Climatic Reconstruction in Europe for 18,000 YR B.P. from Pollen Data

Abstract

An improved concept of the best analogs method is used to reconstruct the climate of the last glacial maximum from pollen data in Europe. In order to deal with the lack of perfect analogs of fossil assemblages and therefore to obtain a more accurate climate reconstruction, we used a combination of pollen types grouped according to plant phenology and present climate constraints rather than pollen percentages for each individual taxon. The distribution of pollen taxa into plant functional types (PFTs) is aimed to reflect the vegetation in terms of biomes which have a wider distribution than a species. The climatic variables are then calibrated on these PFTs using an artificial neural network technique. The use of PFTs allowed us to deal with situations where pollen assemblages have only partial modern analogs. The method is applied to the glacial steppic vegetation in Europe, using 15 pollen records. North of the Pyrenees–Alps line, the reconstructed temperatures were lower than today: −30 ± 10°C for the temperature of the coldest month ( Tc) and −12 ± 3°C for the annual mean ( Tann). South of that line, Tc and Tann anomalies were respectively, −15 ± 5°C and −10 ± 5°C. The available moisture index and annual precipitation were also lower than present: −60 ± 20% north of Mediterranean Sea, (−800 ± 100 mm for precipitation). In Italy and Greece, the available moisture was 20% lower, with a precipitation anomaly of ca. −600 ± 200 mm. Southward, the moisture index was close to that at present (±20%), and precipitation was lower (−300 ± 300 mm).

Increased seasonality in the Western Mediterranean during the last glacial from limpet shell geochemistry

“…LGM air temperatures reconstructed using pollen records on the coast of the Alboran Sea, indicate a cooling of 9°C in annual air temperatures but a much greater cooling of 15°C in the air temperature of the coldest month (Peyron et al, 1998).…”

Environmental and climatic changes in the Jura mountains (eastern France) during the Lateglacial–Holocene transition: a multi-proxy record from Lake Lautrey

“…The plant functional types (PFTs) method is a transfer function in which pollen percentages are first transformed into PFT scores (Peyron et al, 1998). PFTs are broad classes of plants defined by their structural and functional features (Prentice et al, 1996).…”

“…The modern pollen data set used in the quantitative reconstructions includes 868 surface pollen samples from Eurasia including the Mediterranean basin, Pyrenees, Scandes Mountains, Kazakhstan and the Tibetan plateau (Peyron et al, 1998) to get samples more representative of some specific past vegetation types. Table 3 presents the correlation coefficients between observed and reconstructed values of climate parameters.…”

“…On the basis of modern pollen data set coupled with known climatic conditions, the climatic parameters (i.e. the mean temperature of the warmest month, the annual precipitation and the ratio of real to potential evapotranspiration: E/PET) have been calculated using an artificial neural network calibration Peyron et al, 1998). The validation tests ( Table 3) may suggest that the BAM reconstructions are more accurate than the PFT method.…”

High magnitude and rapid incision from river capture: Rhine River, Switzerland

“…Climate was generally drier during glacial periods, potentially with up to 60% less precipitation [Peyron et al, 1998], thus our calculated response times based on modern climate are likely minima. Changes in grain size during glacial times are not constrained along the Rhine River.…”