This is a clearly written paper which explains the somewhat unusual situation of increasing large outburst floods occurring from an ice-dammed lake in Alaska during a period of rapid glacier thinning and retreat. There have been few other studies which have described this unique situation before, and this one was a pleasure to read as it well supported by a variety of comprehensive remote sensing datasets and analyses, and a number of useful figures. I believe that it is worthy of publication, and will add to the growing knowledge of glacier lake outburst floods.

My comments are generally very minor, with the exception being the question of whether the lake outburst volume has decreased (perhaps even rapidly?) after 2015. As described in my comments for L425 below, this is a major current limitation with the study as the other datasets for lake area and lake level extend to 2023 (see Fig. 2). If the lake volume estimates could be extended to 2023, and found to be decreasing, then this would change one of the main thrusts of the paper, and perhaps even require the title to be changed from ‘larger lake outbursts’. I encourage the authors to investigate whether other DEM datasets are available that could be used to resolve this question.

Individual Comments

L23: change to: ‘to up to ~700…'

L39: I thought that we only had two ice sheets, unless you’re calling East and West Antarctica separate ice sheets? Hugonnet et al. (2021) (as well as most other studies) only refer to two ice sheets, the Greenland Ice Sheet and Antarctic Ice Sheet, so I suggest that you specify two here.

L75: change ‘storing’ to ‘storage’

L89: you state that Alaska has 667 glacier lakes, but this is incorrect: as stated in the title of Rick et al. (2022), this total is for Alaska and NW Canada. A pet peeve of mine is that studies such as yours seem to implicitly assume that Canada is part of Alaska, when clearly this isn’t true! Throughout your paper you need to ensure that you properly define which area Alaska refers to, and include Canada when necessary.

L95: figures should be referenced in sequence: you’re referencing Fig. 6 here, but haven’t even referenced Fig. 1 yet.

L165: change ‘which assume’ to ‘which are assumed’

L176: missing a bracket after 𝜌

L178: need to enter symbol for area between the brackets

L180: symbol and bracket missing at start of line

L192: presumably there is also an uncertainty from the change in surface elevation between the acquisition date of the 2019 ArcticDEM and the June 2023 radar survey? Your results suggest that this can amount to several metres per year.

L335: -2.9 requires a unit (presumably m)

L356 (& L409): some references that are missing here and describe opposite patterns (lake drainage volumes increasing over time) are Kochtitzky et al. (2020) and Painter et al. (2024), who describe how releases from ice-dammed Dań Zhùr (Donjek) Lake, Yukon, have been increasing towards present day, primarily as a result of a larger basin becoming available for the lake to form in as the glacier retreats. These damming events and subsequent releases are primarily controlled by glacier surging, but share some similarities to what is being described in this study and so it seems that they should be mentioned:

Kochtitzky, W., Copland, L., Painter, M. and Dow, C. 2020. Draining and filling of ice dammed lakes at the terminus of surge-type Dań Zhùr (Donjek) Glacier, Yukon, Canada. Canadian Journal of Earth Sciences, 57, 1337-1348

Painter, M., Copland, L., Dow, C., Kochtitzky, W. and Medrzycka, D. 2024. Patterns and mechanisms of repeat drainages of glacier-dammed Dań Zhùr (Donjek) Lake, Yukon. Arctic Science, 10(3), 583-595. https://doi.org/10.1139/as-2023-0001

L425: This is a key point that needs to be better investigated. One of the main contentions of this study is that drainage volumes from Desolation Lake have been increasing over time, but no outburst volume estimates are provided after 2015 (Fig. 2b), during a multi-year period when the level of Desolation Lake is rapidly dropping (Fig. 2c). This lack of recent volume estimates seems to be due to the lowest lake level being 197 m in an ArcticDEM from 2020-09-11. My expectation is that the lake volume dropped after 2015, which if quantified would add significantly to the story being presented, and perhaps change some of the final conclusions. The solution to providing outburst volumes after 2015 would be to use a base DEM collected when the lake is at a lower level than 197 m. I’m unsure how much searching the authors have done for datasets beyond the ArcticDEM, but there are several potential sources of DEM information for this period that address this issue:

• The USGS collected LIDAR data over at least part of the lake in summer 2019, which can be downloaded from: https://portal.opentopography.org/usgsDataset?dsid=AK_GlacierBay_B3_2019
• DEMs can be generated for free from stereo ASTER imagery, acquired regularly up to present day: https://lpdaac.usgs.gov/products/ast14demv003/
• Cryosat data has been collected since 2010, and standardized datasets are now available such as CryoTEMPO Inland Water which might provide useful elevation data: http://cryosat.mssl.ucl.ac.uk/tempo/index.html
• IceSAT2 has been operating since 2018, with elevation data from tracks over the lake available to download from locations such as: https://openaltimetry.earthdatacloud.nasa.gov/data/icesat2/

L446: dam flotation and subsequent channel enlargement has also been invoked as the casual mechanism for floods from Donjek Glacier by Painter et al. (2024)

Fig. S8: this graph is noisy, presumably because you included all available image-pair velocities no matter their separation time? You should be able to reduce this noise by removing image pairs with short and long similar separation times. For example, I used the ITS_LIVE widget tool (https://itslive-dashboard.labs.nsidc.org/) to only plot data with separation intervals of 30-300 days for your location, which produced a cleaner signal than yours.

The authors present a detailed overview of glacial lake outbursts from Desolation Lake (Alaska) using an interesting mix of methods and data. I have a few suggestions for minor adjustments but overall this reads very well, the contents are compelling and I look forward to seeing this published in TC. 

I share RC1’s view that it would be beneficial to extend the time series of outburst volume beyond 2016 if possible. If the data situation does not allow for this it would be informative to state that somewhere in the manuscript and note why DEM data sources other than the Arctic DEMs were not used. In this case the discussion should be adjusted to more clearly indicate the limitations of the data set (and its interpretation) for recent years.

Line by line comments: 

L36-39: I would suggest “glacier mass loss” instead of “glacier thinning” as a more general term but this is just semantics. I stumbled over “three ice sheets” - don’t we usually count two? 

L112 We reconstructed the outburst chronology of Desolation Lake and Lituya Glacier between 1882 and 1969 from historic air photos taken by Austin Post and from historic maps (see Supplementary Table S1). From satellite images acquired between 1972 and 2023….

Can you comment on whether you think you have missed outbursts? How comprehensive is the time series? I understand you can’t know if the data isn’t there but consider adding a short note on this, mentioning, e.g., changes in temporal coverage with new satellite missions, cloud cover issues (I assume clouds are a major limiting factor?), etc. 

L173 Lituya Glacier elevation changes were calculated within the reference glacier outline on 2013-11-08 with an area of 10.6 km2 , covering the part of the ablation zone of the glacier that dams Desolation Lake, in the following referred to as Lituya Glacier dam. This outline was cropped above the ice divide to ensure equal coverage of the elevation data (Fig 4)

I suggest moving this sentence to the beginning of the section to clarify that you computed elevation change only for the lower part (Lituya Glacier dam) rather than the entire glacier. This is important to know for the error estimation and assumptions re. density conversion and it was initially not clear to me. Also: What do you mean by “reference glacier outline”? Did I miss this? Why is that particular outline considered the reference? 

Figure 1: The authors have done a good job of presenting their wealth of data in a concise way so I think there is room to consider adding another figure. Splitting Fig. 1 into two figures would allow readers unfamiliar with the site (like myself) to have a very simple overview map at the start of the study site description. Fig. 1 currently is quite crowded and contains a lot of information. I found myself going back to Fig. 1 multiple times while reading looking for features like the ice divide mentioned later on. These things eventually become clear but I feel that the current panel a in Fig 1 (oblique photo) next to a simple, north oriented, birds-eye map and the inset showing the location in Alaska would be helpful. The other panels (historical maps and satellite imagery) are also valuable but in my opinion could be in a separate figure, which could be introduced a bit later. 

General comment: Figures are not always introduced in the order of their numbering. Adjusting this might make things easier to follow.

L177  (𝜌 of 900 kg m-3 (Huss, 2013). We estimated the loss of ice volume within the 2013 reference polygon by multiplying the polygon area () with the median elevation change (∆ℎ0.5 ). We estimated the total mass loss error (𝜎∆𝑀 ) from two normalized error components; the total elevation change error (𝜎∆ℎ) derived from equation (2), and the mapping error of the 2013 glacier outline ), (adjusted from Shean et al., 2020): 

Some issues here with the parentheses - some are not closed, "area ()" is empty. 

L195 does the stated uncertainty include the time difference between the acquisition of the radar measurement and the DEM?

L214: Table S2: as mentioned above, can you comment on whether the relatively low number of detected outbursts prior to 1985 is related to a lack of cloud free satellite imagery? Do you have enough images from those years to determine that there were no outbursts?

L235 The post-flood levels decreased in a similar manner and dropped below the DEM-derived lake level of 197 m h.a.e. in 2016 (Fig. 2c). Satellite images show that the lake continued to decrease in width in the following years, indicating that the postflood lake levels have further dropped since then (Fig. S5)

Missing word? “..show that the lake level continued to decrease”?

It would be helpful to add a sentence or two here that clearly explains why the time series in Fig 2 b and c stop in 2016 (no DEM showing lake levels below 197m?)

In the methods you state: “We estimated outburst volumes...using the mapped lake area outlines and the 2-m resolution ArcticDEM from 2020-09-11. This DEM (digital elevation model) shows the lake at the minimum water level at 197 m h.a.e. (height above WGS84 ellipsoid) and has the smallest glacier extent within the available ArcticDEM time series (Table S1). ….Between 2016 and 2023, there are no elevation measurements for post-flood levels below the 2020 ArcticDEM lake level, hindering the approximation of outburst volumes” 

I suggest mentioning this again in the section discussing the results in Fig 2 to make it easier for readers to follow. 

Fig 4, caption: The high positive values on the proglacial delta in the left panel are an artefact from cloud cover in the 2016 DEM

I suggest marking this in the Fig. like you did for the other features

Panel a, right panel: is the error for “sediment deposition” that points south correct? The deposition is not very apparent. (I think this is explained later in Sec 4.4. but I find it hard to see in the figure)

L270 (𝜎∆ℎ 

Close the parenthesis

L292 define IPR

L335 Our estimates are based on only ~11 km2 335 of the ablation zone and do not estimate the mean ice loss rate of the entire glacier surface. Yet, we consider the elevation changes across the dam region to be most relevant for investigating the influence of local glacier changes on the size and drainages of Desolation Lake. 

I think this warrants a bit more explanation. Why do you consider the elevation change in your investigated section the most relevant? Is there a reason other than it being closest to the lake?

L352 Thus, large parts of the surface lowering are likely contributed to surface melt, eventually causing the thinning of Lituya Glacier

This reads a bit odd, maybe change “contributed” to “attributed” or rephrase 

L362 I suggest stating where these lakes are (countries)

L423 while the glacier front of Fairweather Glacier remained largely within a range of ~240 m. 

Range of what? Is this in relation to some reference point?

L521 We argue that ice loss and the increase in accommodation space following frontal ablation are the key drivers of lake growth, rather than accelerated surface melt.

This sounds like the two factors are mutually exclusive. Are they? I find it a bit confusing to use the phrases “ice loss” and “accelerated surface melt” as two seemingly contrasting processes. Perhaps add a sentence or two to qualify, or consider rephrasing. “Glacier retreat” would indicate both ice loss and the increase in accommodation space for the lake (=space where the glacier no longer is). Alternatively, you might focus the explanation more on the difference between frontal ablation and surface ablation.