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The Last Interglacial climatic optimum, ca. 128 ka, is the most recent climate interval significantly warmer than present, providing an analogue (albeit imperfect) for ongoing global warming and the effects of Greenland Ice Sheet (GIS) melting on climate over the coming millennium. While some climate models predict an Atlantic meridional overturning circulation (AMOC) strengthening in response to GIS melting, others simulate weakening, leading to cooling in Europe. Here, we present evidence from new proxy-based paleoclimate and ocean circulation reconstructions that show that the strongest warming in western Europe coincided with maximum GIS meltwater runoff and a weaker AMOC early in the Last Interglacial. By performing a series of climate model sensitivity experiments, including enhanced GIS melting, we were able to simulate this configuration of the Last Interglacial climate system and infer information on AMOC slowdown and related climate effects. These experiments suggest that GIS melt inhibited deep convection off the southern coast of Greenland, cooling local climate and reducing AMOC by ~24% of its present strength. However, GIS melt did not perturb overturning in the Nordic Seas, leaving heat transport to, and thereby temperatures in, Europe unaffected. [ABSTRACT FROM AUTHOR]

Holocene changes are recorded by sedimentology and palynology on a 20 m long core retrieved in the mouth of the Douro estuary (northwestern Portugal). Results show that the early Holocene (10720-6530 calibrated/call YBP) was characterized by a warm and humid climate as testified by a well-established Pinus-Quercus-Alnus regional forest. Shelf and slope foraminifera assemblages as well as echinoderms gradually increased toward the end of this period, reflecting the sea-level rise that occurred between 11500 and 6000 cal yr BP. A gravel barrier developed in the southern part of the estuary as a result of sea-level rise attenuation and strong hydrodynamism of the river. A radical change from regional fluvially transported pollen assemblages (mainly composed of trees) to pollen spectra derived from local vegetation (mainly Ericaceae and Poaceae) occurred between 6530 and 1500 col yr BP, contemporaneously to the settlement of the gravel barrier. This suggests that the northward migration of the river main channel, already testified by the existence of a palaeovalley with its axis located southward of the present main channel, occurred as early as 6530 cal yr BP. [ABSTRACT FROM AUTHOR]