the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
31 May 2021
31 May 2021
Recent contrasting behaviour of mountain glaciers across the European High Arctic revealed by ArcticDEM data
- Cryosphere Research Group, Adam Mickiewicz University, Poznań, Poland
- Cryosphere Research Group, Adam Mickiewicz University, Poznań, Poland
Abstract. Small land-terminating mountain glaciers are a widespread and important element of Arctic ecosystems, influencing local hydrology, microclimate, and ecology, among others. Due to little ice volumes, this class of ice masses is very sensitive to climate warming, the latter of which is extremely well manifested in the European sector of the Arctic, i.e. in the Barents Sea area. Archipelagos surrounding the Barents Sea, i.e. Svalbard (SV), Novaya Zemlya (NZ), and Franz Josef Land (FJ), host numerous populations of mountain glaciers, but their response to recent strong warming remains understudied in most locations. This paper aims to obtain a snapshot of their state by utilizing high-resolution elevation data (ArcticDEM) to investigate the recent (ca. 2011–2017) elevation and volume changes of 382 small glaciers across SV, NZ, and FJ. The study concludes that many mountain glacier sites across the Barents Sea have been in a critical imbalance with the recent climate and might melt away within the coming several decades. However, deviations from the general trend exist, e.g. a cluster of small glaciers in north SV experiencing thickening. The findings reveal that near-stagnant glaciers might exhibit contrasting behaviours (fast thinning vs. thickening) over relatively short distances, being a challenge for climate models, but also an opportunity to test their reliability.
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Jakub Małecki
Status: final response (author comments only)
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RC1: 'Comment on tc-2021-165', Anonymous Referee #1, 04 Jul 2021
Please find the reviewer's comments in attachment.
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AC1: 'Reply on RC1', Jakub Małecki, 14 Nov 2021
Dear Reviewer,
Thank you very much for constructive criticism, your comments are much appreciated and will certainly improve the quality of the manuscript. I read all your questions and suggestions with great interest. Regarding your general comments, please let me respond below.
Comment #1 - about the impact of spatial coverage (limited to only 23% for one of the sites) on the reliability of the results
The uncertainties estimated for overall glacier elevation change rates for different sites, dh/dt, range from 0.04 to 0.19 m/y. However, these values might be much higher for individual elevation bins. This commonly results from the small size of elevation bins, which automatically increases the uncertainty, further boosted to metre-scale values at low data coverage. However, large uncertainties typically refer to only a few bins with very low proportion of the overall glacier area at a given site. For this reason, these do not have a large impact on the overall dh/dt uncertainty.
In order to show how reliable the estimates of dh/dt are, a sensitivity test suggested by the Reviewer will be applied to the final version of the manuscript.
Comment #2 - questioning whether glaciers studied in the paper (accounting to ca. 20% of the whole population of mountain glaciers of the three study regions SV, NZ and FJ) are representative of the whole population
The map of sites studied in the manuscript evolved from less than 20 sites at earlier stages of work, up to 29 in the version submitted for the review. New sites were progressively added to the analysis to 'catch' the gradients described in the manuscript and this process was eventually finished when sufficient level of detail was achieved. Moreover, I think I could not add much more sites due to the limited availability of useful ArcticDEM data from summer seasons and to a lack of larger clusters of mountain glaciers over large areas of SV, NZ and FJ.
More importantly, I do consider the sites presented in the manuscript as representative of the wider population of mountain glaciers in the Barents Sea sector. One argument is that the study sites cover the regions rather uniformly and represent different glacier settings. The stronger argument is, in my opinion, that glacier elevation changes are relatively homogenous between sites within larger subregions (see e.g. Figure 4). This suggests that a denser array of study sites would not necessarily bring much new information, however, smaller anomalous sites might still remain undetected with the presented data.
Therefore, the revised version of the manuscript will make more use of the wonderful dataset by Hugonnet et al. (2021), where one might compare dh/dt of glaciers studied in this manuscript against the overall population of mountain glaciers. This might also answer some of the specific comments by the Reviewer.
Comment #3 - about missing references from the most recent literature, including the mass balance model for SV by van Pelt et al. (2019)
I agree, this will be corrected in the revised version of the manuscript. The excellent work by van Pelt et al. (2019)(or "vP19") was omitted by a mistake and this will be corrected. However, interpretation of the mountain glacier changes observed in my analyses in the background of vP19 outcomes would require caution. Note that vP19 calculates generally positive long-term balances in many areas dominated by mountain glaciers in SV, e.g. central Nordenskiold Land, Bunsow Land and Nathorst Land, being in contrast with their retreat over the past decades. This is quite common for regional mass balance models and that is why I personally consider regional simulations the best for giving an overall picture, rather than for providing adequate reproduction of details, such as the mass balance of small mountain glaciers.
Again, please let me thank you for your time and effort.
Kind regards,
Jakub Małecki
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AC1: 'Reply on RC1', Jakub Małecki, 14 Nov 2021
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RC2: 'Comment on tc-2021-165', Anonymous Referee #2, 16 Oct 2021
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2021-165/tc-2021-165-RC2-supplement.pdf
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AC2: 'Reply on RC2', Jakub Małecki, 14 Nov 2021
Dear Reviewer,
Thank you for your time and work on my manuscript and all suggestions you made to improve its quality. There is a number of issues raised in your review, please may I respond to the most important ones below.
Comment #1 – the presented manuscript discusses only selected mountain glacier sites, while the recent study by Hugonnet et al. presents elevation changes of almost every glacier in the world.
It is hard to argue that the study by Hugonnet et al. (2021)(or "H21") is a game changer and a landmark dataset in glaciology. No study with incomplete data coverage can compete with H21 and, obviously, this has not been the aim of my manuscript. From the very beginning it was meant to make use of test-sites, rather than trying to achieve full data coverage. Simply speaking, there was not enough ArcticDEM data that was useful for my analyses, because in many subregions of SV, NZ and FJ there is only a handful of DEM strips to browse from and even less from summer seasons.
However, even though only part of mountain glaciers in SV, NZ and FJ are studied in the manuscript, I do consider the sites as representative of the wider population of mountain glaciers in the Barents Sea sector. One argument is that the study sites cover the regions rather uniformly and represent different glacier settings. The stronger argument is, in my opinion, that glacier elevation changes are relatively homogenous between sites within larger subregions (see e.g. Figure 4). This suggests that a denser array of study sites would not necessarily bring much new information, however, smaller anomalous sites might still remain undetected with the presented data.
After careful reading of the two reviews I now see the need for a more extensive discussion and comparison between my dataset and the one by H21. The latter might serve as a benchmark, e.g. to show whether the study sites selected for analysis are representative for the general population of mountain glaciers in SV, NZ and FJ. Such an attempt will be presented in the revised version of the manuscript.
Comment #2 – glacier surges, common in SV and NZ, are not discussed in the manuscript
Obviously, this will be corrected. However, as far as I know, no glacier studied in the manuscript has surged within the past decades, so this dynamic instability likely does not play a significant role in geometry changes of the study glaciers.
Comment #3 – outcomes of mass balance models, e.g. van Pelt et al. (2019) and Noel et al. (2020) would be useful to give an insight into the processes behind the observed glacier changes
I agree, this will be elaborated in the revised version of the manuscript. The excellent work by van Pelt et al. (2019)(or "vP19") was omitted by a mistake and this will be corrected. However, interpretation of the mountain glacier changes observed in my analyses in the background of vP19 outcomes would require caution. Note that vP19 calculates generally positive long-term balances in many areas dominated by mountain glaciers in SV, e.g. central Nordenskiold Land, Bunsow Land and Nathorst Land, being in contrast with their rapid retreat over the past decades. This is quite common for regional mass balance models and that is why I personally consider regional simulations the best for giving an overall picture, rather than for providing adequate reproduction of details, such as the mass balance of small mountain glaciers.
...
In the end, your work, including linguistic corrections, is greatly appreciated.
Kind regards,
Jakub Małecki
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AC2: 'Reply on RC2', Jakub Małecki, 14 Nov 2021
Jakub Małecki
Jakub Małecki
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