the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Mar 2024
Opposing changes in subpolar ocean heat content due to meridional heat advection driven by the Southern Ocean wind anomaly
Abstract. The global ocean has been warming significantly due to rapid climate change, leading to conspicuous changes in the subpolar Southern Ocean. Our study reveals that the heat exchange between Antarctic and subtropical oceans driven by wind, which plays an important role in modulating changes in regional ocean heat content (OHC) through meridional heat advections. In this study, we used the observed objective analysis and reanalysis datasets to explore the changes in subpolar ocean heat content and analyze attributions to the remarkable regional discrepancy. We found a notable difference in OHC trends between the Atlantic–Indian sector and the Pacific sector, which could be attributed to the inverse meridional heat advection caused by wind anomalies. Atlantic–Indian sector warming was significantly modulated by increasing meridional heat advection induced by the poleward westerly wind. In the Pacific sector, the enhanced wind resulted in substantial cold-water advection equatorward, causing significant cooling. These opposite advections are also occurring with the corresponding regional front movement, which also indicates the meridional heat exchange between oceans. This study highlights that wind anomalies play an important role in modulating the heat exchange between Antarctic and subtropical oceans. Consequently, the atmospheric forcing may become more significant to the heat redistribution in the Southern Ocean in the warmer future.
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Status: closed
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RC1: 'Comment on egusphere-2024-816', Anonymous Referee #1, 25 Apr 2024
The paper is well-structured and presents significant findings. Although the authors attempt to interpret the results in light of existing research, this area could be enhanced. The results have potential for publication, but the interpretation and discussion sections need substantial revision to meet the expected standards. I recommend accepting the paper, provided it undergoes major revisions. I also suggest a thorough review of the manuscript to refine the English writing and improve clarity.
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AC1: 'Reply on RC1', Ling Du, 08 May 2024
Dear Reviewer,
Thank you very much for your specific and helpful comments. Your valuable suggestions are very considerate to us. This document includes our replies to all your questions. All revises are in blue text in the manuscript. If these modifications are still insufficient, please point out the shortcomings, we will continue to improve. Thank you again for your time.
In addition, we take your comments about writing seriously. We reviewed the manuscript, and especially recheck the abstract. We also attach the previous polishing proof (Certificate of English language editing.pdf) of this manuscript provided by Let Pub service.
Best regards,
All Authors
-
AC1: 'Reply on RC1', Ling Du, 08 May 2024
-
RC2: 'Comment on egusphere-2024-816', Anonymous Referee #2, 01 May 2024
The Southern Ocean plays a critical role in modulating anthropogenic climate change through uptake of anthropogenic heat and carbon. In this paper, the authors examined the heat content changes in the Southern Ocean and tried connecting these changes to meridional heat exchanges due to surface wind changes. This is an interesting discussion. However, I am not convinced that these discussions on the causal relationships are robust (see my concerns below). Although the paper has potentials to become an interesting study, I don't think it is ready for further considerations at this stage.
[Major concerns]
- They claimed that they "found a notable difference in OHC trends between the Atlantic-Indian sector and the Pacific sector". However, the "Pacific sector" is defined as a region that covers only about a quarter of the real Pacific sector. If the whole Pacific sector is used, I don't think the OHC is decreasing. In any case, I agree that the OHC increase is not uniform in the Southern Ocean, but it is definitely not OK to manipulate the definition of basin sectors.
- Most of the explanations for how surface wind affect OHC changes are speculative without quantification. To explain the OHC changes, a budget analysis is required -- zonal heat advection or vertical heat fluxes, including air-sea fluxes, may be equally/more important, and different component may compensate for each other. The decomposition into isopycnal heaving and spicing changes is interesting, but the regional isopycnal movement is not necessarily related to meridional heat advections -- zonal convergences may also contribute to or even dominate isopycnal movements.
- [Figure 2 & discussions] The temperature/salinity differences in density coordinate cannot be compared directly to changes in depth/pressure coordinates. The hydrographical changes in density coordinate represent "spice" changes as defined in Section 2.
- [Lines 369-398]: I don't see significant wind stress curl changes over the period. I don't understand how these positive wind stress curl that last a few months affect the SAF position? If we consider the SAF as the southern boundary of the subtropical gyre, its position is more likely affected by the long-term mean position of zero wind stress curl. Do you see such changes? Also I don't think Amundsen Sea Low is play a role in the considered region.
[Minor comments]
- "subpolar": When we talk about the subpolar Southern Ocean, we are usually referring to the Weddell and Ross gyres, not the Southern Ocean between 40S and 60S.
- [Line 15]: What is an "inverse meridional heat advection"?
- [Line 17]: What is "poleward westerly wind"?
- [Figure 1 captions]: (c) the OHC changes should be OHC post 2005 minus OHC pre-1993.
- [Lines 183-189]: Why define such an index? Can you just use stratification?
- [Line 201]: The cooling is more widespread in WOA (Figure 1c). I don't understand this sentence -- what do you want to say by "it still attained -0.1 ZJ/decade"?
- [Figure 5]: What do "southward SAF" and "northward SAF" mean here?
- [Line 373-374]: What is a "north positive wind curl"?
- [Figure 9]: Do you calculate heaving and spicing in depth coordinate and then map to isopycnal coordinates?
- There are a number of grammatical errors in the writing that makes the paper a bit hard to follow. I would also suggest the readers to streamline their manuscript to make the discussion more concise.
Citation: https://doi.org/10.5194/egusphere-2024-816-RC2 -
AC3: 'Reply on RC2', Ling Du, 24 May 2024
Dear Reviewer,
Thank you very much for your illuminating and constructive comments. Your crucial comments help us a lot to improve this study. This document includes our replies to all your questions. All revises are in blue and green text in the manuscript. If these modifications are still insufficient, please point out the shortcomings, we will continue to improve. Thank you again for your time.
Best regards,
All Authors
-
EC1: 'Comment on egusphere-2024-816', Bernadette Sloyan, 08 May 2024
I suggest the authors carefully consider the reviewers comments. Both reviewers find that while this manuscript may have the potential to provide interesting results, currently the manuscript does not provide robust analysis to support their findings, I agree with the reviewers comments.
Citation: https://doi.org/10.5194/egusphere-2024-816-EC1 -
AC2: 'Reply on EC1', Ling Du, 20 May 2024
Dear Editor,
Thanks to you for taking the time to handle our manuscript. Thank two anonymous referees for taking the time to review our manuscript. We are very grateful for their crucial insights and constructive suggestions. We are checking the manuscript carefully and preparing detailed responses to each referee. All results would be carefully examined to clarify our scientific results. We will reply to each comment adequately in detailed files and try our best to revise our manuscript accordingly to a better version.
Best regards,
All Authors
Citation: https://doi.org/10.5194/egusphere-2024-816-AC2
-
AC2: 'Reply on EC1', Ling Du, 20 May 2024
-
EC2: 'Comment on egusphere-2024-816', Bernadette Sloyan, 08 May 2024
I suggest the authors carefully consider the reviewers comments. Both reviewers find that while this manuscript may have the potential to provide interesting results, currently the manuscript does not provide robust analysis to support the main points of the study, I agree with the reviewers comments.
Citation: https://doi.org/10.5194/egusphere-2024-816-EC2 -
AC4: 'Reply on EC2', Ling Du, 27 May 2024
Dear Editor,
Thanks to you for taking the time to handle our manuscript. We have revised the manuscript and submit the latest version. All results had been carefully examined to clarify our scientific results. We are looking forward comments from reviewers and editor to improve this study. Thank you again for your time.
Best regards,
All Authors
Citation: https://doi.org/10.5194/egusphere-2024-816-AC4
-
AC4: 'Reply on EC2', Ling Du, 27 May 2024
Status: closed
-
RC1: 'Comment on egusphere-2024-816', Anonymous Referee #1, 25 Apr 2024
The paper is well-structured and presents significant findings. Although the authors attempt to interpret the results in light of existing research, this area could be enhanced. The results have potential for publication, but the interpretation and discussion sections need substantial revision to meet the expected standards. I recommend accepting the paper, provided it undergoes major revisions. I also suggest a thorough review of the manuscript to refine the English writing and improve clarity.
-
AC1: 'Reply on RC1', Ling Du, 08 May 2024
Dear Reviewer,
Thank you very much for your specific and helpful comments. Your valuable suggestions are very considerate to us. This document includes our replies to all your questions. All revises are in blue text in the manuscript. If these modifications are still insufficient, please point out the shortcomings, we will continue to improve. Thank you again for your time.
In addition, we take your comments about writing seriously. We reviewed the manuscript, and especially recheck the abstract. We also attach the previous polishing proof (Certificate of English language editing.pdf) of this manuscript provided by Let Pub service.
Best regards,
All Authors
-
AC1: 'Reply on RC1', Ling Du, 08 May 2024
-
RC2: 'Comment on egusphere-2024-816', Anonymous Referee #2, 01 May 2024
The Southern Ocean plays a critical role in modulating anthropogenic climate change through uptake of anthropogenic heat and carbon. In this paper, the authors examined the heat content changes in the Southern Ocean and tried connecting these changes to meridional heat exchanges due to surface wind changes. This is an interesting discussion. However, I am not convinced that these discussions on the causal relationships are robust (see my concerns below). Although the paper has potentials to become an interesting study, I don't think it is ready for further considerations at this stage.
[Major concerns]
- They claimed that they "found a notable difference in OHC trends between the Atlantic-Indian sector and the Pacific sector". However, the "Pacific sector" is defined as a region that covers only about a quarter of the real Pacific sector. If the whole Pacific sector is used, I don't think the OHC is decreasing. In any case, I agree that the OHC increase is not uniform in the Southern Ocean, but it is definitely not OK to manipulate the definition of basin sectors.
- Most of the explanations for how surface wind affect OHC changes are speculative without quantification. To explain the OHC changes, a budget analysis is required -- zonal heat advection or vertical heat fluxes, including air-sea fluxes, may be equally/more important, and different component may compensate for each other. The decomposition into isopycnal heaving and spicing changes is interesting, but the regional isopycnal movement is not necessarily related to meridional heat advections -- zonal convergences may also contribute to or even dominate isopycnal movements.
- [Figure 2 & discussions] The temperature/salinity differences in density coordinate cannot be compared directly to changes in depth/pressure coordinates. The hydrographical changes in density coordinate represent "spice" changes as defined in Section 2.
- [Lines 369-398]: I don't see significant wind stress curl changes over the period. I don't understand how these positive wind stress curl that last a few months affect the SAF position? If we consider the SAF as the southern boundary of the subtropical gyre, its position is more likely affected by the long-term mean position of zero wind stress curl. Do you see such changes? Also I don't think Amundsen Sea Low is play a role in the considered region.
[Minor comments]
- "subpolar": When we talk about the subpolar Southern Ocean, we are usually referring to the Weddell and Ross gyres, not the Southern Ocean between 40S and 60S.
- [Line 15]: What is an "inverse meridional heat advection"?
- [Line 17]: What is "poleward westerly wind"?
- [Figure 1 captions]: (c) the OHC changes should be OHC post 2005 minus OHC pre-1993.
- [Lines 183-189]: Why define such an index? Can you just use stratification?
- [Line 201]: The cooling is more widespread in WOA (Figure 1c). I don't understand this sentence -- what do you want to say by "it still attained -0.1 ZJ/decade"?
- [Figure 5]: What do "southward SAF" and "northward SAF" mean here?
- [Line 373-374]: What is a "north positive wind curl"?
- [Figure 9]: Do you calculate heaving and spicing in depth coordinate and then map to isopycnal coordinates?
- There are a number of grammatical errors in the writing that makes the paper a bit hard to follow. I would also suggest the readers to streamline their manuscript to make the discussion more concise.
Citation: https://doi.org/10.5194/egusphere-2024-816-RC2 -
AC3: 'Reply on RC2', Ling Du, 24 May 2024
Dear Reviewer,
Thank you very much for your illuminating and constructive comments. Your crucial comments help us a lot to improve this study. This document includes our replies to all your questions. All revises are in blue and green text in the manuscript. If these modifications are still insufficient, please point out the shortcomings, we will continue to improve. Thank you again for your time.
Best regards,
All Authors
-
EC1: 'Comment on egusphere-2024-816', Bernadette Sloyan, 08 May 2024
I suggest the authors carefully consider the reviewers comments. Both reviewers find that while this manuscript may have the potential to provide interesting results, currently the manuscript does not provide robust analysis to support their findings, I agree with the reviewers comments.
Citation: https://doi.org/10.5194/egusphere-2024-816-EC1 -
AC2: 'Reply on EC1', Ling Du, 20 May 2024
Dear Editor,
Thanks to you for taking the time to handle our manuscript. Thank two anonymous referees for taking the time to review our manuscript. We are very grateful for their crucial insights and constructive suggestions. We are checking the manuscript carefully and preparing detailed responses to each referee. All results would be carefully examined to clarify our scientific results. We will reply to each comment adequately in detailed files and try our best to revise our manuscript accordingly to a better version.
Best regards,
All Authors
Citation: https://doi.org/10.5194/egusphere-2024-816-AC2
-
AC2: 'Reply on EC1', Ling Du, 20 May 2024
-
EC2: 'Comment on egusphere-2024-816', Bernadette Sloyan, 08 May 2024
I suggest the authors carefully consider the reviewers comments. Both reviewers find that while this manuscript may have the potential to provide interesting results, currently the manuscript does not provide robust analysis to support the main points of the study, I agree with the reviewers comments.
Citation: https://doi.org/10.5194/egusphere-2024-816-EC2 -
AC4: 'Reply on EC2', Ling Du, 27 May 2024
Dear Editor,
Thanks to you for taking the time to handle our manuscript. We have revised the manuscript and submit the latest version. All results had been carefully examined to clarify our scientific results. We are looking forward comments from reviewers and editor to improve this study. Thank you again for your time.
Best regards,
All Authors
Citation: https://doi.org/10.5194/egusphere-2024-816-AC4
-
AC4: 'Reply on EC2', Ling Du, 27 May 2024
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