North–south palaeohydrological contrasts in the central Mediterranean during the Holocene: tentative synthesis and working hypotheses

Abstract

On the basis of a multi-proxy approach and a strategy combining lacustrine and marine records along a north–south transect, data collected in the Central Mediterranean within the framework of a collaborative project have led to reconstruction of high-resolution and well-dated palaeohydrological records and to assessment of their spatial and temporal coherency. Contrasting patterns of palaeohydrological changes have been evidenced in the Central Mediterranean: south (north) of around 40&deg; N of latitude, the middle part of the Holocene was characterised by lake-level maxima (minima), during an interval dated to ca. 10 300–4500 cal BP to the south and 9000–4500 cal BP to the north. Available data suggest that these contrasting palaeohydrological patterns operated throughout the Holocene, both on millennial and centennial scales. Regarding precipitation seasonality, maximum humidity in the Central Mediterranean during the middle part of the Holocene was characterised by humid winters and dry summers north of ca. 40&deg; N, and humid winters and summers south of ca. 40&deg; N. This may explain an apparent conflict between palaeoclimatic records depending on the proxies used for reconstruction as well as the synchronous expansion of tree species taxa with contrasting climatic requirements. In addition, south of ca. 40&deg; N, the first millennium of the Holocene was characterised by very dry climatic conditions not only in the Eastern, but also in the Central and the Western Mediterranean zones as reflected by low lake levels and delayed reforestation. These results suggest that, in addition to the influence of the Nile discharge reinforced by the African monsoon, the deposition of Sapropel 1 has been favoured (1) by an increase in winter precipitation in the northern Mediterranean borderlands, and (2) by an increase in winter and summer precipitation in the southern Mediterranean area. The climate reversal following the Holocene climate optimum appears to have been punctuated by two major climate changes around 7500 and 4500 cal BP. <br><br> In the Central Mediterranean, the Holocene palaeohydrological changes developed in response to a combination of orbital, ice-sheet and solar forcing factors. The maximum humidity interval in the south-central Mediterranean started at ca. 10 300 cal BP, in correlation with the decline (1) of the possible blocking effects of the North Atlantic anticyclone linked to maximum insolation, and/or (2) of the influence of the remnant ice sheets and fresh water forcing in the North Atlantic Ocean. In the north-central Mediterranean, the lake-level minimum interval began only around 9000 cal BP when the Fennoscandian ice-sheet disappeared and a prevailing positive NAO-type circulation developed in the North Atlantic area. The major palaeohydrological oscillation around 4500–4000 cal BP may be a non-linear response to the gradual decrease, with additional key seasonal and interhemispherical changes, in insolation. On a centennial scale, the suc...

The last 7 millennia of vegetation and climate changes at Lago di Pergusa (central Sicily, Italy)

“…Besides, they underline an important spatial variability of landscapes and local responses to climate changes (de Beaulieu et al, 2005;Carrión et al, 2010a, b;Magny et al, 2012Magny et al, , 2013. In this context, understanding responses to climate changes in Sicily, the largest Mediterranean island, is particularly interesting, as its central geographic position in the Mediterranean Basin makes it a key region for the understanding of Holocene climates and environments.…”

French Alpine Foreland Holocene Paleoseismicity Revealed by Coeval Mass Wasting Deposits in Glacial Lakes

“…Similarly, a regional earthquake at ca. 9550 cal BP occurring during the Boreal period that was associated with important environmental changes (in vegetation, glacier activity and lake-level) in Western Europe (Magny et al 2014), may have triggered MWD1 in Lake Paladru, SE1 in Lake Blanc Huez and the HDU in Lake Le Bourget. The larger amplitude of the coeval HDU event is here clearly resulting from its isolation from the Rhone River and a drastic drop in siliciclastic sediment supply.…”

Climate, palaeohydrology and land use change in the Central Iberian Range over the last 1.6 kyr: The La Parra Lake record

“…between the western and eastern Mediterranean, Roberts et al, 2012). A number of climate reconstructions over the last two millennia for the Mediterranean region have been recently published (see Valero-Garcés and Moreno, 2011;Moreno et al, 2012;Lionello, 2012;Roberts et al, 2012, Magny et al, 2013 which describe rapid environmental and climatic changes coinciding chronologically with the MCA and the LIA with underlying regional trends. These trends highlight timing discrepancies in palaeohydrological shifts, with associated variability in inferences concerning the definition of age ranges for wet and dry phases.…”