Dear authors, I have received the reviewer comments on your revised m/s and there are a still number of items that require attention. Several of these relate to inadequate explanation or unjustified conclusions, which require major revisions. The referee report is included below for your consideration.

Best regards, Ross Brown (ed.)

Reviewer report of revised m/s:
This manuscript has been improved, but not enough to justify publication. In particular, the main findings of this study, which consist of Figures 5 and 6, are not well illustrated by Figure 7 and 8. I understand it is challenging to elucidate why sea ice responses to the summer AD during the early and the late periods (Figs. 6a and 6b) are so much different, but the authors have not made any serious effort to elucidate the mechanisms.

(1) Calculating the net surface heat flux anomalies associated with the summer AD
The decrease in upward shortwave radiation (decreased albedo) is usually a dominant factor for the net surface heat flux (SW_up + SW_dn + LW_up + LW_dn + SHF + LHF). I cannot understand why the authors were not able to see the decreased net surface heat flux over the regions where SIC decreased. I would urge the authors to re-calculate the net surface heat flux anomalies during the summers of strong negative AD. The authors should be able to see a significant decrease in upward shortwave radiation at the surface (SW_up) over the regions where SIC is anomalously small even though the SIC reduction was primarily driven by winds. Also, the net surface heat flux anomalies over the land need not be plotted because we are focusing on the heat flux over the Arctic Ocean.

(2) Calculating the ice flux divergence using reanalysis data such as PIOMAS and ORAP-5
The authors should be able to calculate the wind-driven ice flux divergence anomalies associated with the summer AD using reanalysis data such as PIOMAS and ORAP-5. I understand that this study attempts to illustrate the processes using observations, but the suggested processes – the increased impact of summer AD on sea ice (Figures 5 and 6)– are not highly original as pointed out by the other Reviewer. Therefore, more quantitative analyses are required to justify publication.

(3) Pattern correlation between Fig. 4c and 4d
I still cannot see any significant difference in the AD's SLP pattern before (Fig. 4c) and after 1997 (Fig. 4d). More explanations are needed on the pattern correlation. While the pattern correlation coefficient 0.58 is not low, the authors argue that this value verifies a statistically significant difference between these two SLP patterns, which I cannot understand.

(4) Page 7 (lines 17 – 19): "the strong relationship with SIE is largely due to the change in the AD in the recent period"
It is difficult to understand how the authors could draw such as strong conclusion from the correlation coefficient.

(5) Page 8 (lines 1 – 2):
Again, Figure 6 is the main finding of this study, but comprehensive mechanisms were not suggested by the authors. Why are the recent ADs far more efficient in decreasing the SIC over the Pacific sector of the Arctic? I understand this is not an easy question to answer, but the authors need to provide mechanisms for this. I recommend utilizing sea ice model outputs such as PIOMAS and ORAP-5. For example, PIOMAS provides sea ice thickness changes associated with the ice flux divergence.

(6) Page 8 (lines 15 – 17)
I cannot see any clear difference in ice drift speed in the central Arctic between these two periods (Figs 8a and 8b).

(7) Page 9 (lines 19 – 27)
The suggested mechanism is highly speculative. I cannot understand why the anomalously low surface air temperature in the Atlantic sector of the Arctic is such an important factor for the wind-driven ice flux divergence over the Pacific sector of the Arctic.

Dear authors, Reviewer 1 has recommended some additional minor revisions to your paper prior to acceptance (included below). I look forward to your responses.

Best regards, Ross Brown

Reviewer 1 comments on revised m/s:

I’ve found that the first author has carefully responded to all of my questions in detail. I would like to thank the first author for his/her efforts for improving the manuscript. In particular, Figure S3, Figure R2 and Figure S4 are key figures that can nicely explain the different sea ice responses to the summer AD during the early vs. recent periods. Therefore, these plots need to appear as main figures and need to be illustrated more in detail. I am surprised to see that these nice plots (Figures S3, S4, R2) are in the supplementary information (or just for response to the reviewer).
I recommend publication subject to the following minor revision, but they are mandatory. I am willing to review the revised manuscript once more.
(1) Mechanisms: I cannot understand why it is important to show Figure 7 (surface air temperature anomalies associated with AD during the early and the recent periods). Instead, Figures S3, S4 (supp. Fig 3 and Fig 4) and R2 (response Fig 2) can nicely illustrate the mechanisms of sea ice loss during the summer AD events. These plots, Figures S3, S4 and R2 need to appear as main figures in the main text and need to be illustrated more in detail. Instead, I recommend moving the current Figure 7 (SAT anomalies) to supplementary information.
(2) In particular, Figure R2 nicely presents the intensification of Beaufort Gyre over the last decade. Please see Zhang et al. (2016). “The Beaufort Gyre intensification and stabilization: A model‐observation synthesis”. I strongly recommend introducing Zhang et al (2016) and explaining Figure R2 more in detail.
(3) Shortwave radiation (page 8, lines 19 – 20): “The surface heat flux anomalies are mostly contributed by the changes in the shortwave radiation terms (not shown)”
This result should be shown as a main figure and should be explained more in detail.
(4) Surface Albedo changes (page 8, lines 21 – 22): “The response of surface albedo becomes larger and much clearer..”
This is a main finding of this study and needs to be emphasized more – I strongly recommend

illustrating this finding in the Abstract.
(5) OLR (page 8, lines 11 – 14): “It is also found that the regressed OLR.. increase (decrease) of solar radiation”.
It is difficult to follow what the authors are trying to say. Do the authors argue that the increased OLR (less clouds) can melt more sea ice by increasing downward shortwave radiation at the surface? The increased downward shortwave radiation is usually compensated by the decreased downward longwave radiation. So, it is difficult to conclude that the increased OLR can melt more sea ice in the summer.
(6) Pattern correlation (page 7, lines 1 – 4): I appreciate adding this explanation. However, I suggest adding this calculation (r=0.76 as 95% confidence interval) in the supplementary information. Also, there is no illustration on the spatial pattern correlation of AD between the early and the recent periods: in the previous manuscript, the pattern correlation between Fig. 4c and 4d was written as 0.58, but in this revised version the correlation coefficient is missing. The authors may have accidently deleted this illustration.
(7) Page 7 line 20: “although the persistence of the observed AO index is too short to connect the winter AO with the summer sea ice extent”
I cannot understand this analogy. Williams et al (2016) emphasized the importance of AO- induced precondition not the persistence of seasonal AO.
(8) Color bars of Figure 2a and Figure 6: I suggest changing the color of Figure 2a and Figure 6 to reds (warm colors).
(9) The impact of transpolar drift on summer sea ice loss (page 2 lines 14 – 24): Park and Stewart (TC 2016) also showed that the southerly wind strengthening can effectively decrease summer sea ice cover over the Pacific sector of the Arctic.

Park, H.-S. and A. L. Stewart, 2016: An analytical model for wind-driven Arctic summer sea ice drift, The Cryosphere, 10, 227-244.
(10) Summery and Conclusion: This section need to be rewritten after adding Figures S3, S4 and R2 as main figures and after revising their illustrations on the mechanisms.

Dear Authors, following the recommendation of the reviewer I am very pleased to accept your paper for publication in The Cryosphere. Thank you for choosing TC and for your diligence in responding to the reviewer comments. The reviewer had one last piece of advice about Figure 8 (see comment below), which I leave to your discretion.

Congratulations!

Ross Brown (ed.)

Figure 8 (surface albedo): I think the color bar should be flipped for consistency with Figure 7. In Figure 7, net downward heat fluxes are shaded as warm colors.