Climate-driven changes in lake conditions during late MIS 3 and MIS 2: a high-resolution geochemical record from Les Echets, France

International audience ; Ice-core (Dansgaard et al. 1993; Johnsen et al. 2001; NGRIP members 2004) and marine sediment records (Bond et al. 1992; Moreno et al. 2004; Rasmussen & Thomsen 2004) spanning the last glacial cycle provide compelling evidence of multiple reorganizations of the climatic system triggered by changes thought to originate in the North Atlantic region (Broecker et al. 1992; Clark et al. 2002). Sudden shifts in air temperature from a cool climate to interstadial values, known as Dansgaard-Oeschger events (DO), have been active most notably during Marine Isotope Stage (MIS) 3. Abrupt and large in amplitude, DO cycles operated on a millennial to centennial time scale and are best expressed in the North Atlantic region (Dansgaard et al. 1993; Allen et al. 1999; NGRIP members 2004; Moreno et al. 2005; Grimm et al. 2006; Wohlfarth et al. 2008), though recent research suggests that these events were probably important on a global scale (e.g. Voelker et al. 2002). Iceberg surges, known as Heinrich events (H events), appear in marine records as sudden cold spells associated with a drastic reduction in sea surface temperature, a southern shift of the Polar Front, disruption of North Atlantic thermohaline circulation and substantial delivery of ice-borne detritus to the open ocean, reaching as far south as Portugal (Bond et al. 1992; Broecker et al. 1992; Bard et al. 2000; Hemming 2004). On the European mainland, lake sediments are the most promising archives for recording long-term and short-term climatic changes (Voelker et al. 2002). The few long lacustrine records from continental Europe show that, on a broad scale, long-term palaeoclimate variations are expressed clearly through changes in vegetation composition and dynamics (Woillard & Mook 1982; de Beaulieu & Reille 1984; Guiot et al. 1989; Allen & Huntley 2000; de Beaulieu et al. 2001; Guiter et al. 2003). However, in the context of abrupt climate change (e.g. for most of MIS 3), only limited palaeoecological information is ...