the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Linking Glacier Retreat with Climate Change on the Tibetan Plateau through Satellite Remote Sensing
Abstract. Under global climate change, glaciers on the Tibetan Plateau are experiencing severe retreat, which significantly impacts the regional water cycle and the occurrence of natural hazards. However, detailed insights into the spatial-temporal patterns of this retreat and its climatic drivers remain insufficiently explored. In this study, an Adaptive Glacier Extraction Index (AGEI) is proposed based on analysis of multispectral Landsat images integrated with the Google Earth Engine, and comprehensive and high-resolution mapping of glaciers on the Tibetan Plateau is realized at five-year intervals from 1988 to 2022; subsequently, the ERA5-Land air temperature and precipitation data are downscaled to a finer 1-km resolution; finally, impacts of the annual and seasonal change of downscaled meteorological factors on the glacier retreat are quantified. Results demonstrated a rapid yet heterogeneous pattern of glacier retreat across the Tibetan Plateau between 1988 and 2022, with retreat rates ranging from 0.14 ± 0.07 % to 0.51 ± 0.09 % annually. A notable trend was observed where most glacier areas experienced a decrease from 1990 to 2000, followed by a slight increase. From 2010, a majority of the glaciers exhibited either a static state or minimal retreat. The most pronounced impact of annual temperature on glacier retreat is observed in Zone VIII, with a value of -9.34 × 103 km2/°C, and the most restraining impact of precipitation on glacier retreat reaches 261 km2/m, which is observed in Zone VI for the spring season. Further, it identifies the influence of debris thickness on the glacier retreat rate. These insights are pivotal in comprehending the temporal and spatial heterogeneity of glacier retreats, and in understanding the effects of climatic variations on the state of glaciers on the Tibetan Plateau.
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Status: open (until 23 Aug 2024)
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RC1: 'Comment on egusphere-2024-1083', Connor Shiggins, 02 Jul 2024
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The manuscript presented by Zhao and co-authors put forward a glacier mapping tool using Landsat collections and reanalysis data over the Tibetan Plateau (TP).
The manuscript is generally well written and mostly well structured, however I have made some suggestions to try and improve the flow of the manuscript.
My main and minor comments can be found below:
Main:
- Why is RGI 6.0 being used instead of RGI 7.0 which was published in September 2023? I appreciate if analysis had been carried out before the most recent release, however I think it is important the most up to date data products are used in current day studies as I know there can be large differences in glacier extents between version 6.0 and 7.0 and therefore may impact your results significantly. I will leave this to the decision of the handling editor, but I would suggest using RGI 7.0 to ensure at the time of publication, the results reflect the most current version.
- There is no consideration of the poor ‘completeness’ value in Table 2, particularly for 2010. The F-1 scores for glacier mapping are moderate, I would not consider them strong metrics in support of the method. It is of course fine to have these scores, however, there needs to be consideration of why the scores are this low and how this may impact the results in the discussion.
- Each section of the paper (i.e. results, discussion) does not need to have an introductory section of how it is structured and I would suggest deleting them and going straight into the text of the section.
Minor:
- L17: Would just note what time period this 'slight increase' was
- L19: Would consider stating geographically where these 'zones' are as out of context as they don't mean very much as no lead in from the abstract (i.e. NE of TP)
- L35: I get what you mean, but I would rephrase the opening on this paragraph saying 'Glacier change can be measured using variations in...' to be clearer
- L42: Would put the reference for each method after it was referred to i.e., spectral analysis (ref), object-based (ref), etc.
- L46: needs a reference for debris-free glaciers before full stop
- L51: are 'quality' and 'resolution' not the same thing? Also, what type of resolution, spatial or temporal? If both I would suggest stating the limitation of spatio-temporal resolution over the TP.
- L58: Climate change seems a bit broad here, is it the increasing air temperature? Would clarify
- L77: If you state 'numerous studies' I would suggest citing a handful of them as examples
- L82-85: not convinced this is required for such a specific structure, think you're fine with just the aims of the paper being highlighted
- L86: Just call it Study Area
- L117: Would call it data and methods instead of materials
- L118: This text is not needed - would go straight to 3.1
- L124: I would just be careful saying images via GEE catalog are 'open-access' - while they are for individuals, there is commercial cost to access the platform
- L124: Would merge these sentences, suggest at start of sentence saying Landsat data is used via GEE
- L158: Figure 2 caption - Is this the total number of Landsat images or the total number used in the study with less than 60% cloud as defined by your study? Would clarify
- L162-164: basically, the same as previous, would suggest merging and stating previous studies chose 0.4 as a threshold and therefore it was chosen here
- L167-169: same applies about thresholding values NDWI, just merge them and say you chose 0.4
- L171: 'Therefore' does not fit here as does not follow the previous sentence
- L173-174: the final paragraph is just repetition of values you've defined - suggest deleting
- L183: What holes? What do you mean 'filled'? Interpolated? Would clarify
- L185: sentence does not make sense - what do you mean 'validated using reference debris-free glaciers'?
- L253: Can Fig 3 be made bigger?
- L255-258: Delete introductory
- L275: Figure 4. Would suggest having the map as a) at the top of the figure then having panels b-i stacked. The lettering order seems a little confusing
- L287: What do you mean the glaciers mapped between 2000 and 2005 'exhibit greater consistency'?
- L300: Table 2 metric scores – see main comment 2
- L400: I think Fig.10 and above text is more results than discussion. Would suggest moving to results. Do you have any numbers for the total area difference between the two methods? Would add to the argument of the AGEI method
- L405: Would refrain from starting discussion sentences 'Fig X', if wanting to directly refer to the figure, place in brackets at the end of the sentence
Citation: https://doi.org/10.5194/egusphere-2024-1083-RC1
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