Preprints
https://doi.org/10.5194/cp-2023-97
https://doi.org/10.5194/cp-2023-97
03 Jan 2024
 | 03 Jan 2024
Status: this preprint is currently under review for the journal CP.

Exploring the causes of multicentury pluvials in the Altiplano with a climate modelling experiment

Ignacio A. Jara, Orlando Astudillo, Pablo Salinas, Limbert Torrez-Rodriguez, Nicolás Lampe, and Antonio Maldonado

Abstract. Proxy records have long documented the existence of multicentury hydroclimate anomalies in the Altiplano of South America. However, the causes and mechanisms of these events are still largely unknown. Here we present the results of an innovative climate modelling experiment that explores the oceanic drivers and atmospheric mechanisms conducive to long-term precipitation variability in the southern part of the Altiplano (18–25° S). For doing so, we performed 100-yr-long hydroclimate simulations using a regional climate model forced by climatological conditions that resulted in pluvial December-January-February (DJF) seasons during historical times. Our modelling simulations produce long-term negative DJF precipitation trends for the southern Altiplano, suggesting that the mechanisms leading to historical wet summers are unable to sustain century-scale pluvials such as the ones documented in paleoclimate records. Our simulations show that permanent La Niña conditions, as well as SSTs anomalies in the southern tropical Atlantic, progressively reinforce upper and lower-troposphere features that inhibit moisture transport towards the Altiplano. We further observed increases in March-April-May precipitation, suggesting the emergence of a long-term seasonal shift. Our simulations reproduce a sustained northward migration of the Atlantic trade winds, resulting in contrasting hydroclimate responses between the Altiplano and the tropical Andes. The atmospheric processes associated with these differences provide a useful analogue for explaining divergences in proxy records. Our study shows how regional climate modelling can be used to test paleoclimate hypothesis, emphasizing the necessity of combining proxy and modelling data to improve our understanding of long-term hydroclimate change.

Ignacio A. Jara, Orlando Astudillo, Pablo Salinas, Limbert Torrez-Rodriguez, Nicolás Lampe, and Antonio Maldonado

Status: open (until 13 Mar 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-97', Anonymous Referee #1, 31 Jan 2024 reply
    • CC1: 'Reply on RC1', Orlando Astudillo, 09 Feb 2024 reply
Ignacio A. Jara, Orlando Astudillo, Pablo Salinas, Limbert Torrez-Rodriguez, Nicolás Lampe, and Antonio Maldonado
Ignacio A. Jara, Orlando Astudillo, Pablo Salinas, Limbert Torrez-Rodriguez, Nicolás Lampe, and Antonio Maldonado

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Short summary
We conducted a regional model experiment that simulates a century of December-January-February (DJF) precipitation change in the South American Altiplano. Despite that we forced our modelling runs with conditions that produced humid DJF seasons today, our simulations show continuous reductions in precipitation over the Altiplano, suggesting that the climate drivers of modern-time humid seasons might not be the same that caused the extended humid periods observed in Holocene records.