the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Mar 2024
A continental reconstruction of hydroclimatic variability in South America during the past 2000 years
Abstract. Paleoclimatological field reconstructions are valuable for understanding hydroclimatic variability. While being similarly impactful on societies as temperature variability, hydroclimatic variability has still remained less in focus. However, reconstructing globally complete fields of climate variables lacks adequate proxy data from tropical regions like South America, limiting our understanding of past hydroclimatic changes in these areas. This study addresses this gap using low resolution climate archives, including speleothems, previously omitted from reconstructions. Speleothems record climate variations on decadal to centennial time scales and provide a rich dataset for the otherwise proxy data scarce region of tropical South America. By employing a multi-time scale Paleoclimate Data Assimilation approach, we synthesize climate proxy records and climate model simulations, capable of simulating water isotopologues in the atmosphere, to reconstruct 2000 years of South American climate. This includes surface air temperature, precipitation amount, drought index, isotopic composition of precipitation amount, and the intensity of the South American Summer Monsoon. The reconstruction reveals anomalous climate periods: a wetter and colder phase during the Little Ice Age (1500–1850 CE) and a drier, warmer period corresponding to the early Medieval Climate Anomaly (600–900 CE). However, these patterns are not uniform across the continent, with exceptions in northeastern Brazil and the Southern Cone, indicating regional variability. The anomalies are more pronounced than in previous reconstructions, but align with local proxy record studies, thus highlighting the importance of including speleothem proxies. The multi-timescale approach is essential for reconstructing multi-decadal and centennial climate variability. Despite methodological uncertainties regarding climate model biases and proxy record interpretations, this study marks a crucial first step in incorporating speleothems into climate field reconstructions, potentially enhancing insights into past hydroclimatic variability and hydroclimate projections.
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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
(13159 KB)
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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
(13159 KB) - Metadata XML
- BibTeX
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-545', Raphael Neukom, 09 Apr 2024
Dear authors
I was pleased to see a new hydroclimate reconstruction with improved method being presented in this manuscript and I read it with much interest. The study marks a valuable contribution to the field. I had some issues with the validation of the reconstruction, see my comments in the attached PDF. I hope my inputs are helfpul for the revision.
Best regards, Raphael Neukom
- AC2: 'Reply on RC1', Mathurin Arthur Choblet, 18 Jun 2024
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RC2: 'Comment on egusphere-2024-545', Anonymous Referee #2, 16 Apr 2024
This manuscript presents a new Common Era climate reconstruction of South America, generated via paleo data assimilation. The authors include speleothems in their methodology, a largely unused archive in paleo data reconstructions. The manuscript provides a detailed description of their DA methods, validation methods, and clearly discuss the methodological limitations. They use their climate reconstructions to examine climatological anomalies through time and compare their findings to existing DA products.
This manuscript was incredibly thorough and presents an exciting new advancement in the use of speleothem records in paleodata assimilation. I think the authors hit a good balance between interpreting their reconstruction and an honest discussion of the limitations/uncertainties. From my understanding of DA, the methodology and science seems sounds, and I believe the manuscript is nearly ready for publication. I focus my few comments here on organization and readability.
Appendix organization: In my opinion, I think the Appendices are out of order (e.g. appendix D is reference before appendix C). This makes navigating through the very lengthy supplemental information a bit challenging. I would recommend reordering the appendices as follows (A, D, C, B). I ran into a similar issue with the supplemental figures within Appendix A. There were several times where figures were referenced out of order (e.g. AF9 and 10 were referenced before AF 5-8).
Supplemental figures: The number of supplemental figures in Appendix A makes the manuscript a bit cumbersome to read. I also find that the authors extensively discuss many of their supplemental figures in the text. This makes me wonder whether some should be moved to the main text? While I acknowledge that this may make the flow a bit less elegant, I think it would help guide the reader as the manuscript touches on quite a few different topics. I will not recommend any specific changes here and leave this decision up to the authors.
Line comments:
Line 65 – Missing some detail on the drivers of speleothem d18O. E.g. are there any studies specific to South America that should be cited here? What about upstream rainout, cloud effects. Etc… Dansgaard is a good reference, but some additional works should be cited here.
Line 75 – topic sentence is a bit confusing – perhaps say ‘are excluded’ instead of ‘may be excluded’
Line 399 – Unless I missed it, I couldn’t find the definition of the Southern Cone
Citation: https://doi.org/10.5194/egusphere-2024-545-RC2 - AC1: 'Reply on RC2', Mathurin Arthur Choblet, 18 Jun 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-545', Raphael Neukom, 09 Apr 2024
Dear authors
I was pleased to see a new hydroclimate reconstruction with improved method being presented in this manuscript and I read it with much interest. The study marks a valuable contribution to the field. I had some issues with the validation of the reconstruction, see my comments in the attached PDF. I hope my inputs are helfpul for the revision.
Best regards, Raphael Neukom
- AC2: 'Reply on RC1', Mathurin Arthur Choblet, 18 Jun 2024
-
RC2: 'Comment on egusphere-2024-545', Anonymous Referee #2, 16 Apr 2024
This manuscript presents a new Common Era climate reconstruction of South America, generated via paleo data assimilation. The authors include speleothems in their methodology, a largely unused archive in paleo data reconstructions. The manuscript provides a detailed description of their DA methods, validation methods, and clearly discuss the methodological limitations. They use their climate reconstructions to examine climatological anomalies through time and compare their findings to existing DA products.
This manuscript was incredibly thorough and presents an exciting new advancement in the use of speleothem records in paleodata assimilation. I think the authors hit a good balance between interpreting their reconstruction and an honest discussion of the limitations/uncertainties. From my understanding of DA, the methodology and science seems sounds, and I believe the manuscript is nearly ready for publication. I focus my few comments here on organization and readability.
Appendix organization: In my opinion, I think the Appendices are out of order (e.g. appendix D is reference before appendix C). This makes navigating through the very lengthy supplemental information a bit challenging. I would recommend reordering the appendices as follows (A, D, C, B). I ran into a similar issue with the supplemental figures within Appendix A. There were several times where figures were referenced out of order (e.g. AF9 and 10 were referenced before AF 5-8).
Supplemental figures: The number of supplemental figures in Appendix A makes the manuscript a bit cumbersome to read. I also find that the authors extensively discuss many of their supplemental figures in the text. This makes me wonder whether some should be moved to the main text? While I acknowledge that this may make the flow a bit less elegant, I think it would help guide the reader as the manuscript touches on quite a few different topics. I will not recommend any specific changes here and leave this decision up to the authors.
Line comments:
Line 65 – Missing some detail on the drivers of speleothem d18O. E.g. are there any studies specific to South America that should be cited here? What about upstream rainout, cloud effects. Etc… Dansgaard is a good reference, but some additional works should be cited here.
Line 75 – topic sentence is a bit confusing – perhaps say ‘are excluded’ instead of ‘may be excluded’
Line 399 – Unless I missed it, I couldn’t find the definition of the Southern Cone
Citation: https://doi.org/10.5194/egusphere-2024-545-RC2 - AC1: 'Reply on RC2', Mathurin Arthur Choblet, 18 Jun 2024
Peer review completion
Journal article(s) based on this preprint
Data sets
Climate model and proxy input data for PaleoDA South America reconstruction Mathurin Choblet https://zenodo.org/records/10370001
PaleoDA South America reconstruction Mathurin Choblet https://zenodo.org/records/10622265
Model code and software
Multi-time scale Paleoclimate Data Assimilation for the reconstruction of South American Hydroclimate Mathurin Choblet https://github.com/mchoblet/paleoda_sa
Video supplement
Climate anomaly fields for South America during the Common Era Mathurin Choblet https://av.tib.eu/media/66877
South American precipitation and SASM variability during the Common Era Mathurin Choblet https://av.tib.eu/media/66879
South American precipitation and SASM variability during the Common Era (with speleothem anomalies) Mathurin Choblet https://av.tib.eu/media/66880
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Janica C. Bühler
Valdir F. Novello
Nathan J. Steiger
Kira Rehfeld
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(13159 KB) - Metadata XML