Vegetation and climate of chilean Patagonia during the last 20, 000 years from marine pollen data

• Main Author: Montade, Vincent
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Paris Sud - Paris XI, Universidad austral de Chile, Nathalie Combourieu-Nebout
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2011
• Subjects: South hemisphere; South America; Chile; Patagonia; Deglaciation; Holocene; Paleoenvironment; Climate; Westerlies; Vegetation; Pollen; Marine palynology; Oceanic core; Carotte marine; Palynologie marine; Végétation; Vents d’ouest; Paléoenvironnement; Holocène; Déglaciation; Patagonie; Chili; Amérique du Sud; Hémisphère Sud; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarctic; The Antarctic; Antarc*
• Online Access: https://tel.archives-ouvertes.fr/tel-00659194; https://tel.archives-ouvertes.fr/tel-00659194/document; https://tel.archives-ouvertes.fr/tel-00659194/file/VA2_Montade_Vincent_1212011.pdf

In the context of global warming, paleoclimate records at different time and spatial scales appear critical to understand climate mechanisms. Chilean Patagonia (41°S to 56°S), crossed by the Andes from north to south, represents a major topographic constraint on ocean and atmospheric circulation. It is the only region that intercepts the entire southern westerly wind belt. Thus it represents a key-area for the study of paleoenvironmental changes in the southern hemisphere and the understanding of ocean-atmosphere mechanisms and their interactions from the mid- to high-latitudes of the southern hemisphere. In this context, the purposes are: (1) to test the pollen analysis on marine surface sediments in this region, (2) to study the continental changes of paleoenvironments during the last 20,000 years from two oceanic cores of the "PACHIDERME" campaign (MD07-3088 and MD07-3104) and (3) to evaluate their links with southern westerly wind belt activity and with the influence of these winds on the southern hemisphere and with the climate at a global scale. The pollen analyses of marine surface sediments in fjords or offshore from Chilean Patagonia reflect the present-day vegetation from the nearby continental area. At the Peninsula of Taitao (46°S), the North Patagonian forest expansion after 17.6 kyr shows the beginning of the deglaciation. This last (period) is interrupted by a wet and cool event, the Antarctic Cold Reversal (ACR), that was expressed here by development of the Magellanic moorland linked to the southern westerly wind intensification. The expansion of heliophytic taxa at ~11 kyr illustrates the beginning of the Holocene under warmer and drier conditions that are also recorded around the fjord of Reloncavi (41°S). These conditions persisted until ~8-7 kyr, and then the vegetation changes during the Holocene show a larger climate variability toward a cooler and wetter climate that enhances in northern Patagonia later ~6-5 kyr during the Late Holocene. Our results compared with the regional ...