the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Apr 2026
Implications of glacier detachment triggered by a surge event at Dehdal Glacier in the Pamir Mountains, using daily PlanetScope imagery
Abstract. Surge-type behavior and low-angle glacier detachments in small debris-covered mountain glaciers remain insufficiently documented. This study investigates the surge of the Dehdal Glacier in the northwestern Pamirs during 2025–2026, using daily PlanetScope satellite imagery. Multi-epoch uncrewed aerial vehicle (UAV) orthomosaics and digital elevation model (DEM) differencing from 2019 to 2023 reveal significant pre-surge internal mass redistribution, evidenced by surface thickening of the central tongue and surface lowering in both the upper glacier and the distal tongue, suggesting progressive internal destabilization. Demonstrated by PlanetScope imagery, the surge evolved through three distinct phases, which shows that surge initiation occurred internally and subsequently propagated down-glacier toward the terminus, resulting in detachments, accelerated ice flow, and reoccupation of the valley floor. Two low-angle detachments moved ice up to 4.7 km down-valley, depositing an estimated 4–5 × 106 m³ of ice on the valley floor. By January 12, 2026, the glacier had largely stabilized, with the primary glacier tongue covering approximately 1.83 km² and a detached ice mass of about 0.26 km² persisting farther downstream, resulting in a total ice area of roughly 2.09 km². Notably, the recurrence interval of 9–10 years since the previous surge is significantly shorter than the earlier 20–30-year intervals. This shortened interval is unlikely to be due to seismic activity or to complete reservoir regeneration, and it occurred during warmer, drier conditions than the 1981–2010 baseline, which increased by +1.11 °C. These findings provide new insights into glacier flow instabilities in High Mountain Asia and highlight the geomorphic impacts of small glacier dynamics under increasing climatic stress.
- Preprint
(3361 KB) - Metadata XML
-
Supplement
(550 KB) - BibTeX
- EndNote
Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-1923', Anonymous Referee #1, 05 Jul 2026
-
RC2: 'Reviewer comment on egusphere-2026-1923', Anonymous Referee #2, 08 Jul 2026
This is generally a very well written manuscript, that documents a very detailed dataset and an interesting glaciological event. The data alone is of interest to the community, and the case (somewhere between a surge and a detachment) demonstrates novel and interesting behaviour.
My major caveat is that the manuscript itself seems to present the event studied as either a weird surge that led to detachment, or a strange small detachment. Much more clarity is needed from the start of the manuscript on this. The event itself seems to be outside of the usual surge cycle, so I wasn't convinced that the event wasn't just a detachment rather than a surge triggered detachment - more evidence on this is needed as to why this interpretation was favoured. It would be better if the abstract itself and introduction framed this dichotomy between surges and detachments a bit more clearly.
I also thought that more reference should be paid to the enthalpy based surge model. Does this glacier suddenly exceed an enthalpy threshold triggering the event? What led to this?
It is hard to make specific recommendations on this, other than to rewrite the manuscript with more clarity that they are proposing a new "hybrid" surge-detachment (though I wasn't clear in the end if this was the case).
Citation: https://doi.org/10.5194/egusphere-2026-1923-RC2
Data sets
Derived datasets for the 2025–2026 surge of Dehdal Glacier (Pamir Mountains, Tajikistan) Mustafo Safarov https://doi.org/10.5281/zenodo.19052838
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 281 | 189 | 21 | 491 | 36 | 17 | 16 |
- HTML: 281
- PDF: 189
- XML: 21
- Total: 491
- Supplement: 36
- BibTeX: 17
- EndNote: 16
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
The manuscript addresses several challenging and interconnected aspects of glacier dynamics, including glacier ‘geometry’ (which I think they should really discuss as hypsometry), surge-type behaviour, debris-covered glaciers, and their potential relationship with contemporary climatic conditions. These topics remain among the more difficult areas of glaciological research because they involve complex interactions and untangling the relative importance of these processes is inherently difficult, making detailed observational studies such as this particularly valuable.
Overall, I found the manuscript to be very well written and scientifically rigorous. The observational dataset is impressive, and the methods are described in sufficient detail to ensure that the study is reproducible. There is a particularly comprehensive description of the remote sensing workflow, velocity estimation, DEM differencing, and uncertainty assessment. Although I cannot provide detailed comments on some of these, I feel that the methodological transparency will be valuable for future investigations of similar surge and detachment events.
One of the major strengths of the study is its focus on the pre-surge evolution of the glacier.. Here, the authors provide observations of glacier evolution during the years preceding the surge, documenting progressive surface elevation changes and dynamic reorganisation before the onset of rapid motion. These observations represent an important contribution towards understanding the preparation phase of surge-type glaciers.
The paper also provides an detailed reconstruction of the 2025–2026 event itself. The combination of daily PlanetScope imagery with UAV observations allows the authors to document the sequence of glacier acceleration, detachment, and subsequent stabilization at a temporal resolution that has rarely been achieved for surge-type glaciers. This high-frequency observational record will likely become an important reference dataset for future studies of glacier surges and low-angle glacier detachments.
General comments
Introduction would benefit from a few lines discussing that surge-type glaciers tend to be geographically located in clusters that require a certain a precipitation/temperature relationship.
In the ‘study area’ section (lines 98-104). It may be helpful to include something about the average length of surge-cycles in your region compared to locations globally.
Some of the figures are not that clear to see what the authors are describing. For example Fig6. I realise they have drawn polygons around areas but actually visually these ‘detachments’ are not that recognisable for the reader with no prior knowledge of this location. Since the Panet imagery is c.3 m resolution it would be better to have some zoomed in images to confirm what the authors are describing. As it stands panel ‘c’ is not clear an meaningless.
Can you better quantify the reservoir zone evolution from your datasets? I think this is partially done in Figure 3 but could be more effectively used to state the volume gained, lost, %of the glacier involved. This can help to assess if the glacier was approaching some instability threshold?
I am wondering, given the detailed datasets generated, is it possible to make a stronger distinction between surge and the detachments? Can you estimate the driving stress before failure, show whether the detachment occurred along a pre-existing shear zone or establish the longitudinal strain rate before detachment? This all may help your interpretations.
Specific comments
L: 41-45 I would include the Lovell citation in the first paragraph because you are talking about hazards, so that paper is most relevant.
L: 70-80 Some of this is repetitive of prior paragraphs. Just double check if this can be consolidated.
L 95 Can you state what ‘historical records’? This can be really useful to those reconstructing paleo-surges from the pre-instrumental record.
Figure 1: In ‘b’ I would move the north arrow to above the scale bar. Or move the scale bar and north arrow to the top left
L 105-109 I am not sure how this adds to your section. It seems a bit repetitive….It may be better to say something specific about the settlements and local infrastructure?
L135-137 I may be confused but why did you extract the elevation profile from Google Earth Pro? Yes, you can get a profile from GE but what are the error margins associated with it? Could you have used another dataset?
L460 This type of activation pattern is also seen in Svalbard – so you can say that it occurs in other surge-type glacier locations.
L487 have you mentioned somewhere approximately how much debris is covering the surface of Dehdal? If not, I would include it.
L565 when you say ‘geometry’ I think it would be better to consider your discussion in terms of glacier hypsometry.
L590 This may be a comment to consider earlier in the paper – but from the images it looks like you have two contrasting lithologies? So is the whole area underlain by fine grained sediments?