Summary
I have reviewed the manuscript “Long-range terrestrial laser scanning measurements of summer and annual mass balances for Urumqi Glacier No. 1, eastern Tien Shan, China” submitted to The Cryosphere by Xu et al. The article describes using terrestrial laser scanning to look at annual and intra-annual mass balance for Urumqi Glacier No. 1 over a two-year period, and compares the geodetic results with the glaciological mass balance.
The article presents some interesting results, but there is not much new material compared with the articles from 2017 and 2018. It is not clear (apart for the obvious reasons) why the authors are publishing these results in several papers. It is suggested that further analysis is done of the results by incorporating velocity measurements, and going into more detail of the thickening or balance at higher elevations, and thinning at lower elevations .
Generally, the article is difficult to read for several reasons. The English needs to be considerably improved, there is an overabundance of acronyms and the order in which topics are dealt with is not always logical.
Acronyms should be avoided where possible. E.g. ICP is used only twice, so should be written out. Write out what the acronym means on first use, even for terms such as “w.e.”. DMS should be replaced by “the meteorological station” or “the met. station”. Use of this acronym every time the met station is referred to is confusing.
Comments on the text and grammar
p. 1, line15-16. Change to “…. well-suited for repeated glacier mapping, and thus determination of annual and seasonal geodetic mass balance.”
line 18. Change to “for two consecutive mass balance years …….”
Line 24. Change “satisfying” to “satisfactory”
Line 28. Change “function known as” to “concept of”
Line 34. Change “Ongoing” to “Continuous”
p.2 line 9. The geodetic method doesn’t “measure” all mass balance processes as such. Change the sentence to “The method includes all processes that affect the surface ……….”
Line 15. Change “burgeoning” to “emerging”
Line 17. Change to “to calculate geodetic mass balance and changes in glacier volume …”
Lines 17-19. It is unnecessary to have to many references. Several of these had no new techniques, merely applying the same technique to different areas. Also, add the first studies of intra-annual changes in mass balance from laser scanning,
Pellikka, P. and W.G. Rees, eds. 2010. Remote sensing of glaciers: techniques for topographic, spatial, and thematic mapping of glaciers. Boca Raton, FL, CRC Press/Taylor & Francis. 330pp. ISBN-10: 0-415401-66-6, ISBN-13: 978-0- 415-40166-1 (or Vetter et al, 2009 article) and
Geist et al (2005), Investigations on Intra-annual elevation changes using multi-temporal airborne laser scanning data: Case study Engabreen, Norway.
Line 19. Replace “advantageous” with “effective”. Replace “wide” with “extensive”.
Lines 19-21 require more explanation – “what is meant by “the difficulty of studying small-scale processes”? Small-scale processes are not the focus here. In addition, why is the presence of rock outcrops a problem for airborne observations, rather than ground-based? Usually the opposite would be assumed.
Line 22. Change “evolutions of” to “changes in”.
Line 23. Delete “reference glaciers in particular”, as this is irrelevant. Change “-resolution” to “high.resolution”.
Lines 25-26. From “Being” change to “The scanner is a Laser Class 3B, with laser wavelength in the near-infrared (~1064 nm), and thus well.suited for measuring snow- and ice-covered terrain in…..”
Line 27. “Some recent studies” – is it some or one? The reference is to Gabbud et al, 2015, which describes a study on one glacier.
Lines 28-32. From “however”, change to “however, only the middle and lower elevations were measured as the glacier is relatively big. Another study reports the performance of the Riegl VZ® -6000 in monitoring 30 the mass balance of five glaciers in the European Alps; the surface terrain of each glacier can be almost entirely detected using one scan position since these glaciers are very small and have steep terrain (Fischer et al., 2016). For medium-sized and large glaciers with flat terrain, however, a single scan position cannot capture the whole glacier surface.”
Line 35. Delete “-term”
Line 36. Delete “Riegl VZ® 6000”
p.3. Line 1. Break the sentence up, e.g. full-stop after results, and start the next sentence “An accurate ….”
Line 2. Change “received attention” to “been performed”
Line 3. Was the study done at a monthly scale, or were two measurements made one month apart to get net mass balance over one month? This needs to be clearer.
Lines 6-7. “besides we only considered snow/firn densities in the geodetic mass balance calculations” etc. – this sentence doesn’t make sense.
Line 8. Change “mass balance” to “mass changes”.
Line 9. What is meant by “Meteorological influences on the elevation changes” from Huss (2013)? Is this referring to changing mass balance gradients?
Generally, this whole paragraph down to line 24 on page 3 needs to be rewritten.
Bader (1954) is referenced later in the text, but could be introduced here, in lines 13-14.
Line 17. Change “consecutive years” to “consecutive mass balance years”.
Line 30. Why “accelerated” recessions? Do you mean just recessions?
Line 30. Delete “was” – this was a natural occurrence.
Line 31. Why “enhanced”? Do you mean “increased”? If increased, over which period?
p. 4, line 3. Change “accumulation rate is quicker” to “accumulation is higher”.
Line 17. Change “-precision” to “high-precision”.
Lines 24-25. Change to “point. The four scan positions were surveyed using real-time kinematic ……..”
Line 26. Change “facilitate” to “give”.
Line 27. Change “RTK surveys” to “survey”.
Line 32. Delete “As to UG1”
Line 35 to p. 5 line 1 Change “no less than” to “at least”
p. 5. Line 19. “advantageous” – compared with what?
p. 6, line 20. Changes “researches” to “researchers”
Line 22. State Sorge’s Law, rather than just referencing Bader (1954).
p. 7, line 1. Delete “3-D”
Line 4 – insert «descriptive» in front of «free water content». This is in the original article, otherwise you are suggesting that free water content can be calculated merely by digging a snowpit.
Line 10. Change to “………….observed using stakes and snow pits, since 1959 ……..”
Line 15. Change “where snow has accumulated” to “in the accumulation area”.
Line 27. After respectively, insert “and the different between these two, i.e.”
p. 8, line 4. “probably led to an overestimate of the glacier extent” – when?
Line 11. Change “assessments” to “assessment”.
Line 20. Why “finish”? replace with “perform”?
Line 22. Change “stabilized” to “established”.
p. 9, line 1. “quantitatively”. Should this be “qualitatively”? Othewise the sentence doesn’t make sense.
Lines 5-6 – This sentence regarding the supraglacial river doesn’t make sense and needs to be rewritten.
Line 34. Change beginning of this paragraph to “There are additional sources of error for …….”
P. 10, line 11. Change “glaciers” to “glacier”.
Lines 11-12 – the figures given here from Andreassen et al (2016) differ from the values given in the article.
Line 34. Why “remarkable”? What is remarkable about it? Or do you mean significant?
p. 12. Line 6. Replace “satisfying” by “satisfactory”.
Line 8. Replace “know” by “give”
Line 10. Change “at the steep elevations” to “on steep slopes”.
Lines 13 - 15. These two sentences need to be further clarified. Where are the annual vertical ice velocities reported? The geodetic results were more positive in lower-elevation regions – does this not contradict results for the Western Branch given on page 11?
Line 20. As this is before section 6.3, a short explanation should be given here.
Line 30. What are alcove terrains?
Lines 36-37. Change to “Note that we did not get better results with more scan positions since this would probably decrease the quality of the MSA”.
Section 5.1 is confusing – rewrite this to say something about the general pattern, then the specifics for the different years.
The pattern of thinning in lower parts of a glacier and thickening in the upper parts has been observed on many other glaciers. (e.g. Moholdt et al (2010) Recent elevation changes of Svalbard glaciers derived from ICESat laser altimetry.). This pattern can be discussed with reference to Urumqi 1.
Section 5.2. This needs more explanation for why annual density conversions higher than summer. The converse would be expected.
Line 13. Change to “covered by a thin snow layer at the end ……..”
P. 13, line 2. Change “locate” to “be located”
Line 28. Change “glaciers” to “studies”
P. 14, Lines 1-18. It would make more sense to move the discussion of internal accumulation to where internal ablation is discussed. It is confusing to state that UG1 is a cold glacier, then to jump straight into internal ablation.
Equation 11. Why is the interval between the ELA and the terminus only considered?
Line 10. Other sources of internal ablation should be discussed.
Lines 16-18. How applicable is the 4% value given by Zemp to Urumqi Glacier No. 1?
Line 23. Delete “simiultaneously”.
Lines 24-25. What is meant by “observed discrepanices” and “had not been statistically identified”? this paragraph is confusing and needs more/better expalanation.
Line 30. “On the eve” – does this mean the day before or in the evening? Please clarify.
Line 30. Change “latest” to “last”.
P. 15. Lines 5-6. Why is the past tense used here? Change to present tense.
Lines 19-20. How can the location of stakes be identified in this way? This part is unclear.
Lines 23-24. An example of daily or sub-daily ablation would have been interesting if this was done at all during the study.
P. 16 – Most of the first paragraph is unnecessary and this can be shortened considerably. The extensive list of glacier names (lines 12-13) is not necessary.
Line 7. It is meaningless to give the area threshold to three decimal places.
Extensive rewriting is required to improve the grammar, and I have raised only the main points above.
References. There are several errors in the references, and these should be thoroughly checked.
p.18 e.g. In Abermann et al (2010) change “dems” to “DEMs” as in the original.
Cuffey and Paterson, 2010 - use the full citation for
Huang, 1999. Correct “year’s” to “years”
p. 19 Check spelling for names with diacritics, e.g. Pléiades, Radićetc.
p. 20 Use capital letters for proper nouns as used in the original articles, e.g. Rolleston Glacier, Hintereisferner
p. 21 Correct the use of random hyphens that have crept into words, e.g. in Pfeffer et al, 2014 - Kienholz, Randolph, globally
Pieczonka and Bolch (2015) should start on a new line.
Xu et al (2018) is referred to on page 2, but missing from the reference list (unless this reference should have been to Xu et al (2017).
Figures
Figure 1 – Positions of stakes and density pits are difficult to see and should be made clearer.
Figure 2 – this figure and reference in text are unnecessary, a reference to Litchi et al (2005) is sufficient.
Figure 3 – The glacier boundaries for different years needs to be clearer. Very hard to see the difference now. The (b) and (c) on the figures is hard to read.
Figure 4 – The green polygons are very hard to see. In caption, change “(the unit is m)” to “(in m)”
Figure 6 – The caption refers to black lines where are these? Also, these are meant to be the same as the corresponding boundary of figure 3, but this figure shows several glacier boundaries. ”artefact” is not the correct terminology, as it refers to something that is the result of the measurement technique or experiment, not merely missing data. “Areas” would be a better term than artefacts.
Figure 8 – Elevations in left-hand column are difficult to read – need to use a bigger font. The text in the middle and right-hand columns is also difficult to read and needs to be bigger.
Figure 9 – change “temperature” to “air temperature”
Figure 11 – this map is unnecessary, as all it shows is spatial distribution of glaciers with suitable area and slope. If for some reason this figure is retained, change area cut-off to 1.5 km2; meaningless to use 1.555 km2.
Table 2. Change “are calculated based on the elevation changes over stable terrain” to “are measures of error derived by calculating elevation changes from TLS over stable terrain (off-glacier)”. In the header columns give the terms not symbols, e.g. Error or StdDev, number of points, mean (stable terrain) and standard error (stable terrain). Give the periods in the caption rather than under the table. |
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