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The Little Ice Age (LIA) is a well-recognized climatic event during which the glaciers in the Alps advanced and reached their maximum Holocene extent. During their retreat following the LIA, the glaciers left large areas of loose or poorly consolidated glacial deposits in their forelands, which are subject to paraglacial reworking and may represent potential hazards for human infrastructures. In this study, we present a regional scale mapping of the LIA and post-LIA glacial deposits and a reconstruction of the maximum LIA extents of glaciers in the same area. This work is motivated by a local law requiring the classification of areas subject to natural hazards in Trentino (Italian Alps). Results highlight that glaciers shrunk by 63% from the LIA maximum, leaving 30 km 2 of unconsolidated deposits, which are subject to geomorphic paraglacial processes. Potentially hazardous consequences can occur, in particular, during high-magnitude instantaneous events, causing debris and mud flows, mass wasting from debris-covered ice, and floods from small moraine-dammed lakes. [ABSTRACT FROM AUTHOR]

A pronounced climate reorganization characterized the Lateglacial-Holocene transition in the Northern Hemisphere. Glaciers in the Alps reacted to the last climate deterioration at the end of the Late Pleistocene leaving landscape features suitable for reconstructing Lateglacial and early Holocene history. In this context, the Upper Peio Valley in the Ortles-Cevedale Group (Rhaetian Alps, Italy) has well-preserved moraines of La Mare Glacier and Careser Glacier, which we used to reconstruct the glaciers' behaviour and to investigate the Lateglacial-Holocene transition. Detailed glacier reconstructions combined with 11 new 10Be exposure ages allow dating of the response of these glaciers to the Younger Dryas ( YD) cold event. La Mare and Careser glaciers reacted to the YD with a double response, building two clear moraine sets. Data from La Mare Glacier indicate the first advance occurred prior to 12.3±0.7 ka (before 10.0±0.7 ka at Careser Glacier). Both glaciers then re-advanced before 11.2±0.8 ka as dated at La Mare Glacier. This phase can be interpreted as the Egesen stadial glaciers' expression of the end of the YD. Morphometric parameters of the reconstructed phases allowed the estimation of areal and volumetric variations of the studied glaciers as well as equilibrium line altitude ( ELA). Δ ELA with respect to the Little Ice Age ( LIA) maximum position are −225 m for La Mare Glacier and −180 m for the Careser Glacier. Although the behaviour of the two glaciers showed coherence during the Egesen stadial and the LIA, they have behaved individually since then. La Mare has lost 60% of its area, while Careser has lost 85% since the latest Pleistocene. We attribute this to the greater proportion of ice at high elevation of the La Mare Glacier, underlining the importance of bed hypsometry in glacier response. [ABSTRACT FROM AUTHOR]

Field observations, old terrestrial photographs and maps, aerial orthophotos and detailed geomorphological mapping were used for compiling and validating a 119-year cumulative record of terminus changes for La Mare Glacier, Eastern Italian Alps. Late Holocene glacier maxima preceding direct observations were reconstructed by applying age dating techniques (radiocarbon and lichenometry) to glacial deposits in the proglacial area of the glacier. Results show that the glacier reached its maximal position around 1600 ad, followed by smaller advances in the eighteenth century, while in the nineteenth century it did not reach or overrun these positions. A similar behaviour for neighbouring glaciers was reported by previous works, documenting absolute Late Holocene maxima in the seventeenth or eighteenth centuries. By contrast, multi-century reconstructions available for the north-western Alps show that in the nineteenth century, glaciers were at their maximum or very close to previous maxima achieved in the first half of the seventeenth century. Climatic causes for these discrepancies have been examined, analyzing multi-proxy climatic reconstructions starting in 1500 ad, but also morphodynamic processes linked to the bedrock characteristics of La Mare Glacier could have played a role in modulating its response to climatic changes. [ABSTRACT FROM AUTHOR]

• In the study area glaciers have lost 50% of their total surface since LIA. • Slope processes favour alpine plant colonization across the treeline ecotone. • Microrefugia offer climatic shelter reducing the extinction risk for alpine species. • Alpine plants could be less prone to decline than predicted by ecological models. The temperature rise at the global level and glacier shrinkage are deemed to induce new dynamics between biotic and abiotic factors, especially in mountain regions. In this work, we aimed to assess: (a) the area made available after glacier retreat since the Little Ice Age (LIA) for the colonization of alpine plants; (b) the ability of 14 alpine and nival species, typically growing on peaks and in deglaciated areas, to migrate and survive at lower elevations in microrefugia across the treeline ecotone. In the Adamello-Presanella Massif (Rhaetian Alps), we collected presence data on 14 alpine species within 3 × 3 or 5 × 5 m plots according to slope landforms and deposits. The analysis of the elevation range of the investigated species across the treeline was performed using Sentinel-2 satellite images to derive the actual position of the upper and lower treeline. The differences in the species elevation ranges across slope landforms, in relation to the treeline elevation and aspect, were detected with linear mixed models. Results showed that glaciers contracted sharply by more than 50% between the LIA and 2006, making large deglaciated areas available (more than 57 km2). All the studied species were found at low altitudes across the treeline ecotone, from about 500 to 1200 m below their typical habitat. Six species (Cardamine resedifolia , Cerastium uniflorum , Leucanthemopsis alpina , Luzula alpinopilosa , Oxyria digyna , Saxifraga oppositifolia) significantly exceeded the upper treeline in correspondence of alpine composite channels (p < 0.001 for all species). One species (Adenostyles leucophylla) exceeded the upper treeline in correspondence of composite slope deposits (p < 0.05). Two species (Ranunculus glacialis and S. oppositifolia) reached the lower treeline in composite channels and slope deposits (p = 0.800, and p = 0.519, respectively). The retreat of the alpine glaciers, coupled with the intensification of paraglacial processes, may favor new habitat opportunities at high elevation and microrefugia at low altitudes for nival and alpine species. The widespread presence of microrefugia for alpine plants downslope during warm periods suggests a low incidence of biodiversity loss in the alpine regions due to climate change. [ABSTRACT FROM AUTHOR]