a pivotal role in influencing SSH variations in the Makassar Strait region.

However, the current draft has several shortcomings that should be addressed. The abstract lacks specificity and detail, and some tables contain "multiple" tables, which is atypical for a journal like Remote Sensing. The figure captions are unclear, and the legends lack definitions, with insufficient resolution in most cases. The presence of numerous highlighted texts also requires clarification.

The methodology explanations are limited, particularly regarding the data analysis process and how conclusions were derived. Expanding on the data processing and analysis techniques would enhance the study's clarity and credibility.

The paper also contains ambiguous language, such as the statement about amplitude and pressure gradients, which could be clarified with more specific language and elaboration.

Furthermore, the paper should offer more context and background information on the significance of issues with gridded SSH products in coastal areas and their impact on previous research in the field. Providing a brief explanation of the limitations of existing approaches would help readers better understand the study's contributions.

Considering these shortcomings, I cannot recommend the paper in its current form.

Comments for author File: Comments.pdf

The English is fluent. 

Author Response

Please see the pdf file.

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Summary

This is an interesting paper with important new results using coastal altimetry processing to allow an analysis of variability in Sea Surface Height not previously possible from satellite altimeter data.

The methodology and analysis are well-described, and the language is clear throughout.

General  points

Section 2: Material and Methods

The paper is specifically investigating seasonal variability, and so the SSHA data have been filtered to extract near-annual variations by removing  variations longer than 13 months and shorter than 10 months. Nonetheless, it would be interesting to see a spectral analysis to establish what percentage of the observed variability is seasonal, and what percentage occurs on shorter (and longer) timescales.

Specific comments

1.     P7 line 245. “Note that the bottom friction coefficient r is not a determinant value, so that the fraction of ris inductively determined in Figure 5, keeping its typical order of magnitude”.

A little further detail and explanation would be useful here. It would be useful to refer to other literature as to expected values of the bottom friction coefficient r, and to provide details on how r has been “inductively determined”

2.     Use of “remind” at various points in the manuscript. P8, line 262; P14 line 435; P15, line 476. “We recall”, or “The reader is reminded” would be a better choice.

Author Response

Please see the pdf file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report (Previous Reviewer 4)

No comments - Good use of coastal altimetry product. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This paper provides insight into the seasonal sea surface height (SSH) variations in Makassar Strait, which can be used to understand and predict oceanic currents. 1. The results of this study suggest that monsoon seasons have an effect on SSH variation within the strait, with increasing amplitudes towards south. 2. It also suggests a balance between pressure gradient along-strait and bottom friction from Indonesian Throughflow over shallow areas in the strait. 2. These findings could help inform future research related to climate change or other environmental issues affecting these regions as well as aid navigation through them for ships travelling across oceans.

In the manuscript, the standardization of article drawings, tables and references should continue to be strengthened. Meanwhile, the highlights in the manuscript need to be further clarified.

Reviewer 2 Report

The article, Mean Seasonal Sea Surface Height variations within the Makassar Strait, study the mean seasonal SSH variations within the Makassar Strait. A good point of the research is the use of along track rather than gridded altimeter data to study the SSH variation in a narrow strait. The seasonal SSH variations in the Makassar Strait and its relationship with surrounding oceans are then well interpreted.  The manuscript is well structured and comes with understandable and supported conclusions. I only have few minor comments:

1.     Section2: It is better to clarity whether ALES retracker data is SSH (absolute sea surface height) or SSHA (sea surface height or sea level anomaly). If the former, what kind of Mean Dynamic Topography data is used?

2.     Lines 181-182: the authors conclude that “the steric height is less dominant in the Makassar Strait”. This mean the seasonal variation is dominant by the change of water mass. Is it possible to verify the contribution of MASS part through the GRACE observation?

3.     Line 197: “kgm3” to “kgm-3”

4.     Line 291: “line” to “line.”

Reviewer 3 Report

Interesting paper. The conclusions at the end could be a little bit more to-the-point.

Small remark: in the figures is plotted 'the Mean seasonal SSH variations", please explain what means "mean" (average of several measurements during one month, average over several years; how many years, how many observations per month) ?

Nice to know, but not directly relevant for the conclusions: In the years 1890-1895 mr.  J.P. van der Stok published a number of papers on the tides in the Indonesian Archipelago under the title: Studiën over getijden in den Indischen Archipel. See https://kennisbank-waterbouw.nl/tresor/KIvI.php?code=M&sort=A. By clicking on the blue "1" in column 2 you can download the pdf. Unfortunately the papers are in Dutch.

Reviewer 4 Report

I have a couple of technical comments below, but fundamentally I do not see the point of this paper.  Also, without the error discussion mentioned below, the paper should not be published. 

L 85: If I understand the previous part of the sentence with this, “should” should be replaced by “needs to be”.  Also, it is unclear why some amount of along-track averaging (as opposed to “gridding”) is not investigated – actually then sort of discussed in L 101.

L 102: 90 days seems like a very long averaging time to start out with.  Certainly one should investigate other time spans.

L 105: Needs colon before, comma after interannual variations.

L 106: What exactly is the high pass filter?

Fig 2, L 139-156: Discussion of the error/uncertainty of the plotted points is needed.  In particular, seasonal errors in wet and dry tropo corrections and, if this is SSHA, tides, need to be considered.  Tides in areas <~300 m are likely to be quite uncertain.

Fig 5, 7, 9, 10: These are quite confusing.  Where did all the extra points come from?  The sizes are hard to distinguish.