West and Bockley carry out an evaluation of vertical heat flux and Arctic sea ice evolution in a set of recent climate models with reference to observations from Ice Mass Buoys.  The work documents a variety of differences between models and between models and observations and as such, informs model developers what to focus on going forward.  I believe with minor revision, the work is appropriate for publication in Geoscientific Model Development. 

The authors make no mention of the possible differences between thermodynamic and mechanical (ice rafting) ice growth.  I have been told by ice experts that the thicker ice classes are most certainly created by rafting, not basal growth.  Perhaps their focus on the IMB data (that are rarely if ever deployed in really thick floes) makes this point moot.  But it might be worth a mention.

In the similar vein of mechanical influences, I wonder what impacts leads in the ice cover have on model state evolution.  In the one modeling paper I did that utilized IMB data (Toole et al., JGR 2010), the summer basal melt was virtually totally accounted for by ocean heat gain by solar radiation into leads.  Heat conduction through the ice was of secondary importance. 

This is no doubt beyond the scope of what the authors wish to discuss, but I would have appreciated a few lines explaining how heat flux between ocean and ice is derived in the models.  I’m particularly interested in this for the mushy-layer models where I wonder how ice-ocean stress is conducted through a mushy layer.

Lastly, going beyond the proposal that future MIPs include more information about heat fluxes, I wonder if the authors might offer thoughts on what improvements to model parameterizations are needed, and perhaps what observations are needed to better identify model shortcomings.

I close with some small issues:

Line 11: might be helpful to detail what specific fluxes are being evaluated.   From the following sentence, one might assume the focus is heat fluxes, but ice-ocean, air-ice, air-sea, ??? 

Line 15: just to check, “realistic” or “unrealistic”?  From the context, I am thinking the latter is intended.

Line 21: similarly, do you intend to say “underestimate” or “overestimate”? 

Line 26: I don’t follow why the mean state and future trend are “closely related.”  I guess I’m thinking of a positive correlation.  If thicker ice melts more than thinner ice, wouldn’t a present day overestimate of ice thickness imply a greater decrease (i.e., negative rate of change in ice thickness) over time (a negative correlation)?

Line 53: I don’t understand what melt, growth and conduction fluxes are.  Are you talking about heat fluxes associated with melt and growth? 

Top of page 3: are these model quantities available at each model grid point? 

Line 78: please clarify if the penetrating solar radiation mentioned here is through the ice or into the water within leads. 

Line 110: I think these are “atmospheric” pressure sensors.  Aside: absent an in-water pressure sensor at the base of the IMBs, the freeboard of the supporting ice floe cannot be determined by IMBs.  All of their reported variations in surface and basal elevations are thus relative to the IMB body. 

Line 119: what is this “reference layer”?  Same as mentioned at the top of page 5?

Figure 1: I find the term “Arctic Ocean region” confusing, in part because the label in the figure is over a yellow background region, not blue as noted in the caption.  I wonder if calling the North Pole and Beaufort Sea areas “subregions” might help?

Line 320: isn’t the quantity estimated the time rate of change of the heat content?  d/dz (vertical  heat flux) equal to d/dt (Heat Content).  I don’t know what a “heat storage flux” is.