Interactions végétation-climat au cours des derniers 425.000 ans en Europe occidentale. Le message du pollen des archives marines

• Published in: Quaternaire
• Main Author: Sánchez Goňi, María Fernanda
• Format: Article in Journal/Newspaper
• Language: French
• Published: Association française pour l’étude du quaternaire 2009
• Subjects: dernière entrée en glaciation; Eémien; Europe occidentale; événements d’Heinrich; Holocène; interactions végétation-climat; interglaciaires passés; oscillations de Dangard-Oeschger; séquences polliniques marines; stade isotopique 11; stade isotopique 5; variabilité climatique millénaire; Dansgaard-Oeschger oscillations; Eemian; Heinrich events; isotopic stage 11; isotopic stage 5; last glacial inception; marine pollen sequences; Millennial-scale climatic variability; past interglacials; vegetation-climate relationships; western Europe; geo; hist; Tundra
• Online Access: http://journals.openedition.org/quaternaire/585

Pollen from marine archives off western Iberia has been proved to be a particularly useful tool for precise reconstruction of the impact of climatic changes at orbital and millennial time scales, Heinrich events and Dansgaard-Oeschger (D-O) oscillations, on the continental biosphere over the last 140,000 years. The direct correlation between pollen, marine climatic and ice volume proxies from these sequences allows us to demonstrate the synchronicity between sea surface temperature changes in the mid-latitudes of the north-eastern Atlantic Ocean and the vegetation response of Iberia. There is, therefore, a dynamic equilibrium between vegetation and climate for short periods of forcing. This work also shows that the impact of the D-O oscillations in Europe was spatially variable. South-western Iberian ecosystems, alternating between semi-desert landscapes (D-O stadials) and open Mediterranean forest (D-O interstadials) were particularly affected by this millennial-scale climatic variability while in northernmost regions the response of the temperate forest was almost muted. Hence, pine forest developed following the D-O warming oscillations. In addition, a time-lag between ice volume variations in the northern hemisphere and forest cover changes in south-western Europe has been recorded during marine isotopic stage 5e (MIS 5e). The ice volume minimum is reached at 128 ka, 2,000 years earlier than the main forest expansion defining the onset of the Eemian at 126 ka; the substantial growth of the ice caps occurred at 115 ka while the forest survived in Iberia up to 110 ka. The forest succession detected at different latitudes during the last interglacial shows that the Iberian Eemian lasted 16,000 years and, therefore, 5,000 years more than the Eemian in northernmost regions above 50°N (11,000 years). This study also suggests a first southward displacement of the Boreal tree-line between 122 ka and 120 ka which would imply tundra expansion. This displacement of the vegetation belts precedes the substantial ...