Parrenin et al. report a 2.5D "flowtube" model that utilizes a coordinate transformation that greatly improves the numerical efficiency. This coordinate transformation was developed in previous publications roughly a decade ago, so the primary new aspect of this work is providing the model code so that others can more easily use the model. This paper is well suited for Geophysical Model Development.

The manuscript is clearly written and the primary equations and assumptions are well described and justified. The figures are informative, and are mostly auto-generated from the code. There is no particular scientific conclusion to the paper, which is ok since that is not the primary purpose. The application to EDC-BELDC is appropriate and demonstrates the model capabilities.

I have used this model before and found it useful, functional, and well documented.

I have only a few suggestions given below:

- The conclusion is missing text and should be expanded upon.

- In the abstract, intro, and conclusion, the coordinate transformation should be described with an additional sentence. What is the gist of the coordinate transformation?

- L21 - change "most important" to "largest" since "most important" is an opinion

- L22-25 - give references for each of these points and separate with semicolons rather than commas

- L26 - make "type" plural

- L50 - make "scheme" plural

- L234 - change "in front of" to "compared to"

- L256 - change ">15km" to ">20km" to be consistent with other locations in the paper

- Figure 1. I don't understand the labeling of "Q(x)" beneath the ice sheet, should it be m(x)? The caption could also use more description of what the symbols represent.

- Figure 5. Can you describe why the red dashed lines in the top panel for the core sites don't reach the bottom of the graph? I think this is because the model domain gets to older ages than is actually found at the ice core sites, but it isn't clear.

- Figure 6 - I think added subpanels with the horizontal flux shape function plotted for each core site would make the figure more interpretable

- Figure 9 - mention in Figure 9 caption that the vertical thinning functions at EDC and BELDC are shown in Figure 10