| 06 Aug 2026
High-resolution spatio-temporal variability of surface albedo on the glaciers of Hurd Peninsula, Livingston Island (2018–2025): controls by snow metamorphism, surface impurities and terrain roughness
Abstract. Surface albedo is a primary control on the energy balance of maritime Antarctic glaciers, yet its fine-scale spatial and temporal variability remains poorly constrained. Here we present a multi-campaign broadband albedo dataset acquired on Hurd Peninsula (Livingston Island, South Shetland Islands) during four austral summer field seasons (2018, 2019, 2024, 2025), using a portable albedometer mounted on a snowmobile traverse at 5 s sampling resolution. Under clear-sky conditions, surface albedo undergoes exponential decay described by α(t) = α0e−kt with k = 2.24 × 10−5 5 s−1 (R2 = 0.98), driven by wet-snow metamorphism and confirmed independently by time-lapse microscopy and field spectroradiometry. A statistically significant positive interannual trend in surface albedo (+0.016 yr−1, R2 = 0.57) is documented over the study period, most pronounced at elevations below 200 m above sea level (a.s.l.), and attributed to increased summer snowfall frequency associated with the regional intensification of precipitation. Residuals between observed and modelled albedo reveal two distinct classes of spatial forcing: (i) biological and mineral impurities — Chlamydomonas nivalis blooms recurrently concentrated below 100 m a.s.l. and cryoconite deposits near 250 m a.s.l. — and (ii) terrain roughness and slope, whose correlation with albedo residuals reverses sign between years of contrasting snow cover. An integrated albedo–altitude profile (n = 4,219) identifies the 200–260 m a.s.l. band as the locus of maximum variability, coinciding closely with the mean equilibrium-line altitude (ELA) of Hurd Glacier (∼203 m a.s.l.). These results demonstrate that broadband albedo on maritime Antarctic glaciers cannot be adequately characterized by temporal decay models alone, and that impurity distribution, terrain geometry, and proximity to the ELA must be explicitly accounted for in energy balance and remote sensing applications.
## Summary
This study focuses on the acquisition and analysis of in-situ spatio-temporal albedo measurements on an outlet glacier located in a maritime Antarctic setting. The study utlises in-situ measurements acquired during several austral summers between 2018 and 2025. This area sees frequent summer snowfall, which is reflected in the albedo records acquired; snow cover dominates the albedo variability, alongside (lesser) effects attributable to topographic variabiliity and the accumulation of dust and what is identified here to be red snow algae.
While the presentation quality of the manuscript is generally good and includes appropriate referencing, I have a number of major comments which appear to severely limit the potential of the paper to support the conclusions drawn therein. If I have simply misunderstood then I would welcome dialogue on why this is the case and would hope that the manuscript is updated accordingly to address these misunderstandings.
## Major comments
### Insufficient data to support temporal trend analysis.
As the authors note, at this study site there is substantial temporal variability in albedo as a result of frequent summer snowfall. This part of the variability analysis is fine. However, I do have concerns with trying to derive temporal trends from such a small number of temporal sampling points and without explicit consideration in the statistical analysis of the importance of sub-seasonal snowfall to albedo.
In my view if the authors wish to make any assertions about temporal trends in albedo, then different/complementary datasets are required. These could either be from automatic weather stations (although I appreciate that it sounds like these are unavailable), or from remote sensing if there are sufficient cloud-free observations each summer.
### Generalised applicability of the exponential decay function and its use to calculate residuals.
Based on a single measurement period of 40 minutes at a static location, the authors derived an exponential albedo decay function for snowy, clear-sky conditions which they appear to subsequently apply without discrimination to all albedo transects. I have multiple questions concerning this part of the analysis.
1. The authors note that this function was derived under clear-sky conditions. However, no further information is provided, for example day of year/specific date, time of day.
2. Furthermore, what about the surface energy balance at the time these observations were made? The decay of the surface is not only modified by radiative fluxes, it can be modified by other fluxes too; for example the case of weathering crusts in ablation zones (e.g. Schuster, 2001; Stevens et al., 2026).
3. It therefore remains unclear whether it is (always or ever) appropriate to apply this function of modelled albedo decay to each transect time series. insufficient information about the illumination conditions, time of day, day of year of each transect acquisition is provided to be able to assess this.
4. The P95 normalisation (L150 onwards) used to apply this function to each traverse lacks clear motivation. In particular, it is unclear to me why it is valid to take the 95th percentile of the entire traverse series (which is time-varying and so acquired at some time later than time=0) then use that to fix the albedo at time=0. In this respect I would suggest that the reader needs more information on whether there is any dependence of the speed of snow grain metamorphism in relation to the starting broadband albedo. Basically, if the broadband albedo at t=0 were ~0.8 instead of the (very low for snow) 0.54 stated here, then would the decay function found here still stand?
4. It's very unclear to me what insights the residuals plotted in Fig. 5 (right hand column) reveal, given that it isn't clear that applying the exponential model is appropriate.
5. The decay function is invoked as dependency for multiple downstream analyses, including for example L221 where it is stated that 'steeper and rougher terrain yielded albedo consistently below the model prediction in both years', and with its use to derive residuals to correlate against (Figs. 6 and 7). Yet it is completely unclear why this 'model prediction' is appropriate for thie use case.
6. To fully support the discussion and conclusions of Sect. 5.1 I would find it important to further reflect on representativeness of this single measurement set acquired on a single day. For example, is it typical of a normal day on Livingston Island, or were the specific energy balance conditions very rare for this area?
7. At L321-322, I do not understand why this 'residual analysis' permits to identify impurity signals?
### Identification of impurities
I have two key areas to follow up on here. First, as far as I understand, the identification was effectively done only visually, i.e. without follow-up laboratory analysis. It's unclear to me that this is adequate, particularly given the very limited pieces of 'photographic' evidence presented here rather than, for example, summary statistics of a dataset with sufficient statistical power. There is no detailed information provided about sampling protocols, number of samples, replicates, locations/times and so on. This information is critical to understand the reliability of these claims.
There are also specific issues with the analysis presented which revolve around a lack of clarity concerning the underlying surface type. For example, L330 talks of both snow and (cryoconite-contaminated) ice and refers to Fig. 9, yet Fig. 9 is labelled as 'snow surface impurities' for all three surface types. Yet it is essential to differentiate between snow and ice surfaces given their major structural differences. See an abundance of literature on the subject. Furthermore, this is important from the perspective of accurately identifying the algal species: as far as I'm aware, snow algae (i.e. Chlamydomons nivalis) does not live on bare ice surfaces, which are rather colonised by Ancylonema nordenskioldii and A. alaskanum.
## Minor comments
Graphical abstract: In the panel 'Observed albedo vs decay model', it isn't clear that what is being shown here is some kind of space-time substitution on the x-axis, i.e. the x-axis actually is time for the decay function but implicitly space for the observations. This seems problematic, especially for the graphical abstract.
Methods: How was the albedometer kept level on the traverses? Presumably it was not mounted in a gyroscope. Please provide an indication of the error associated with not keeping the albedometer levelled. (Though I note that a shadowing correction was applied)
Figure 1a: No information on background shading/image is provided.
Fig. 1 / Fig 5: What is the direction of the snowmobile tracks? This is important so that they can be interpreted along the time-elapsed axis of Fig. 5.
L119-124: contains some repetition of L109-111.
I struggled to understand the systemically lower albedo found at higher altitudes (>~270 m). Please reflect further on this analysis.
Fig 5: The last sentence of the caption contains a description which would be better placed in the Results.
L215-225: Too much repetition of statistics in the text that are found immediately below in Table 5 - it is likely okay simply to refer to the table instead of quoting the stats in the text.
Fig 8: Second sentence of caption has missing period. Third sentence to end of caption belongs in the Results text, not in the caption.
L276-279: this section seems confused. There are multiple references to the elevation zone 'below 200 masl' but also to the accumulation zone, which surely is ~the area above 200 m asl?
L280/281: Is there any reason preventing remote sensing measurements being used to accomplish the same task?
Figure A1, Table A1: I did not find any references to these appendixes in the main text.
Data availability: only the 2025 data are available at the link supplied.
Code availability: followed the github link provided. No public repositories are available at this link.
Statement on inclusion in global research: No 'in-country partners' are listed anywhere in the research. This statement feels like it was not written for this study.
## References
Schuster, Corinne Joanne, "Weathering crust processes on melting glacier ice (Alberta, Canada)" (2001). Theses and Dissertations (Comprehensive). 489.
https://scholars.wlu.ca/etd/489
Stevens IT, Cook JM, Chevrollier L-A, et al. The formation and evolution of the supraglacial weathering crust on the Greenland ice sheet. Journal of Glaciology. 2026;72:e30. doi:10.1017/jog.2026.10146