Vegetation and climate of chilean Patagonia during the last 20, 000 years from marine pollen data
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...
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Other Authors: | , , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
Published: |
HAL CCSD
2011
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Subjects: | |
Online Access: | https://theses.hal.science/tel-00659194 https://theses.hal.science/tel-00659194/document https://theses.hal.science/tel-00659194/file/VA2_Montade_Vincent_1212011.pdf |
Summary: | 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 ... |
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