Sylvestre Florence. (2009). Moisture pattern during the last glacial maximum in South America. In :
Vimeux Françoise (ed.), Sylvestre Florence (ed.), Khodri Myriam (ed.). Past climate variability in South America and surrounding regions : from the last glacial maximum to the Holocene. [Dordrecht] : Springer, 3-27. (Developments in Paleoenvironmental Research ; 14). ISBN 978-90-481-2671-2.
Titre du document
Moisture pattern during the last glacial maximum in South America
Année de publication
2009
Type de document
Partie d'ouvrage
Auteurs
Sylvestre Florence
In
Vimeux Françoise (ed.), Sylvestre Florence (ed.), Khodri Myriam (ed.)Past climate variability in South America and surrounding regions : from the last glacial maximum to the Holocene
Source
[Dordrecht] : Springer, 2009,
3-27 (Developments in Paleoenvironmental Research ; 14). ISBN 978-90-481-2671-2
The Last Glacial Maximum (LGM) is still an exciting period of time for investigating ecosystem responses to climate changes since it corresponds to a steady state in a glacial world with maximum global expansion of ice-sheets, CO2 concentrations half those of today, temperatures up to 5?C cooler in the tropical lowlands, and precipitation regimes differed from today. South America is an ideal place to study these changes since climatic conditions during the LGM remain a matter of debate. There is general agreement that the temperature was cooler than today, but there is no consensus about moisture conditions, especially over tropical latitudes. This paper reviews terrestrial and near-shore marine records from South America between 10°N and 50°S during the LGM. Records are selected for their chronological control, their continuity around the LGM and their regional representativeness.This review aims to show how regional climates of the sub-continent have responded to orbital forcing as opposed to other global glacial boundary conditions, and how they are related to positions of the Intertropical Convergence Zone (ITCZ) and of the westerly belt. A clear pattern emerges for the northern and the southern latitudes, which were respectively drier and wetter, but in the tropical lowlands the pattern remains unclear. The characterization of this area is of particular interest because of the central role played by atmospheric convection centred on the Amazon basin. Modeling experiments argue for drier LGM tropical conditions but several lines of evidence contradict these results. Currently, moister conditions are explained by a glacial boundary forcing mechanism implying a southern shift of the ITCZ and a reinforcement of the South American summer monsoon (SASM), bringing more humidity to the tropical Andes as far as southern Brazil. This hypothesis may explain a large portion of the ecosystem responses during the LGM, but does not account for all observed changes. Paucity of site reconstructions (e.g. in the Amazon basin), and lack of quantitative paleoclimatic responses derived from proxies to environmental conditions could partly explain the observed discrepancies. Regional responses of mosaic environmental ecosystems to a generally cooler temperature could be involved, without any need to invoke precessionnal and extra-tropical influences.
Plan de classement
Analyse, évolution des climats [021CLIMAT01]
;
Evaluation et gestion des ressources en eau [062EVAEAU]
;
Géologie du quaternaire [064GEOQUA]
Description Géographique
VENEZUELA ; COLOMBIE ; EQUATEUR ; PEROU ; BOLIVIE ; CHILI ; ARGENTINE ; ANDES ; AMERIQUE DU SUD
