IWRA Executive Office

OS3f Regional and nationwide scenarios 2

abstract 692

The Amancay project: from decennal to interannual climate variability in tropical and subtropical South America

Author(s): Francoise Vimeux, Jean-Philippe Boulanger, Myriam Khodri, Josyane Ronchail, Abdel Sifeddine, Florence Sylvestre, Amancay participants

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Session: OS3f Regional and nationwide scenarios 2

Abstract The Amancay project, grouping together French and South American scientific teams, has been starting

four years ago. This project aims at understanding the climate varibility in tropical and subtropical South America

from the seasonal to the decennal timescale. Specifically, it focuses on deciphering trend from abrupt changes and on

comparing the different climate modes. Indeed, documentation of our climate for the recent period (the last centuries)

is needed to separate the natural from the anthropogenic component. Main questions recovered by the Amancay

project are: what is the local and the regional variability ? What are the teleconnexions between tropical and

subtropical areas for the regional climate variability ?
To answer those questions, four regions impacted by the

South American Monsoon have been studied : the Nordeste, the South of the Amazon basin, the Andes and the

Parana-Plata basin. We also focus on two specific time periods: the abrupt climate change in 1970 and the Little Ice

Age (LIA). Our approach combines (1) documentation from past climate archives (corals, lake sediments and ice

cores), (2) calibration of proxies to better interpret the climate archives using both modern observations and

modelisation, and (3) climate and hydrology modelisations with a hierarchy of models. The main results that we

present here are: (1) the abrupt feature in 1970 is a widespread event leading to a common moisturing of the tropical

and subtropical South America and (2) the LIA is significantly recorded both in the Andean and the Parana basin

climate archives but with different signatures: moist and cold conditions are shown in the Andes whereas lake

sediments exhibit dry conditions in the Parana basin. For both periods, we seek to understand the mechanisms that

can explain either local or common variations. For the later, the objective is to explore which kind of teleconnexions

occured both between our key regions in South America and with other regions (specifically, with the Pacific and

Atlantic Oceans).

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The Amancay project: from decennal to interannual climate variability in tropical and subtropical South America