|General comments: |
This is the revised manuscript accompanied by responses to the reviews of the original manuscript. The authors present the results of one component of a new earth system, namely the sea-ice. They first introduced a new grid generator for a tripolar grid. Then, they show initial results of the sea-ice component under normal-year-forcing (a kind of climatological forcing with synoptic scales sampled from a specific year) and different resolutions, including multi-scale analysis of the sea-ice deformation. Finally, they show the sensitivity of the dynamics of the model to the grid resolution and a long-debated parameter in the dynamics, namely the number of subcycling used in solving the viscous plastic equations.
The manuscript has improved in general but the English needs to be polished once more. The experiments are well described. The results are well presented and analyzed using existing diagnostic tools. More context for what the authors are aiming at would help however the reader as well.
1-I understand that the motivation in section 3.2 was to claim spatial multi-fractality in CICE which was originally disproved by Girard et al. (2009) => need to refer and discuss their results. Moreover, since the deformation field has not converged yet with respect to the NDTE parameter for TS015 and TS005 (ndte=240 in this section), I am curious to know the sensitivity to the parameter. In passing, I note that the sign of beta varies from negative to positive without clear explanations...
2-About the grid generation, I am grateful that the authors gave their rationale for developing their own generator, however this is done only in their response and is not reflected in the text. The reader is missing that context and is still left in the black. Notably the reference to the pioneered work of others is left to the appendix which leaves the wrong impression that the authors claim for the own the technique in the main part of the text. In their response, when comparing to the tri-polar ORCA grids, the authors imply that POP/CICE use a different and unique "U-fold", which I believe is a misconception. The POP manual (top page 46 of https://www.cesm.ucar.edu/models/cesm1.2/pop2/doc/sci/POPRefManual.pdf) does acknowledges that their tripolar grid is a courtesy of Madec (i.e. the ORCA grid). The only differences between ORCA and POP grids are in fact just technical (ORCA grids include a redundant row of points along the western, eastern and northern edges; ORCA grids accommodate both, what they call, F- or T-folds whereas POP grids exclusively rely on the F-folding technique, which the authors refer to "U-fold"). POP Manual also refers to Murray (1996) given below.
3-The authors in their response state that they found that their sea-ice state was more realistic with a change of ice strength formulation. I would refer them to Ungermann et al. (2017) where there is a discussion on the subject of Hibler (1979) vs Rothrock (1975).
4-"EVP rheology": Careful with using EVP as it were a different rheology in itself. The rheology remains VP (the constitutive laws) but EVP introduces artificially slow elastic waves for numerical (claimed) convergence. It is actually very akin to the pseudo-compressible method that was once in favour in computational fluid dynamics for solving for incompressible flows. Hunke use "EVP model", Koldunov et al. "EVP solution" and Bouillon et al. (2013) "EVP method".
5-ndte=960 does not seem to be enough in TS005 as we still see some blue in the CAA (fig.13), whereas, in the coarser resolution runs, the region is fully white. Same can be said for the central Arctic where it takes an increasing ndte to get the equivalent pattern in TS045, TS015 and TS005 respectively (.e.g the pattern of (TS005, ndte=240) is equivalent to (TS015,ndte=120), and that of (TS015, ndte=960) is in between to (TS045, ndte=240,960)). Same can be said from Fig.12. By the way, I like very much the colour scale in fig. 13, much easier to see patterns.
6-ndte is not indicated in fig.7-8-9. There is only one mention in the text that ndte=240 is used for all comparison of the ice deformation and scaling analysis until the next section. I would appreciate a reminder in the captions for fast browsing readers like me who like to go and forth through a paper and its figures.
7-Missing Figure S4?
8-Please include drags in Table B1.
9-Appendix B: should you take into account grid deformation in your calculation of deformation?
why TS005 on year 31 (or end of year 30) does not match that of TS015 in fig.4?
Abstract, line 5: I would "the" before "Community Earth System Model"
Abstract, line 8. "In specific" does not sound English
page 13, line 17-21: are still talking about fig.9? The term "cumulative" has been dropped here.
page 13, line 23 one instance of "CDF" remains (the others have been converted to "cumulative PDF") I don't think that the figure 9 has been corrected in that regard.
page 13, line 24-35: "Also, since we witness flatter cumulative PDF slopes in scaled datasets, we expect the “real” tails of cumulative PDFs at 2.4 km flatter than the modeling result from TS005, which have the slope of -1.0 for Dec. 20th, and -0.5 for Feb. 6th." Honestly, I don't understand the sentence anymore.
page 13, line 25 "we expect the “real” tails of cumulative PDFs at 2.4 km flatter than..." missing "to be" before "flatter"
page 13, line 27 "This is due to the temporal averaging on Eulerian grid points attenuates" misses a "which" before "attenuates"
page 14, line 24 "sea ice status" I think the authors meant "sea ice state"
page 14, line 25-36: the whole following sentence "Since the experiments in this study target at climatologlical sea ice states" could be phrased better (these experiment in this study aim at obtaining a climatologlically converged sea ice state?)
CORE instead of CORE2 in appendix B, line 21.
Girard, Lucas, et al. "Evaluation of high‐resolution sea ice models on the basis of statistical and scaling properties of Arctic sea ice drift and deformation." Journal of Geophysical Research: Oceans 114.C8 (2009).
Ungermann, Mischa, et al. "Impact of the ice strength formulation on the performance of a sea ice thickness distribution model in the A rctic." Journal of Geophysical Research: Oceans 122.3 (2017): 2090-2107.
Murray, Ross J. "Explicit generation of orthogonal grids for ocean models." Journal of Computational Physics 126.2 (1996): 251-273
Hunke, Elizabeth C. "Viscous–plastic sea ice dynamics with the EVP model: Linearization issues." Journal of Computational Physics 170.1 (2001): 18-38.
Bouillon, Sylvain, et al. "The elastic–viscous–plastic method revisited." Ocean Modelling 71 (2013): 2-12.
Koldunov, Nikolay V., et al. "Fast EVP Solutions in a High‐Resolution Sea Ice Model." Journal of Advances in Modeling Earth Systems 11.5 (2019): 1269-1284.