See attached .pdf.

In principle, this paper puts forward an exciting approach to compare conceptual ideas (ie geologically-driven) of landform (murtoo) formation with model predictions of hydrological settings. I see a lot of potential in such data-model exploration, particularly in relation to murtoos, since they are hypothesised to represent a transition in drainage style. However, I found this manuscript hard work due to “heavy” text, to the extent it is difficult to evaluate the significance of what has been found.

The manuscript is suitably constructed in its overall structure, but I struggled with a lack of direction and clarity in the writing. I wasn’t sure by the end of the Introduction, or the Methods, what the study was designed to explore, specifically, or what question was being asked; I had to read the Results to try and work out what the authors were actually trying to achieve (beyond a generality). Parts of the Discussion are more a summary of results than an exploration of their significance, and important insights are hidden or implied rather than explicitly stated. The same is true of the Conclusions, which ultimately don’t say anything concrete about what has been learned.

Besides the presentation...

1. The study area for modelling – and the distribution of murtoos – encompasses the whole Lake District lobe but the entire focus of the results is in the distal few 10s km. I realise the duration of the model effectively only considers one ice time-slice in the development of the whole lobe’s landform system, i.e. when the ice margin sits at Salpausselkä II. However, I think this needs to be stated explicitly, and I think the paper needs to discuss what the modelling findings imply for the formation of the other (most of the) murtoos in the domain. Do your results imply (or reject) that the upstream murtoos could form at the same time as those you consider in the near-marginal zone? Do your results imply that they must form time-transgressively (headward) during margin retreat?

Related, considering the distribution of murtoos over your model domain and the 40-60km band you focus your analysis on, one might wonder why (if) this particular time-slice is well-suited to the investigation – murtoo fields are actually rather few/sparse in this band, compared to elsewhere up the trunk of the Lake District lobe. Could you offer some justification for your approach?

2. Some recent work is suggesting that the YD may have experienced extreme seasonality, with relatively warm summers but extreme winters (e.g. Schenk et al. 2018 Nat Comms, 2020 QSR; Amon et al. 2022 Clim. Past). You replicate a Younger Dryas climate by lowering present monthly temperatures uniformly by 15°C. I wonder how extreme (or simply, different) YD seasonality would impact your results? How important is this choice of climate forcing for your hydrology conclusions?

3. Section 3.2 implies that only the zone 40-60km upstream of the ice margin is analysed, on the basis that this zone is favourable to murtoo formation. This seems a little circular to me. By focussing only here, do you not exclude the possibility of identifying conditions that would suit murtoo formation elsewhere? And exclude possible comparable hydrological/glaciological conditions elsewhere that may or may not support murtoos?

4. One of your results is rather surprising, which calls into question the appropriateness of comparing model output with specific mapped geomorphology: if channel discharge in late summer is significantly higher outside mapped meltwater routes (line 395) than where meltwater routes have been recorded, then this suggests the spatial distribution of channels predicted by the model is offset from where channels are known to have existed. This mismatch therefore also questions the validity of comparing hydrological parameters with where murtoos have been mapped or not mapped.

A further uncertainty in this regard concerns what is meant by a meltwater route? Section 3.2 suggests these are based on Ahokangas et al. As far as I understand, those authors keep eskers separate from their meltwater route classes – how did you treat eskers in your classification of “meltwater routes”?

At the very least, I think the presentation of results relating to geomorphological classifications needs to be preceded by a justification that the model performance is adequate in terms of what we know of the geomorphology: does the model do a good job of replicating channels? If it does, then it’s a valid tool to explore other landforms, and if not, then it’s not. This partly is presented in the Discussion (524-540) (though the earlier result I’ve queried here is not addressed) and I think would better serve the Results section if it were brought earlier. I also wonder, if the exact location of channels is sensitive to mesh geometry (536) then does this also not suggest that specific site-to-site data-model comparisons may not be appropriate?

5. Overall, the manuscript would have benefitted from a thorough proof-read – there are numerous typos, left-over words from earlier constructions, unit errors, muddled variables.

I note these in a rather lengthy list of line-by-line technical comments in the attached pdf, where I also identify issues with writing clarity, section by section, and suggest how the direction and framing of the work could be improved.