Overall this is a very well-written, comprehensive and robust paper, which I very much enjoyed reading. It details particle tracking approaches in the model IGM and documents their application to a series of case studies. The paper documents major model developments and their validation. It is likely to be of significant interest to a wide range of users and researchers and has the potential to unlock numerous key research questions relating to past glacier dynamics. My comments are very minor and mostly editorial and are in the attached pdf. A couple of the figures need slight adjustments, but this is really polishing round the edges of an already strong paper. Very interesting to read and very interesting work - a pleasure to review.

This manuscript presents an interesting modelling experiment, which takes advantage of technological advancements to explore glacial sediment transport and deposition over long time scales (10,000s of years) for the entire Alpine Ice Field. The paper details the model advancements, and then uses a series of case studies to examine the validity of their results, as well as potential applications. Overall, the paper is well written, and I think it will be of interest to a wide range of disciplines. My only general comment is that the introduction section reads a bit more like a summary of the paper, rather than an introduction to the key topics. To make this paper more accessible to a wide audience, a little bit more background information is needed for example, Lagrangian tracking isn't defined; that may not be a familiar term to those outside of the modeling community).  My comments are all relatively minor and highlighted  on the attached PDF.