Climate Variability in the North-Western Iberian Peninsula During the Last Deglaciation.

Vegetation reconstruction from north-western Portugal estuarine cores reflects millennial- to centennial-scale climate variability during the Last -Glacial–Interglacial Transition (LGIT) in the Douro basin. These vegetation cover changes match perfectly the climatic pattern detected in the North Atlantic region and in Greenland. Changes between high and weak forested phases in the Douro basin are associated with warm and cold episodes, respectively. The first warm episode, the Bölling, occurring within the LGIT, follows the Oldest Dryas episode (terrestrial equivalent of the marine Heinrich 1 event) and was characterised by the expansion of pine, oak and birch. Subsequently, a rapid climate reversal was revealed by the contraction of that arboreal association and increase of herbaceous taxa probably reflecting the centennial-scale Older Dryas episode (one of the well-known Intra Bölling-Allerød cold events). The Allerød event, representing the subsequent warming phase, was characterised by the expansion of alder -followed by pine. Afterwards, an abrupt cooling occurred, evidenced by the replacement of temperate trees (pine and oak) by herbaceous plants (compositae and grasses), reflecting the Younger Dryas cold event. Finally, the end of the LGIT was characterised by a maximal expansion of temperate and humid forest (birch, oak, pine, ashes, alder), as likely being the result of the climate improvement that characterises the present-day interglacial, the Holocene. [ABSTRACT FROM AUTHOR]