Dear Authors

Thank you for the revised version of your paper. Overall, the reviewers performed a positive evaluation of your paper and your response to their comments appears adequate. I am therefore inclined to accept your paper but I would first request that you please consider the following minor changes.

Lines 161-163. That Br and I concentrations are not much affected by photochemistry would be better understood if the fairly high accumulation rate were mentioned at the same time. Presently, it is only mentioned in the subsequent paragraph, too late to be convincing upon reading.

Line 292. Cannot “Heterogeneous reactions on sea salt particles and seas-salts on sea ice” be part of the bromine explosion?

Line 297. Please consider replacing “proportion to” by “factor by”, if I understand you correctly.

Section 4.1. Would it be useful to discuss also the fraction of first year sea ice as an important determinant of the Br excess? See [Simpson et al., 2007], whom you cite.

Figure 5. How about adding a Na smoothed line for homogeneity and ease of comparison?

Figures 6 and 7. How about XY graphs of Br and I vs. sea ice area? These would be informative to visualize the scatter. Indeed, although interesting and significant, the correlations you obtain are not very high and seeing the error made in using these correlations would be very useful. I am sure you realize that many other factors determine excess Br, and that, although very interesting, excess Br is a good but not excellent proxy for sea ice area. I believe it is important not to mislead the quick reader as to the quality of the relationship.

In that vein, I would also highly recommend to modify your abstract and indicate the value of the correlation coefficients that you obtain. You state “These two halogens are therefore good candidates for extended reconstructions of past sea ice changes in the Arctic.” This may be perceived as somewhat exaggerated. I am convinced of the interest of your study but please do not try to oversell it. Given the correlations found (which are quite interesting), you will probably agree with me that using excess Br or I as a proxy for sea ice extent will bear a significant error. This has to be made clear in the abstract.

Thank you for you attention to these few points.


Reference

Simpson, W. R., D. Carlson, G. Honninger, T. A. Douglas, M. Sturm, D. Perovich, and U. Platt (2007), First-year sea-ice contact predicts bromine monoxide (BrO) levels at Barrow, Alaska better than potential frost flower contact, Atmos. Chem. Phys., 7, 621-627.

Dear Authors,

Thank you for your revised manuscript, which I am pleased to accept for publication in The Cryosphere, provided you make the very minor technical corrections detailed below.

Line 165 : please add average: the relatively high average accumulation rate

Line 302: please replace “factor by” with “factor by which”

Fig 4. Thanks for adding Fig 4, this is truly very useful for the reader to appreciate the scatter of your data. However, please add the units. For example log(Br, ng/g). Same for the X axes.

Thank you for submitting your work to The Cryosphere.

Florent Domine