Dear Joshua Cuzzone and co-authors,
This manuscript received two very positive reviews that highlighted the quality of the undertaken modelling study and the importance of assessing the role of spatial resolution in relation to bed topography for longer-term palaeo modelling studies (…when is resolution high enough?). Both reviewer had however also some critical points, although minor, that have in general been addressed very well and with care in the revised version and justified where needed.
Besides correcting/changing all the minor editing issues the revisions included:
1) clarifying and correcting details in model descriptions, including new references and a new figure in the supplements that the grids for the different resolutions
2) adding of moraine record (map of geologiocal chronology) in Fig. 6 which provides a clearer context of the modelling sensitivity studies to the geologic reconstructions.

Thus overall this manuscript is very close to publication, but while reading the revised manuscript I spotted some very minor issues that are listed below and should be addressed/corrected before final publication. I congratulate the authors for their interesting paper and would like to thank them for their supportive handling of the revision process.

Best regards
The editor, Andreas Vieli, 24 Feb 2019


Rather minor issues that should be considered

-p. 1 line 28: the sentence which has been changed to '…retreat that occurs…' has been newly added seems awkward and not make sense to me anymore. Retreat is simulated for all of them independent of the intersection with the basal bump…
rephrase.

-Both referees were asking for a visualization of mapped moraines (which you have nicely added) and setting the results more into this context which you justified why you have not done much to this.
I agree with your response that this paper is not about looking for/matching the modelling to the geologic chronology, but point maybe this could be made more clear/explicit upfront at the end of the introduction (maybe near p. 4 line 4-5) to not raise wrong expectations.

-p. 4 lines 14-15: '…still remains not commonly used…' seems awkward formulation, maybe change to '…is still not commonly used…' or ' …is still rarely used…'

-p. 5 line 4: I think it was not clear to referee 2 what is meant by 'interior' which I think is still unanswered, do you mean with interior the bed beneath the current ice sheet.

-p. 6 line 19: maybe add here, as asked by referee 2 that the inversion for the basal drag coefficient has been done for all 4 different resolutions independently.

-p. 7 line 20-21: this sentence does not quite work out with the given order. When reading I got the impression first that the Dirichlet boundary condition is also at the ice front. Maybe change the order a bit to:
'We impose a free-flux boundary condition at the front and Dirichlet boundary conditions for ….'

-p. 9 line 32: I minor point, I would move the reference to Fig 7 into the brackets '…flow lines (A through E; Fig. 7) across the domain.' as you only refer to the map with the flowlines and not the retreat results.

p. 11 line 32 AND line 33 AND page 12 line 3: the citation 'van Tatenhove…' at the beginning of the sentence should be CAPITAL 'Van…'

p. 13 line 1-2: 'with accurately' I assume you refer in relation to the geologic chronology which maybe should be clarified, e.g. '…or amount of retreat in relation to the observed moraines accurately,…'

p. 14 line 25: I would change the order of the words a bit: 'In ice sheet model, calving is often related …'

Fig 6 first line in caption: typo, should be 'Southern' not 'Sourthern'.

Supplementary figure S2: in caption it should be clearer to what location/spatial average the shown temperatures and SMBs refer to, I assume:
'Surface temperature and surface mass balance for each model AVERAGED along the respective flowlines shown in Fig 7.