the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Characterizing the surge behaviour and associated ice-dammed lake evolution of the Kyagar Glacier in the Karakoram
Guanyu Li
Duncan J. Quincey
Liam S. Taylor
Xinwu Li
Shiyong Yan
Yidan Sun
Huadong Guo
Abstract. Glacier surges are prevalent in the Karakoram and occasionally threaten local residents by inundating land and initiating mass movement events. The Kyagar Glacier is well-known for its surge history, and in particular its frequent-blocking of the downstream valley, leading to a series of high-magnitude glacial lake outburst floods (GLOFs). Although the surge dynamics of the Kyagar Glacier have been broadly described in the literature, there remains an extensive archive of remote sensing observations that have great potential for revealing specific surge characteristics and their relationship with historic lake outburst floods. In this study, we propose a new perspective on quantifying the surging process using successive Digital Elevation Models (DEMs), which could be applied to other sites where glacier surges are known to occur. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEMs, High Mountain Asia 8-meter (HMA) DEMs and the Shuttle Radar Topography Mission (SRTM) DEM were used to characterize surface elevation changes throughout the period 2000 to 2021. We also used Landsat time-series imagery to quantify glacier surface velocities and associated lake changes over the course of two surge events between 1989 and 2021. Using these data, we reconstruct the surging process of Kyagar Glacier in unprecedented detail and find a clear signal of surface uplift over the lower glacier tongue, along with uniformly increasing velocities, associated with the period of surge initiation. Seasonal variations in flow are still evident throughout the surge phase indicating the presence of water at the glacier bed. Surge activity is strongly related to the development and drainage of the terminal ice-dammed lake, which itself is controlled by the drainage system beneath the glacier terminus.
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Guanyu Li et al.
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RC1: 'Comment on tc-2022-253', Anonymous Referee #1, 07 Mar 2023
The authors provide detailed analyses of the surge cycle of Kayagar Glacier. They processed time series of glacier velocities and elevation changes and applied trend detection approaches on pixel scales to identify surge parameters like the duration, onset date, and end date.
Even though the knowledge regarding the surge cycle of Kayagar Glacier did not enhance much, the method applied to automatically detect the surge parameters seems to be promising. An application on large scales would be quite interesting.
I do have some moderate comments and suggestions for revisions though, which I would like to see addressed. Most prominently, the usage of SRTM as reference DEM for all elevation change analysis might lead to some issues; see the detailed comment (L146) below. Additionally, the filtering of the dh values needs to be adjusted to the different observation periods (L152).
Moreover, I think some of the figures could be added/improved to show more relevant information, and the discussion could be extended a bit. More detailed comments are given below.
L54: The GLOF was in 2015. Check the reference. It is from 2014.
L58: Why was the risk high? More information would be nice
L59: How did they figure it out that there were some surges before 2000?
L62: replace “surface conditions” with “parameters”
L63: replace “mass balances” with “surface elevation changes”
L78: please provide a reference for “polythermal”
L143: Which areas did you use for the coregistration? All or only off-glacier? Please clarify
*L146: Why did you compute the elevation difference relative to SRTM? SRTM is affected by SAR signal penetration. Why don’t you use a ASTER DEM from 2000 as a reference? This would reduce the bias. Moreover, SRTM has considerable voids in HMA, filled with other DEM data like ASTER GDEM2. This can lead to some biases in the elevation changes and thus in the subsequent analyses by using e.g. BEAST or PWLF. You should provide information on which areas of the SRTM DEM were filled by other elevation data.
*L152: You should apply a filter that accounts for the time difference relative to your reference DEM. e.g. for a DEM in 2010, the filter should be +/-30 m. Same for the filter for areas below 5600 m.
L214ff: It is hard to obtain the temporal evolution from the plot in Figures 5 and 6. It would be helpful if you could provide a plot of the velocity measured at the same spots as for the elevation changes (Fig. 4), or even more spots to better evaluate the temporal evolution of the velocities, in particular the monthly evolution.
L230: Any explanation why this area did not show any signal?
L242: Annual GLOF? You are talking about a single event. If not please provide more information.
L243: A graph showing the temporal evolution of the lake area (time vs. lake area) would be helpful to illustrate the variations in the lake area.
L245: what do you mean by historic? Which period?
L252: “At the beginning of the surge….” when? Please provide a date information
L254: You mention in the previous sentence that no surge front was formed. And now, you are talking about a surge front. Please clarify
L255: How did you figure out that there was compression?
L280: which profile? Unclear sentence. Please rephrase this explanation.
L302: Why does BEAST contain more information? Please explain
L307: Please introduce high abnormal change probability and add a cross-link to the respective figure
L313: You should also mention that a large amount of DEMs is needed to apply this approach. This might be a limiting factor.
Citation: https://doi.org/10.5194/tc-2022-253-RC1 -
AC1: 'Reply on RC1', Mingyang Lv, 08 Apr 2023
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2022-253/tc-2022-253-AC1-supplement.pdf
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AC1: 'Reply on RC1', Mingyang Lv, 08 Apr 2023
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RC2: 'Comment on tc-2022-253', Rakesh Bhambri, 27 Mar 2023
Summary This study presented a detailed study of surges of Kyagar Glacier and associated ice-dammed outburst burst floods using a time series of Landsat satellite imagery and ASTER digital elevation models. The manuscript is well-written and nicely structured, and I have given a few minor suggestions for improvement. In the introduction, there is a need to highlight gap areas in previous studies. L21 ‘from’ 2000 to 2001. L23 data‘sets’. L25 Seasonal variations in ‘surface‘flow. L26 Surge activity ‘of Kyagar’ L29-75 Please refer basic papers on Surge glaciers in the introduction (Jiskoot 2011; Truffer et al. 2021). L35 “The Karakoram is one such zone (Guillet et al., 2022; Sevestre and Benn, 2015).” You can merge a very small sentence with the previous or later sentence. L40 You can replace Bhambri et al. (2017) with Bhambri et al. (2019), as the previous reference is related to only the surging process. In contrast, the 2019 reference is based on GLOFs events associated with Surging glaciers. L56 over previous surge events. You can refer more references (Haemmig et al., 2014; Bhambri et al., 2019). L60 Bhambri et al. (2019) also reported a 1990s surge from 1994 to 1997 (Fig 3). You may mention it here. L66 “Kyagar Glacier is an ideal case on which to test a new approach for describing glacier surge events using DEMs generated from ASTER images”. Bhambri et al. (2019) also used time series (10 DEMs) of ASTER DEMs to understand the evolution of surge (Supplementary Fig. S6). However, your study used a large number of ASTER DEMs, and you may highlight this here. L66 “Kyagar Glacier is an ideal case on which to test a new approach for describing glacier surge events using DEMs generated from ASTER images”. You may refer here Pitte et al. (2016), possibly the first used time series of ASTER DEMs for glacier surge study. L69 the best of our knowledge, no earlier study used HMA DEMs for understanding the evolution of the Kyagar Glacier surge, and you may highlight this here. L83 You may replace Bolch et al. (2012) with Bookhagen and Burbank (2006) and Thayyen, and Gergan (2010). L93 ice crevasses and “ice pinnacles” (old 1920s field photographs show this). L148-149 “Non-glacier pixels with values greater than 3 standard deviations from the mean were discarded (Ragettli et al., 2016), and the vertical offsets of most selected ASTER/ HMA DEMs relative to SRTM over stable terrain were reduced to within ±2 m.” Non-glacier pixels and stable terrain are mentioned in this sentence. Are Non-glacier pixels not contain stable terrain pixels? Please check. L184 Landsat 7. You can shift lines 1991-192 on SLC here and link with this sentence. L204 You may replace one with the first surge and the other with the second surge. L238-239 “We investigated the evolution of the ice-dammed lake using visual interpretation of satellite images and the SRTM DEM (Fig. S1-S11).” You can shift this line in the method part. Fig 1 Some north-facing glaciers do not contribute to Kaygar glacier ice-dammed lake. Please carefully check. Fig 2 In this figure, you may mark the western and eastern branches. Fig 5 and 6. The legend of this fig may be improved, and image pair information may be present in the same line. Fig 7 You may also add non-glacier elevation change in this fig which will present the accuracy of elevation change at the non-glacier area. I hope this will help. References Bhambri, R., Hewitt, K., Kawishwar, P., Kumar, A., Verma, A., Tiwari, S. and Misra, A., 2019. Ice-dams, outburst floods, and movement heterogeneity of glaciers, Karakoram. Global and Planetary Change, 180, pp.100-116. Bookhagen, B. and Burbank, D.W., 2006. Topography, relief, and TRMM‐derived rainfall variations along the Himalaya. Geophysical Research Letters, 33(8). Jiskoot, H., 2011a. Glacier surging. In: Encyclopedia of Earth Sciences Series. Springer, Netherlands, pp. 415–428. Pitte, P., Berthier, E., Masiokas, M.H., Cabot, V., Ruiz, L., Ferri Hidalgo, L., Gargantini, H., Zalazar, L., 2016. Geometric evolution of the Horcones Inferior Glacier (Mount Aconcagua, Central Andes) during the 2002–2006 surge. J. Geophys. Res. F Earth Surf. 121, 111–127. https://doi.org/10.1002/2015JF003522 Thayyen, R.J. and Gergan, J.T., 2010. Role of glaciers in watershed hydrology: a preliminary study of a" Himalayan catchment". The Cryosphere, 4(1), pp.115-128. Truffer, M., K¨a¨ab, A., Harrison, W.D., Osipova, G.B., Nosenko, G.A., Espizua, L., Gilbert, A., Fischer, L., Huggel, C., Craw Burns, P.A., Lai, A.W., 2021. Glacier surges. In: Snow and Ice-Related Hazards, Risks, and Disasters. Elsevier, pp. 417–466. https://doi.org/10.1016/b978-0-12-817129-5.00003-2.
Citation: https://doi.org/10.5194/tc-2022-253-RC2 -
AC2: 'Reply on RC2', Mingyang Lv, 08 Apr 2023
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2022-253/tc-2022-253-AC2-supplement.pdf
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AC2: 'Reply on RC2', Mingyang Lv, 08 Apr 2023
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