North–South Palaeohydrological Contrasts in the Central Mediterranean During the Holocene: Tentative Synthesis and Working
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EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Open Access Biogeosciences Biogeosciences Discussions Open Access Open Access Clim. Past, 9, 2043–2071, 2013 Climate www.clim-past.net/9/2043/2013/ Climate doi:10.5194/cp-9-2043-2013 of the Past of the Past © Author(s) 2013. CC Attribution 3.0 License. Discussions Open Access Open Access Earth System Earth System Dynamics Dynamics Discussions North–south palaeohydrological contrasts in the central Open Access Open Access Mediterranean during the Holocene: tentative synthesisGeoscientific and Geoscientific Instrumentation Instrumentation working hypotheses Methods and Methods and Data Systems Data Systems M. Magny1, N. Combourieu-Nebout2, J. L. de Beaulieu3, V. Bout-Roumazeilles4, D. Colombaroli5, S. Desprat6, 7 8,1 1 1 9 10 11 2 5 Discussions Open Access A. Francke , S. Joannin , E. Ortu , O. Peyron , M. Revel , L. Sadori , G. Siani , M. A. Sicre , S. SamartinOpen Access , A. Simonneau12, W. Tinner5, B. Vanniere` 1, B. Wagner7, G. Zanchetta13, F. Anselmetti14,*, E. Brugiapaglia15, Geoscientific 12 16 12,17 1 18 19 Geoscientific20 21 22 E. Chapron , M. Debret , M. Desmet , J. Didier , L. Essallami , D. Galop , A. Gilli , J. N. Haas , N. Kallel , Model Development L. Millet1, A. Stock1, J. L. Turon6, and S. Wirth20 Model Development Discussions 1CNRS-UMR6249, Laboratoire Chrono-Environnement, UFR des Sciences et Techniques, 16 Route de Gray, 25030 Besanc¸on, France Open Access 2 Open Access CNRS-UMR8212, Laboratoire des Sciences du Climate et de l’Environnement (LSCE)-Gif-sur-Yvette, France Hydrology and 3CNRS-UMR7263-IMBE, Universite´ Paul Cezanne,´ Aix-en-Provence, France Hydrology and 4CNRS-UMR8217, Geosyst´ emes,` Universite´ de Lille 1, 59655, Villeneuve d’Ascq, FranceEarth System Earth System 5 Oeschger Center for Climate Change Research and Insitute of Plant Sciences, University of Bern,Sciences Altenbergrain 21, Sciences 3013 Bern, Switzerland 6CNRS-UMR5808-Ecole Pratique des Hautes Etudes, Environnements et Paleoenviuronements´ Oceaniques,´ Discussions Open Access Universite´ de Bordeaux 1, 33405 Talence, France Open Access 7University of Cologne, Institute for Geology and Mineralogy, Cologne, Germany Ocean Science 8CNRS-USR3124 Maison des Sciences de l’Homme et de l’Environnement (MSHE) Ledoux,Ocean Besanc¸on, Science France Discussions 9Geosciences´ Azur, Observatoire Oceanologique,´ La Darse, BP 48, 06235 Villefranche/Mer, France 10Dipartimento di Biologia Ambientale, Universita` di Roma “La Sapienza”, Piazzale Aldo Moro 5, 00185 Roma, Italy 11CNRS-UMR8148 IDES, Departement´ des Sciences de la Terre, Universite´ Paris Sud, 91405 Orsay, France Open Access Open Access 12CNRS-UMR7327 ISTO, Universite´ d’Orleans,´ BRGM, 1A Rue de la Ferollerie,´ 45071 Orleans,´ France 13Dipartimento di Scienze della Terra, Via S. Maria 53, 56126 Pisa, Italy Solid Earth 14 ¨ Solid Earth Eawag, Department of Surface Waters, Uberlandstrasse 133, 8600 Dubendorf,¨ Switzerland Discussions 15Dipartimento di Scienze Animali, Vegetali e dell’Ambiente, Universita` degli Studi del Molise, Campobasso, Italy 16CNRS-UMR 6143 M2C, Universites´ de Caen Basse-Normandie et Rouen, 14000 Caen, France 17 GeoHydrosyst´ emes` Continentaux, EA6293, Universite´ F. Rabelais de Tours, Departement´ Geosciences-Environnement,´ Open Access Open Access Faculte´ des Sciences et Techniques, Parc de Grandmont, 37200 Tours, France 18Universite´ de Gabes,` Faculte´ des Sciences de Gabes,` Gabes,` Tunisia The Cryosphere 19 The Cryosphere CNRS-UMR5602 GEODE, Maison de la Recherche de l’Universite´ du Mirail, Toulouse, France Discussions 20Geological Institute, ETH Zurich,¨ Zurich,¨ Switzerland 21Insitut fur¨ Botanik, Universitat¨ Innsbruck, Innsbruck, Austria 22Faculte´ des Sciences de Sfax, Unite´ GEOGLOB, Route de Soukra, BP 802, 3038 Sfax, Tunisia *current address: Insitute of Geological Sciences, University of Bern, Baltzerstrasse 1–3, 3012 Bern, Switzerland Correspondence to: M. Magny ([email protected]) Received: 26 March 2013 – Published in Clim. Past Discuss.: 5 April 2013 Revised: 21 June 2013 – Accepted: 22 July 2013 – Published: 2 September 2013 Published by Copernicus Publications on behalf of the European Geosciences Union. 2044 M. Magny et al.: North–south palaeohydrological contrasts in the central Mediterranean Abstract. On the basis of a multi-proxy approach and a strat- and decreases in solar activity during the interval 11 700– egy combining lacustrine and marine records along a north– 7000 cal BP, and to a possible combination of NAO-type cir- south transect, data collected in the central Mediterranean culation and solar forcing since ca. 7000 cal BP onwards. within the framework of a collaborative project have led to Thus, regarding the centennial-scale climatic oscillations, the reconstruction of high-resolution and well-dated palaeohy- Mediterranean Basin appears to have been strongly linked to drological records and to assessment of their spatial and tem- the North Atlantic area and affected by solar activity over the poral coherency. Contrasting patterns of palaeohydrological entire Holocene. changes have been evidenced in the central Mediterranean: In addition to model experiments, a better understand- south (north) of around 40◦ N of latitude, the middle part of ing of forcing factors and past atmospheric circulation pat- the Holocene was characterised by lake-level maxima (min- terns behind the Holocene palaeohydrological changes in the ima), during an interval dated to ca. 10 300–4500 cal BP to Mediterranean area will require further investigation to es- the south and 9000–4500 cal BP to the north. Available data tablish additional high-resolution and well-dated records in suggest that these contrasting palaeohydrological patterns selected locations around the Mediterranean Basin and in ad- operated throughout the Holocene, both on millennial and jacent regions. Special attention should be paid to greater centennial scales. Regarding precipitation seasonality, maxi- precision in the reconstruction, on millennial and centen- mum humidity in the central Mediterranean during the mid- nial timescales, of changes in the latitudinal location of the dle part of the Holocene was characterised by humid win- limit between the northern and southern palaeohydrological ters and dry summers north of ca. 40◦ N, and humid win- Mediterranean sectors, depending on (1) the intensity and/or ters and summers south of ca. 40◦ N. This may explain an characteristics of climatic periods/oscillations (e.g. Holocene apparent conflict between palaeoclimatic records depending thermal maximum versus Neoglacial, as well as, for instance, on the proxies used for reconstruction as well as the syn- the 8.2 ka event versus the 4 ka event or the Little Ice Age); chronous expansion of tree species taxa with contrasting cli- and (2) on varying geographical conditions from the west- matic requirements. In addition, south of ca. 40◦ N, the first ern to the eastern Mediterranean areas (longitudinal gradi- millennium of the Holocene was characterised by very dry ents). Finally, on the basis of projects using strategically lo- climatic conditions not only in the eastern, but also in the cated study sites, there is a need to explore possible influ- central- and the western Mediterranean zones as reflected by ences of other general atmospheric circulation patterns than low lake levels and delayed reforestation. These results sug- NAO, such as the East Atlantic–West Russian or North Sea– gest that, in addition to the influence of the Nile discharge Caspian patterns, in explaining the apparent complexity of reinforced by the African monsoon, the deposition of Sapro- palaeoclimatic (palaeohydrological) Holocene records from pel 1 has been favoured (1) by an increase in winter precipi- the Mediterranean area. tation in the northern Mediterranean borderlands, and (2) by an increase in winter and summer precipitation in the south- ern Mediterranean area. The climate reversal following the 1 Introduction Holocene climate optimum appears to have been punctuated by two major climate changes around 7500 and 4500 cal BP. At the interface between the European temperate and the In the central Mediterranean, the Holocene palaeohydro- African tropical zones, the Mediterranean area appears to be logical changes developed in response to a combination very sensitive to even low-amplitude variations in the hydro- of orbital, ice-sheet and solar forcing factors. The maxi- logical cycle. This transitional zone is influenced by tropi- mum humidity interval in the south-central Mediterranean cal circulation cells within the subtropical anticyclone belt started ca. 10 300 cal BP, in correlation with the decline and associated aridity, as well as by the mid-latitude west- (1) of the possible blocking effects of the North Atlantic erlies and cyclogenesis (Tzedakis et al., 2009). This results anticyclone linked to maximum insolation, and/or (2) of in a marked precipitation seasonality that is crucial for both the influence of the remnant ice sheets and fresh water Mediterranean ecosystems and societies. Climate change forcing in the