Preprints
https://doi.org/10.5194/egusphere-2024-545
https://doi.org/10.5194/egusphere-2024-545
05 Mar 2024
 | 05 Mar 2024
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

A continental reconstruction of hydroclimatic variability in South America during the past 2000 years

Mathurin A. Choblet, Janica C. Bühler, Valdir F. Novello, Nathan J. Steiger, and Kira Rehfeld

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.

Mathurin A. Choblet, Janica C. Bühler, Valdir F. Novello, Nathan J. Steiger, and Kira Rehfeld

Status: open (until 02 May 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-545', Raphael Neukom, 09 Apr 2024 reply
Mathurin A. Choblet, Janica C. Bühler, Valdir F. Novello, Nathan J. Steiger, and Kira Rehfeld

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

Mathurin A. Choblet, Janica C. Bühler, Valdir F. Novello, Nathan J. Steiger, and Kira Rehfeld

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Short summary
Past climate reconstructions are essential for understanding climate mechanisms and drivers. Our focus is on the South American continent over the past 2000 years. We offer a new reconstruction, particularly utilizing data from speleothems, previously absent from continental-wide reconstructions. We use Paleoclimate Data Assimilation, a reconstruction method that combines information from climate archives and climate simulations.