Review of “Spatial and temporal variations in rockwall erosion rates around Pigne d’Arolla, Switzerland, derived from cosmogenic 10Be in medial moraines at five adjacent valley glaciers” by  Katharina Wetterauer and Dirk Scherler

This is a well-written and informative manuscript. The study is well-embedded in the existing literature and the study sites, methods and data sets are described and analysed in detail. I would recommend it is published, subject only to a few minor points of clarification listed below.

1. The manuscript builds on a previous study (Wetterauer, 2022) but I was not clear how it adds to that study, other than expanding the data set from a single site (Glacier d’Otemma) to four other new sites (Glacier du Brenay, Glacier de Cheilon, Glacier de Pièce, and Glacier de Tsijiore Nouve). I would like to see a clear statement of what the addition of these new sites has added. The place to do this is probably around Line 69 of the manuscript.
2. Figure 1 could be improved. There are a lot words in the caption that should be in the legend or annotated on the various panels.
3. Line 188 “assuming an initial concentration of zero”: can we have some discussion of the validity (or otherwise) of this statement? Does it mean you assume that the original bedrock in the rockwalls had no exposure? This seems unlikely to me as presumably these were exposed above the glaciers over the last few millenia.
4. Line 208: I would like to see a statement about how representative (or otherwise) the samples are. How were the samples collected and how did you decide where to collect them? How did you ensure they represent the local environment at each point of the moraines?
5. Line 257 onwards: Please add an uncertainty estimate for the velocities here and elsewhere.
6. Line 305 “We acknowledge that our reconstruction of glacier surface velocities and elevations contains several sources of unquantified uncertainties”: can you say more about how these unquantified uncertainties are a limitation and how this then plays out? Where is it later discussed? (mentioned again on Line 405).
7. Line 576: What does “provides systematic results” mean?
8. Conclusion iv (line 596): I am not sure you can say this (that the source walls are unaffected by any major climatic, tectonic or lithological differences) because the temporal records you have derived are so short by comparison.

Reference:

Wetterauer, K., Scherler, D., Anderson, L.S., and Wittmann, H.: Temporal evolution of rockwall erosion rates derived from cosmogenic nuclide concentrations in the medial moraines of Glacier d’Otemma, Switzerland, Earth Surf. Proc. Land., 47, 2437-2454, https://doi.org/10.1002/esp.5386, 2022

Review of Wetterauer and Scherler, “Spatial and temporal variations in rockwall erosion rates around Pigne d’Arolla, Switzerland, derived from cosmogenic 10Be in medial moraines at five adjacent valley glaciers”

This paper describes a new study extending the approach of measuring glacier headwall/sidewall erosion rates using the 10Be concentrations in medial moraines. The authors combine new measurements with published data on multiple Alpine glaciers that flow more or less radially from a central massif, enabling comparisons on aspect, slope, glacier size, etc. Glacier surface velocity tracking is used to constrain debris transport rates due to ice flow, which enables assignment of specific samples to times in the past spanning ~200 yrs in the longest case. These are supplemented by various historical maps and other documents to evaluate changes due to ice loss and lowering along headwalls. Thus both spatial and temporal trends are assessed. 

The manuscript is very well written and organized. The figures are well drafted and useful. It is clear that the researchers worked hard to evaluate the potential impacts of the common sources of error associated with these methods (particulalry admixture of subglaical debris), and reported the results with the appropriate caveats. The findings that hint at the increase in rockfall erosion rates across the LIA but little change since are interesting and potentially quite useful for past climate evaluations; I’m not sure of any other way to get such a record. The results that show a dependence of rock wall erosion rates on aspect and a stronger one on slope reinforce physical models of rockfall erosion.

It’s uncommon that I can’t find something to nitpick in a paper, but really, this is ready to be published in my evaluation. Very nice study.

-DW