Timing of glaciation in the Mediterranean mountains during the last cold stage

Abstract

Recent research in the mountains of the Mediterranean has attempted to establish the timing of the maximum extent of glaciers during the last cold stage. Several dating methods have been utilised and new dating frameworks have emerged in key areas. In several places, multiple dating techniques (radiocarbon, optically stimulated luminescence, U-series) applied to glacial and associated sediments suggest that local glacier maxima preceded the global Last Glacial Maximum (LGM, ca. 18 14 C ka BP/ 21 cal. ka BP) by at least several thousand years. Studies in Spain, the Pyrenees, the Maritime Alps and Turkey utilising cosmogenic isotope analyses ( 10 Be and 36 Cl), have yielded glacial geochronologies with maxima that correlate closely with the marine isotope record of ice volume and the global LGM. In some cases, the use of different geochronological techniques has led to conflicting evidence for the timing of the local last glacier maxima in the same area. From a palaeoclimate perspective, glacier-climate reconstructions for the local last glacier maxima in the mountains of central Italy, northern Greece and western Turkey indicate that climate was wet and cold. In Italy and Greece the local glacier maxima preceded the driest part of the last cold stage -as indicated by palaeoecological records -by several thousand years. For western Turkey, however, recent cosmogenic exposure ages combined with glacier modelling suggest a local last glacier maximum characterised by cold and wet conditions coinciding with the global LGM. The available evidence indicates that a dichotomy is emerging, not only in our understanding of the timing of glaciation across the Mediterranean, but also in the palaeoclimatic interpretations derived from glacial and palaeoecological records.

Timing and nature of late Quaternary mountain glaciation

“…Other chronologies, based primarily on 10 Be dating of moraine boulder exposure ages from the Pyrenees and Kaçkar mountains, however, suggest a close correlation of local mountain glacier maxima with the global LGM. Hughes and Woodward (2008) suggest the early local mountain glacier maximum is consistent with long palaeoecological records from the region, with the rapid ice build-up characteristic of the small mountain glaciers, and with models of southward diverted cyclonic tracks. They further infer that the global LGM-correlative chronologies are problematic because the global LGM was very dry in the region, and extreme temperature depression would have been required to drive glacier growth at that time.…”

“…Ice retreated rapidly from those maximum positions, with 80% of ice volume lost by 18 ka, and readvanced during two Lateglacial stades. Hughes and Woodward's (2008) study of the Mediterranean region demonstrates that Late Pleistocene glacial maxima several thousand years prior to the global LGM. Other chronologies, based primarily on 10 Be dating of moraine boulder exposure ages from the Pyrenees and Kaçkar mountains, however, suggest a close correlation of local mountain glacier maxima with the global LGM.…”

Reconstructing glacier-based climates of LGM Europe and Russia – Part 3: Comparison with previous climate reconstructions

“…However, it is not considered the principal cause of the discrepancy for two reasons. First, recent studies dating glacial-geological evidence (e.g Sanchez and Arquer, 2002;García-Ruiz et al, 2003;Woodward et al, 2004;Hughes and Woodward, 2008) propose changes to the extent of LGM glaciers rather than concluding the region was not glaciated. For example, the chronology of the Lourdes Valley, Northern Pyrenees established by Herail et al (1986) places the terminus of the LGM glacier 10 km to 15 km behind the terminus of the maximum glacial advance.…”

Short-term signals of climate change in Italian summit vegetation: observations at two GLORIA sites

“…Europe shows a general north-south gradient of mountain endemism, increasing from boreal and temperate mountains to the Mediterranean summits (Faverger 1972). Many authors postulate that such gradient on endemic richness existed because, during the Pleistocene, mountains of the Mediterranean region were only partly glaciated and remained more isolated than northern European ones, which were extensively ice-covered and whose margins were more connected to surrounding areas (Hughes & Woodward 2008). The isolation in Mediterranean high mountain environments, caused by the orographic discontinuity of cold areas (Chapin & Körner 1994;Körner 2003), gave rise to a peak of cryophilic endemic plants (Catonica & Manzi 2002).…”