Vegetation and Climate in the Pyrenean Mountains (southern France) during the Last 15000 Years Bp: a Pollen-Inferred Quantitative Reconstruction

Climatic linkages between the North Atlantic and west Europe areas have been investigated for the last 15,000 yrs from four high-temporal pollen records located in the western Pyrenees Mountains. Mountain areas are of particular interest because the vegetation is very sensitive to variations in climate and human impact, and also because the vegetation responses to climatic changes are more pronounced at higher altitudes than in the lowlands, and are well recorded in pollen sequences. In the Alps Mountains, the lateglacial and Holocene climate variations are now well known from numerous multi-proxies approaches. However no climate estimates are available in the Pyrenean Mountains (southern France). This study aim to test the sensitivity of the Pyrenean Mountains area to even short term and relatively weak climatic fluctuations recognised in the North Atlantic region. Here, we reconstruct the vegetation and the climate changes along an latitudinal/altitudinal gradient in the western part of the Pyrenees for the last 15,000 yrs BP from 4 high-resolution pollen records located from the oceanic shore to the central Pyrenees with a chronology established on 40 radiocarbon dates : from west to east, the Mouriscot lake record located near the ocean coast at 50m asl (43.45 N/1.55W), the Occabe record in Basque mountains located in the Iraty massif at 1300m (43.03N/1.10W); the Piet record at 1150m in the Ossau valley (42.88N/0.42W) and the Ech record located at lower altitude (600m) in the Lourdes basin (43.7N/0.08W) in the central part of the chain. From the 4 cores, the modern analogues technique has been used to obtain robust and precise quantitative estimates of the annual temperature, the mean temperature of the warmest/coldest month, total annual precipitation, and the ratio of real to potential evapotranspiration. Pollen-inferred climate estimates show that cold and dry conditions prevailed during the Oldest and Younger Dryas while temperate conditions are evidenced during the Lateglacial interstadial and the Holocene. Several cool short-lived events (Older Dryas, Gerzensee/Preboreal Oscillations, 8.2ka) indicate that the climate oscillations associated with the successive steps of the deglaciation in North Atlantic have also been observed in the western Pyrenean areas. This confirms strong climatic linkages between the North Atlantic and west Europe, particularly the western Pyrenees Mountains.