Knowledge of the glacial chronologies for the Last Glacial Maximum (LGM) helps in understanding the interactions between climate, topography and glacier development. In this sense, the investigation of the Lake Orta moraine amphitheatre (Alpine foreland, northern Italy) allowed spatial and temporal reconstruction of the Orta Glacier. The end‐moraine system was investigated by means of geomorphological field surveys, analysis of 13 rock samples for cosmogenic 10Be and 36Cl concentrations, and remote sensing analysis. The dating results indicate that the age of the outer moraine belt is concordant with the LGM culmination at 26.5–23 ka, as found in other amphitheatres in the Alps. This new age estimate of the outermost moraines shows that the maximum extent of the Orta Glacier during the LGM was significantly bigger than recently suggested. A younger stabilization phase of the glacier front at about 19 ka indicates that the onset of the withdrawal of glaciers from the lower Alpine valleys started later. Provenance analysis of the boulders shows that the greatest contribution of ice to the Orta Glacier came from the Anzasca Valley rather than the major Ossola Valley. This reflects the closeness (about 45 km) to the foreland of the high‐elevated accumulation area of the Monte Rosa massif (4634 m a.s.l.), whose eastern glacier seems to have reached the lower valley faster than the trunk Toce Glacier. This fact underlines the key role played by high‐elevation accumulation areas that are located close to the foreland in controlling the path and geometry of major glaciers in the Alps.

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). ΔELA 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. Quantitative satellite observations provide a comprehensive assessment of ice sheet mass loss over the last four decades, but limited insights into long-term drivers of ice sheet change. Geological records can extend the observational record and aid our understanding of ice sheet–climate interactions. Here we present the first millennial-scale reconstruction of David Glacier, the largest East Antarctic outlet glacier in Victoria Land. We use surface exposure dating of glacial erratics deposited on nunataks to reconstruct changes in ice surface elevation through time. We then use numerical modelling experiments to determine the drivers of glacial thinning. Thinning profiles derived from 45 10Be and 3He surface exposure ages show that David Glacier experienced rapid thinning up to 2 m/yr during the mid-Holocene (~ 6,500 years ago). Thinning stabilised at 6 kyr, suggesting initial formation of the Drygalski Ice Tongue at this time. Our work, along with terrestrial cosmogenic nuclide records from adjacent glaciers, shows simultaneous glacier thinning in this sector of the Transantarctic Mountains occurred ~ 3 kyr after the retreat of marine-based grounded ice in the western Ross Embayment. The timing and rapidity of the reconstructed thinning at David Glacier is similar to reconstructions in the Amundsen and Weddell embayments. In order to identify the potential causes of these rapid changes along the David Glacier, we use a glacier flow line model designed for calving glaciers and compare modelled results against our geological data. We show that glacier thinning and marine-based grounding line retreat is initiated by interactions between enhanced sub-ice shelf melting and reduced lateral buttressing, leading to Marine Ice Sheet Instability. Such rapid glacier thinning events are not captured in continental or sector-scale numerical modelling reconstructions for this period. Together, our chronology and modelling suggest a ~ 2,000-year period of dynamic thinning in the recent geological past.

Abstract. Quantitative satellite observations only provide an assessment of ice sheet mass loss over the last four decades. To assess long-term drivers of ice sheet change, geological records are needed. Here we present the first millennial-scale reconstruction of David Glacier, the largest East Antarctic outlet glacier in Victoria Land. To reconstruct changes in ice thickness, we use surface exposure ages of glacial erratics deposited on nunataks adjacent to fast-flowing sections of David Glacier. We then use numerical modelling experiments to determine the drivers of glacial thinning. Thinning profiles derived from 45 10Be and 3He surface exposure ages show David Glacier experienced rapid thinning of up to 2 m/yr during the mid-Holocene (∼ 6.5 ka). Thinning slowed at 6 ka, suggesting the initial formation of the Drygalski Ice Tongue at this time. Our work, along with ice thinning records from adjacent glaciers, shows simultaneous glacier thinning in this sector of the Transantarctic Mountains occurred 4–7 kyr after the peak period of ice thinning indicated in a suite of published ice sheet models. The timing and rapidity of the reconstructed thinning at David Glacier is similar to reconstructions in the Amundsen and Weddell embayments. To identify the drivers of glacier thinning along the David Glacier, we use a glacier flowline model designed for calving glaciers and compare modelled results against our geological data. We show that glacier thinning and marine-based grounding-line retreat are controlled by either enhanced sub-ice-shelf melting, reduced lateral buttressing or a combination of the two, leading to marine ice sheet instability. Such rapid glacier thinning events during the mid-Holocene are not fully captured in continental- or catchment-scale numerical modelling reconstructions. Together, our chronology and modelling identify and constrain the drivers of a ∼ 2000-year period of dynamic glacier thinning in the recent geological past.

In this paper, we supply a geological map of the area between 76°-76°30 ′ S and 159°-163°E, that was the only missing portion to complete an entire coverage of Victoria Land, filling the gap between the GIGAMAP program (to the north) and the maps by the New Zealand Antarctic program (to the south). The mapped area encompasses an early Paleozoic basement, and a flat-lying cover of sedimentary and igneous rocks, Permo-Triassic to Jurassic in age. The basement consists of large bodies of the Granite Harbour Igneous Complex, a granitic complex linked to the Ross Orogeny. After the early Paleozoic Ross Orogeny, the area was uplifted and eroded, and the sandstones of the Beacon Supergroup were deposited on the resulting erosion surface. The Beacon Supergroup sandstones were in turn covered and in most cases incorporated into the volcanic and sub-volcanic rocks of the Jurassic Ferrar Group.