Holocene palaeohydrological changes in the northern Mediterranean borderlands as reflected by the lake-level record of lake ledro, northeastern Italy

Abstract

A lake-level record of Lake Ledro (northern Italy) spans the entire Holocene with a chronology derived from 51 radiocarbon dates. It is based on a specific sedimentological approach that combines data from five sediment profiles sampled in distinct locations in the littoral zone. On a millennial scale, the lake-level record shows two successive periods from 11,700 to 4500 cal yr BP and from 4500 cal yr BP to the present, characterized by lower and higher average lake levels, respectively. In addition to key seasonal and inter-hemispherical changes in insolation, the major hydrological change around 4500 cal yr BP may be related to a non-linear response of the climate system to orbitally-driven gradual decrease in insolation. The Ledro record questions the notion of an accentuated summer rain regime in the northern Mediterranean borderlands during the boreal insolation maximum. Moreover, the Ledro record highlights that the Holocene was punctuated by successive centennial-scale highstands. Correlations with the Preboreal oscillation and the 8.2 ka event, and comparison with the atmospheric 14 C residual record, suggest that short-lived lake-level fluctuations developed at Ledro in response to (1) final steps of the deglaciation in the North Atlantic area and (2) variations in solar activity.

Contrasting patterns of climatic changes during the Holocene across the Italian Peninsula reconstructed from pollen data

“…Others cores have been obtained from other locations within Lake Ledro (Ledro I, Ledro II and Ponale: Magny et al, 2012a), but only the profundal LL081 is used in this study. The chronology spans the last 17 000 yr Grosseto (7 m asl) using 13 14 C dates (Table 1) and 1 date from the Ledro II littoral site (Magny et al, 2012a) aligned using stratigraphic comparison. The temporal resolution is approximately estimated to 66 yr / sample throughout the Holocene (more details are given in Joannin et al, 2013).…”

“…This accelerates during the late Holocene (from 4100 cal yr BP onwards) through continuous records of anthropogenic pollen indicators and drops in arboreal pollen percentages. More details on the Lake Ledro pollen, vegetation and lake-level history are given in Joannin et al (2013) and in Magny et al (2009Magny et al ( , 2012a.…”

“…Magri and Sadori, 1999;Allen et al, 2002;Sadori et al, 2004Sadori et al, , 2011Zanchetta et al, 2007a, b;Colonese et al, 2011;Finne et al, 2011;Giraudi et al, 2011;Zhornyak et al, 2011;Magny et al, 2009Magny et al, , 2011Magny et al, , 2012aDi Rita et al, 2013;Calo et al, 2012). These data show a complex pattern of climatic change across the Mediterranean during the Holocene, with strong spatial and temporal variability (e.g.…”

Holocene climate change, permafrost and cryogenic carbonate formation: insights from a recently deglaciated, high-elevation cave in the Austrian Alps

“…At the same time the Upper Grindelwald Glacier advanced as shown by speleothem data in the adjacent Milchbach Cave (Luetscher et al, 2011). High lake levels recorded in the Jura Mountains (Magny, 2004) and at Lago di Ledro in the Southern Alps (Magny et al, 2012) suggest a cool and wet climate during the middle of the first millennium BC. One sample of MSK Cave yielded a significantly younger date which suggests calcite precipitation ca.…”

Quaternary climate change and Heinrich events in the southern Balkans: Lake Prespa diatom palaeolimnology from the last interglacial to present

“…Quaternary researchers in the last few decades have made considerable efforts to understand spatial climate variability in the Mediterranean, but the main underlying mechanisms are still under debate (Magny et al 2012). This is partly because of gaps in our understanding of spatial and temporal variability.…”