Influence of sea-ice anomalies on Antarctic precipitation using source attribution in the Community Earth System Model

Wang, Hailong; Fyke, Jeremy G.; Lenaerts, Jan T. M.; Nusbaumer, Jesse M.; Singh, Hansi; Noone, David; Rasch, Philip J.; Zhang, Rudong

doi:https://doi.org/10.5194/tc-14-429-2020

Articles | Volume 14, issue 2

https://doi.org/10.5194/tc-14-429-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-14-429-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 2

Research article

|

04 Feb 2020

Research article |

| 04 Feb 2020

Influence of sea-ice anomalies on Antarctic precipitation using source attribution in the Community Earth System Model

Hailong Wang, Jeremy G. Fyke, Jan T. M. Lenaerts, Jesse M. Nusbaumer, Hansi Singh, David Noone, Philip J. Rasch, and Rudong Zhang

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Final revised paper (published on 04 Feb 2020)
Supplement to the final revised paper
Preprint (discussion started on 12 Jun 2019)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review', Anonymous Referee #1, 31 Jul 2019
- AC1: 'Response to comments from all three referees', Hailong Wang, 01 Oct 2019
RC2: 'Review of Wang et al.', Harald Sodemann, 05 Aug 2019
- AC1: 'Response to comments from all three referees', Hailong Wang, 01 Oct 2019
RC3: 'More robust exploration of the findings needed', Anonymous Referee #3, 12 Aug 2019
- AC1: 'Response to comments from all three referees', Hailong Wang, 01 Oct 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (04 Oct 2019) by Christian Haas

AR by Hailong Wang on behalf of the Authors (29 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Oct 2019) by Christian Haas

RR by Anonymous Referee #3 (26 Nov 2019)

RR by Harald Sodemann (09 Dec 2019)

RR by Anonymous Referee #1 (16 Dec 2019)

Suggestions for revision or reasons for rejection

The authors answered to all my comment and I acknowledge the large amount of work they did for improving their manuscript.

I recommend this article to be published in The Cryosphere after addressing the following minor suggestions :

With regards to Fig. S1-S4, I suggest to replace the 4 figures by 2 figures showing the differences between the variables (baseline simulation - ERA5), with hashes where significantly different, as for new Figures 3 and 4. A focus on large scale circulation variables only is sufficient, as ERA5 does not assimilate Precipitation and Evaporation.

Change the following paragraph accordingly: « Although these sensitivity simulations are not designed to represent present-day conditions, several essential model fields from the baseline simulation are compared to the fifth generation ECMWF reanalysis (ERA5, 1979-2018). The main purpose is to provide a context for the interpretation of model results that might also be valid for the recent historical period in terms of internal climate variability. The large-scale patterns of SIC, surface temperature, circulation (sea level pressure), precipitation, precipitable water, and horizontal moisture fluxes in the baseline simulation are comparable to those in the ERA5 reanalysis, as shown in Figs. S1-S4. »

With regard to the answer to my comment regarding SIC and SST, I do believe that it is a methodology error to take the mean of multiple models instead of the median.
In the answer: « Certainly, SIC in the ERA5 reanalysis reflects anthropogenic forcing already. Surface temperature differences are consistent with SIC differences. We don’t see any unrealistic boundary conditions that the referee concerned about. »
Of course by comparing averaged SIC over several years you cannot see the impact of averaging the SIC throughout several simulation. If you do the same for 1 month in ERA5 vs. 1 month in the baseline simulation, then you will see a huge difference of spatial patterns.
I do not ask for you to re-do the simulation, but at least to acknowledge that it might not be the best way to proceed, maybe for future work.

« Comparison to the corresponding decadal variability of these annual mean fields (Fig. S6), along with a Student’s t-test at 90% confidence, suggests that the significant regional differences in surface temperature, evaporation and precipitable water are mostly due to SIC/SST perturbations while changes in precipitation is influenced more by internal variability. »
Why do you use a Student’s t-test and not directly the estimate of decadal variability to hash the differences as significant?

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ED: Publish subject to minor revisions (review by editor) (17 Dec 2019) by Dirk Notz

AR by Hailong Wang on behalf of the Authors (03 Jan 2020) Author's response Manuscript

ED: Publish as is (10 Jan 2020) by Dirk Notz

AR by Hailong Wang on behalf of the Authors (10 Jan 2020) Manuscript

Short summary

Using a climate model with unique water source tagging, we found that sea-ice anomalies in the Southern Ocean and accompanying SST changes have a significant influence on Antarctic precipitation and its source attribution through their direct impact on moisture sources and indirect impact on moisture transport. This study also highlights the importance of atmospheric dynamics in affecting the thermodynamic impact of sea-ice anomalies on regional Antarctic precipitation.