the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Dec 2024
Evaluation of regional climate features over Antarctica in the PMIP past1000 experiment and implications for 21st-century sea level rise
Abstract. Surface mass balance (SMB) of the Antarctic Ice Sheet (AIS) is an important contributor to global sea level change. Past climates provide an opportunity to evaluate model performance outside the range of recent observed climate variability. We look to the Last Millennium (850–1850 CE) as a period of relative climate stability to understand what processes control natural variability in SMB, distinct from anthropogenic warming. With evidence for large regional differences in climate trends from ice core proxy records, paleo-simulations need to be validated over long timescales to assess if they capture those regional variations. The drivers for such regional variations during the Last Millennium and present day remain uncertain, demonstrating the need for a regionally focused study. Here, we evaluate model performance by comparing available Paleoclimate Modelling Intercomparison Project (PMIP) past1000 models and the CESM Last Millennium Ensemble (CESM-LME) to four sets of Last Millennium Antarctic proxy-based reconstructions that are most relevant to the SMB: snow accumulation, surface air temperature (SAT), sea surface temperature (SST) and Niño 3.4 index, using a multi-parameter scoring method. Our results show that, overall, PMIP past1000 models reasonably capture SATs estimated in the proxy record, but show poor skill with respect to reconstructed regional snow accumulation means, trends and variability and the Niño 3.4 index. Models show some skill but a slight cold bias in simulating Southern Ocean SST. The overall best-scoring PMIP past1000 models for regional climate features of Antarctica and the Southern Ocean are the CESM-LME mean and CSIRO-Mk3L-1-2. CESM-LME predicts higher SMB by 2100.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2412 KB) - Metadata XML
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Supplement
(978 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-3638', Anonymous Referee #1, 17 Dec 2024
- AC1: 'Reply on RC1', Vincent Charnay, 03 Jun 2025
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RC2: 'Comment on egusphere-2024-3638', Anonymous Referee #2, 07 May 2025
The authors present a comprehensive and well-executed evaluation of regional climate features—such as snow accumulation, surface air temperature (SAT), sea surface temperature (SST), and the ENSO index—that influence surface mass balance (SMB) over Antarctica. The comparison across multiple PMIP past1000 models and CESM-LME, alongside proxy reconstructions, is thorough and highlights important mismatches between models and observations. A key takeaway is that no single model performs consistently well across all variables, and even the best-performing model (CESM-LME) only marginally outperforms others in projecting future SMB increases.
Overall, the manuscript is well written, and I don't have any major concerns.
Minor comment:
I believe the manuscript would benefit from a clearer articulation of the scientific implications of its findings. While the motivation to understand SMB variability is well established in the introduction, the discussion section could more explicitly address how the model evaluation enhances our understanding of SMB and its relevance for future sea level projections. For instance, the abstract notes that CESM-LME predicts higher SMB by 2100, but the implications of this projection are not explored. To what extent does an increase in SMB contribute to sea level rise? These are critical questions that would help contextualize the study’s broader significance. Based on the title of the paper, I was expecting a stronger emphasis on these implications. At present, the manuscript is heavily focused on model evaluation (which is good), but the connection to the larger scientific or societal relevance—particularly in the context of sea level rise—is underdeveloped.Line 361–363: Not sure if the statement “all models generally agree” is true here. For example, CESM-LME shows no change in coastal East Antarctica, while other models show notable anomalies. Consider softening this claim.
Line 372–373: Again, all models mostly agree for West Antarctica, but not for East Antarctica.
Line 378: Consider removing the parentheses around “Bellingshausen and Weddell Seas”.
Line 381: “.......changes in the West Antarctica”
Line 381–384: This point appears to repeat content from lines 362–363.
Section 5.3: I think much of this section could be moved to results.
Citation: https://doi.org/10.5194/egusphere-2024-3638-RC2 - AC2: 'Reply on RC2', Vincent Charnay, 03 Jun 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-3638', Anonymous Referee #1, 17 Dec 2024
- AC1: 'Reply on RC1', Vincent Charnay, 03 Jun 2025
-
RC2: 'Comment on egusphere-2024-3638', Anonymous Referee #2, 07 May 2025
The authors present a comprehensive and well-executed evaluation of regional climate features—such as snow accumulation, surface air temperature (SAT), sea surface temperature (SST), and the ENSO index—that influence surface mass balance (SMB) over Antarctica. The comparison across multiple PMIP past1000 models and CESM-LME, alongside proxy reconstructions, is thorough and highlights important mismatches between models and observations. A key takeaway is that no single model performs consistently well across all variables, and even the best-performing model (CESM-LME) only marginally outperforms others in projecting future SMB increases.
Overall, the manuscript is well written, and I don't have any major concerns.
Minor comment:
I believe the manuscript would benefit from a clearer articulation of the scientific implications of its findings. While the motivation to understand SMB variability is well established in the introduction, the discussion section could more explicitly address how the model evaluation enhances our understanding of SMB and its relevance for future sea level projections. For instance, the abstract notes that CESM-LME predicts higher SMB by 2100, but the implications of this projection are not explored. To what extent does an increase in SMB contribute to sea level rise? These are critical questions that would help contextualize the study’s broader significance. Based on the title of the paper, I was expecting a stronger emphasis on these implications. At present, the manuscript is heavily focused on model evaluation (which is good), but the connection to the larger scientific or societal relevance—particularly in the context of sea level rise—is underdeveloped.Line 361–363: Not sure if the statement “all models generally agree” is true here. For example, CESM-LME shows no change in coastal East Antarctica, while other models show notable anomalies. Consider softening this claim.
Line 372–373: Again, all models mostly agree for West Antarctica, but not for East Antarctica.
Line 378: Consider removing the parentheses around “Bellingshausen and Weddell Seas”.
Line 381: “.......changes in the West Antarctica”
Line 381–384: This point appears to repeat content from lines 362–363.
Section 5.3: I think much of this section could be moved to results.
Citation: https://doi.org/10.5194/egusphere-2024-3638-RC2 - AC2: 'Reply on RC2', Vincent Charnay, 03 Jun 2025
Peer review completion
Journal article(s) based on this preprint
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Vincent Charnay
Daniel P. Lowry
Elizabeth D. Keller
Abha Sood
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2412 KB) - Metadata XML
-
Supplement
(978 KB) - BibTeX
- EndNote
- Final revised paper