Search

In the piedmont of uplifting mountains, alluvial fan rivers undergo significant aggradation-degradation processes, which are usually attributed to climate change. An ongoing debate is whether this process requests the participation of glaciation. To address this debate, we need the knowledge of the quantitative relationship between the ratio of water to sediment flux (q w / q s) with the aggradation/degradation process. This study examined the aggradation and degradation processes in three alluvial rivers at the piedmont of the Qilian Shan (Shan referes to Mountain) and simulated the river processes by a one-dimensional numerical model based on the transport-limited principle. Along the studied piedmont rivers, field measurements show a magnitude of 120–200 m degradation and aggradation in the Late Pleistocene. Through simulation analysis, we explored how factors like the ratio of water to sediment flux (q w / q s), channel width, and sediment grain size influence river processes and longitudinal profiles, and found distinct morphologies in different processes, where aggradation is characterized by concave-up profiles, while degradation is characterized by convex-down profiles. Additionally, the water flux is inversely proportional to the time required for the river to reach a new equilibrium profile. The simulated degradation amplitude aligns closely with the measured data in the Qilian Shan, indicating that precipitation during the Last Glacial Maximum in the region amounted to approximately ∼32% of the Holocene precipitation. This supports the notion that changes in water flux or precipitation alone can induce significant piedmont deepening without the necessity of glaciation. • Built a model to quantify the link between water-sediment fluxes and river processes. • Simulated Qilian Shan piedmont river incision: ∼32% LGM precipitation vs. Holocene. • Precipitation alone can create deep canyons without requiring glaciation. [ABSTRACT FROM AUTHOR]

Little information is available about the origin of loess on the Iranian Loess Plateau and along the northern foothills of the Alborz mountain range. Our well-dated multiproxy record from the Chenarli loess-paleosol sequence (LPS) fills this gap and provides a valuable paleoclimate record. Eight loess units are identified , covering the late penultimate glacial period (Marine Isotope Stage (MIS) 6: 135.6 ± 9.5 ka) until the Early Holocene (9.8 ± 0.7 ka). Geochemical results propose a constant local primary loess source with a longer transport distance only for MIS 5b and MIS 5d loess. However, low Si/Ti but high Zr/Ti ratios and increased sand contents of MIS 6 loess are implying stronger winds and derivation of this loess from a different source containing coarser particles. We interpret our data in a regional context and compare periods of loess deposition and pedogenesis in northern Iran with other loess records from Southern Eurasia. This indicates that late Pleistocene pedogenesis recorded at Chenarli agrees with periods of paleosol formation at LPS from northern Iran and Southern Eurasia. A ∼9-m thick loess deposition between ∼62 and 16 ka in unit 2 at Chenarli is consistent with other loess records indicating significant loess accumulation during MIS 3 with a peak during the Last Glacial Maximum in Southern Eurasia. One of the paleosols at Chenarli correlates with the late MIS 4 interstadial, which is well-recorded in southern Eurasian loess deposits. The geochemistry of loess and paleosols at Chenarli provides new information about the origin of loess in north and northeastern Iran where the sources of eolian deposition are still not well understood. • Eight loess units are identified spanning the past 135 ka, separated with paleosols. • Geochemical results indicate a constant local primary loess source for all loess units in the section. • Results indicate a longer transport distance from sources for MIS 5b and MIS 5d loess. • Particle size and geochemical data suggest that nearby sources with local sand contributions for MIS 6 loess. [ABSTRACT FROM AUTHOR]

Previous paleo-glacial studies on Kerguelen showed a singular pattern of Holocene glacier evolution on this archipelago in comparison with other southern mid-latitude glacier records. In this study, we aim to test this singularity on a longer timescale, based on 26 new in situ -produced 36Cl ages from pre-Holocene glacio-geomorphic features. Samples from moraine boulders and glacially polished bedrock were extracted at six different sites, located near the Port-aux-Français scientific station (PAF site), on Longue Island, Australia Island, on the Port-Jeanne d'Arc Peninsula (PJDA site), on the Gallieni Peninsula at Baie Larose (BLR site) and the McMurdo Island. The moraine ages indicate that glacier culminations occurred during Marine Isotopic Stage 3 (MIS 3) at 42.2 ± 4.9 ka on the PAF site, and during the global Last Glacial Maximum (gLGM) at 21.5 ± 3.2 ka on the PJDA site and at 21.4 ± 3.7 ka and 19.4 ± 2.6 on Baie Larose site. This is the first time that Late Pleistocene glacier culminations are evidenced on Kerguelen by direct moraine dating, thus allowing comparison with other moraine records from the southern mid-latitudes. While it remains speculative whether or not the MIS 3 glacial maximum at ⁓42.2 ka is in phase with other glaciers at this latitude (due to high age uncertainties), the gLGM glacial maximum is synchronous with that in other southern mid-latitude regions. 36Cl CRE ages of glacially polished bedrock surfaces sampled in different locations of the archipelago vary from ⁓39 ka to ⁓19 ka. We interpret these results as reflecting periods of deglaciation that occurred in between the two glacier culminations and right after the gLGM on Kerguelen. These ages also suggest that some places of the archipelago were free of ice at least since ⁓ 39 ka. The presence of a MIS 3 moraine at PAF site that has not been obliterated by a gLGM advance suggests that the ⁓ 42.2 ka glacier extent was at least as large as gLGM glacial maxima on the archipelago. The glacier culmination during MIS 3 being larger than that during the gLGM on the Kerguelen Archipelago matches observations in other southern mid-latitude regions. Late Pleistocene glacier culminations on Kerguelen may have been in phase with cold temperatures recorded in SST records, which suggest a cooling around Kerguelen. However, climate drivers responsible for the larger MIS 3 glacier culmination on Kerguelen still remain unclear even if we hypothesize that changes in precipitation may have superimposed on temperature changes. • We investigate glacier evolution on the Kerguelen Archipelago for the past 45 ka. • Glacier chronologies are based on 26 new 36Cl ages from moraines and bedrocks. • Preserved moraines attest to glacier culminations at ∼42 ka and during the LGM. • Evidence of larger MIS 3 than gLGM glacier culmination. • This pattern matches records from other southern mid-latitude regions. [ABSTRACT FROM AUTHOR]

The southern limit of the Patagonian Ice Sheet at glacial maxima is poorly constrained due to a paucity of field data. This particularly applies to southern outlet glaciers of the Cordillera Darwin whose full extents have been debated by glacial geologists since 1899 CE, introducing uncertainty into estimates of total ice volume. Here we report on the stratigraphy of exposed stratigraphic sections on the west coast of Isla Hermite which include glacial diamict with discontinuous boulder pavement, overlain by successions of peats and sandy silt. The location of these sections, orientation of clasts within the glacial diamict, and geomorphology of the adjacent marine trough, suggest that an ice stream extended south from an ice centre at Cordillera Darwin across an extended Magellan outwash plain, through Paso Mantellero, to Islas Hermite and Cabo de Hornos (Cape Horn). This was similar in extent to the Canal Beagle and Lago Fagnano Ice Lobes which extended to the east. Retreat occurred sometime before 12,880 cal yr BP based on radiocarbon dated peat macrofossils immediately overlying the glacial diamict. We discuss whether this is a close minimum age, or a product of delayed onset of peat accumulation at the sampling site. • Glacial tills described on the west coast of Isla Hermite. • Confirm Paso Mantellero ice lobe extended from Cordillera Darwin to Cape Horn. • This marks the southern limit of the Patagonian Ice Sheet during the last glacial. • Maximum ice extent occurred sometime before 12,880 cal Yr BP. • Peat accumulated on Isla Hermite from 15,400 cal Yr BP. [ABSTRACT FROM AUTHOR]

The continuous record offered by deep-sea sediments has been extensively used to constrain shifting continental and oceanographic conditions. Yet, past fluctuations in deep-sea benthic conditions and bottom-currents are in numerous parts of the globe scarcely documented, one such example being the South Australian margin. Indeed, though variations in surface water masses and continental aeolian dust and river outflow are well documented in the area, little is known about benthic environments and their dynamics during the last interglacial-glacial cycle. We focus here on benthic foraminiferal assemblages sampled from a sediment core recovered at 2420 m depth from a small plateau south of Kangaroo Island within the underwater Murray Canyons Group (South Australian margin). Benthic foraminiferal assemblages show a distinct separation between interglacial and glacial periods over the last 94 ka, and indicate that the benthic environment was well-ventilated and oligotrophic during glacial periods, whilst being rather marked by reduced oxygenation associated to higher food input during the Holocene and Marine Isotope Stage 5a-c. We demonstrate that autochtonous deep-sea benthic foraminiferal communities neither respond to changes in the Murray River's discharges, nor do they follow variations in aeolian dust input from South Australia. Instead, the deep-sea and the terrestrial realm appear decoupled. Moreover, our observations suggest that bottom-water slope currents were stronger during the Holocene and Marine Isotope Stage 5a-c. We propose that this strengthening was triggered by an intensification of the poleward-circulating deep eastern boundary current transporting carbon-rich Indian Deep Water. In contrast, glacial seafloor conditions, especially during the Last Glacial Maximum, may reflect a greater influence and a shoaling of oxygen-rich Antarctic Bottom Water of South Australia. This bottom-water shift would follow the northward displacement of the Subtropical and Subantarctic Fronts and coincide with a withering influence of the Leeuwin Current within surface waters. • The benthic environment was well-ventilated and oligotrophic during glacials • Reduced-oxygenation and higher nutrient input characterize warm periods • The deep-sea and the terrestrial realm appear decoupled during the last 94 ky • Interglacial foraminifera evidence a strengthening of bottom-water slope currents • Shoaling of oxygen-rich Antarctic Bottom Water may explain the glacial microfauna [ABSTRACT FROM AUTHOR]

We test the hypothesis that glacier systems, located in continental regions proximal to the Laurentide Ice Sheet (LIS), had local ice maxima considerably earlier than the LIS maximum and thus before the insolation minima at ∼21 ka. Ranges located in the northwest US exhibit earlier deglaciation timing between ∼23 and 22 ka, except for the Yellowstone region where younger time-transgressive ages complicate regional interpretations and the northern Montana ice cap where late glacial ages have recently been produced. Constraining the glacial history of more ice sheet-proximal alpine glaciers provides insight into whether the contrasting maximum-ice times in the northern Rocky Mountains were caused by regional climatic differences, such as anticyclonic wind patterns driven by the presence of the LIS. In the Pioneer Mountains of Montana, we measured in situ cosmogenic 10Be in 35 boulders on moraines marking the maximum Late Pleistocene positions of alpine glaciers from three valleys. The 10Be samples produced a range of ages, spanning pre Bull Lake to the last glaciation (i.e., Pinedale/Marine Isotope Stage (MIS) 2). We find an average exposure age for initial deglaciation of 18.2 ± 0.9 during the local Last Glacial Maximum, indicative of synchronous retreat in the Pioneer Mountains. The similarity of initial deglaciation timing of the Pioneer Mountain glaciers with the northwestern Yellowstone glacial system and northern MT ice cap suggests that topography more proximal to the LIS margin maintained full ice extent longer. Our findings, in context of previous work, suggest that in the case of the Pioneer Mountains their more proximal location to the ice margin may have delayed onset of deglaciation by greater exposure to local cooling from katabatic winds and/or additional moisture sourced from large ice-marginal glacial lakes, hence the lack of earlier deglacial ages like those found further to the west and east of the northern Rocky Mountain cordillera. [ABSTRACT FROM AUTHOR]

We present a 3D reconstruction of ice thickness distribution across the New Zealand Southern Alps at the Last Glacial Maximum (LGM, c. 30–18 ka). To achieve this, we used a perfect plasticity model which could easily be applied to other regions, hereafter termed REVOLTA (Reconstruction of Volume and Topography Automation). REVOLTA is driven by a Digital Elevation Model (DEM), which was modified to best represent LGM bed topography. Specifically, we removed contemporary ice, integrated offshore bathymetry and removed contemporary lakes. A review of valley in-fill sediments, uplift and denudation was also undertaken. Down-valley ice extents were constrained to an updated geo-database of LGM ice limits, whilst the model was tuned to best-fit known vertical limits from geomorphological and geochronological dating studies. We estimate a total LGM ice volume of 6,800 km3, characterised predominantly by valley style glaciation but with an ice cap across Fiordland. With a contemporary ice volume of approximately 50 km3, this represents a loss of 99.25% since the LGM. Using the newly created ice surface, equilibrium line altitudes (ELAs) for each glacier were reconstructed, revealing an average ELA depression of approximately 950 m from present. Analysis of the spatial variation of glacier-specific ELAs and their depression relative to today shows that whilst an east-west ELA gradient existed during the LGM it was less pronounced than at present. The reduced ELA gradient is attributed to an overall weakening of westerlies, a conclusion consistent with those derived from the latest independent climate models. • LGM ice thickness reconstructed on a glacier-by-glacier basis, driven by geomorphological evidence. • During the LGM the Southern Alps contained approximately 6,800 km3 ice, of which 99.25% has subsequently been lost. • Predominant valley style of glaciation across Southern Alps but ice cap across Fiordland. • The spatial patterns of precipitation and temperature were markedly different at the LGM compared to present. • Westerly circulation was apparently reduced during the LGM when compared to present. [ABSTRACT FROM AUTHOR]

Ravine slopes at the recently discovered Nesseltalgraben site in southeastern Germany provide a unique last glacial sediment record for the Northern Calcareous Alps. The 21 m-long profile is dominated by fine-grained lacustrine-palustrine sediments overlain by several metres of glacifluvial gravels and lodgement tills of the Last Glacial Maximum and underlain by a diamicton. The age model includes 29 radiocarbon analyses and one paleomagnetic anomaly (Laschamp event) together providing a modelled age range from c. 59 to 29.6 ka cal BP, i.e. Marine Isotope Stage (MIS) 3. Apart from a description of the lithofacies, X-ray-fluorescence (XRF) scanning and elemental analyses provide high-resolution records of the geochemical composition. Multivariate analyses of XRF data separate Ca from other major elements. Carbonate contents, represented by Ca and total inorganic carbon, reach maxima in repeatedly occurring calcareous silty to sandy layers and are related to glacigenic origin. These indicate repeated inner-alpine local glaciations during stadials of MIS 3. Scanning electron microscopy and XRF data confirm the detrital origin of these layers. In contrast, organic matter and elements more resistant to chemical weathering (Si, Ti, Zr) accumulated during interstadials and concurrently elevated Rb/Sr ratios indicate intensified weathering. The high-frequency proxy variations determined for Nesseltalgraben reflect interstadial-stadial climate variability comparable with oxygen-isotope records from Greenland ice cores and Alpine speleothems. Thus, Nesseltalgraben is among the very few independently dated sediment records from continental Europe covering the entire MIS 3 and reflecting the full Dansgaard-Oeschger climate variability. • A 21 m sediment profile from the northern Alps provides a complete MIS 3 record. • Repeated inner Alpine glaciations are indicated by calcareous silt layers. • Geochemical variations reflect interstadials and stadials. • The Nesseltalgraben record resembles Dansgaard-Oeschger climate variability. [ABSTRACT FROM AUTHOR]

We present a new speleothem trace element and stable isotope record, which extends previous paleoclimate evidence from Cuban speleothems to the last 96 ka. Multiple proxies were used to reconstruct Caribbean hydroclimate and vegetation variability on orbital to millennial timescales. In particular, our proxies indicate a shift to more abundant C4 (compared to C3) vegetation and/or reduced soil activity during the Last Glacial Maximum. Our results confirm the close link of Caribbean precipitation to North Atlantic climate variability, insolation and the strength of the AMOC. The associated variations in Caribbean SSTs and the shift of the ITCZ led to substantial changes of the hydrological cycle. During Heinrich stadials and the Younger Dryas, climatic conditions in Cuba were comparably cool and/or dry. In contrast, warm Dansgaard/Oeschger cycles were accompanied by wetter conditions. This is in agreement with previous evidence for the Holocene, when North Atlantic cold (warm) events coincided with drier (wetter) conditions in Cuba. However, our record suggests that this connection was less dominant during MIS 4 to 2, displayed by a weaker response of Cuban precipitation proxies to North Atlantic climatic shifts than during MIS 5 in particular. We hypothesize that this weaker connection was mediated by the southerly shifted ITCZ inducing a weakening of the northern branch of the Caribbean Low Level Jet which usually transports moisture into the northern Caribbean. This is strikingly evident during the deglacial, when driest and/or coolest conditions prevailed in western Cuba from HS 1 into the Younger Dryas, including the Bølling/Allerød interstadial. • We present a speleothem stable isotope and trace element record from Cuba covering the last 96 ka. • Our results confirm the link of Caribbean precipitation to NA climate, insolation and the AMOC. • Last glacial NA cold (warm) (inter)-stadials coincided with drier (wetter) conditions in Cuba. • During the LGM, our data suggest a shift to more abundant C4 vegetation and/or reduced soil activity. • We observe a weaker sensitivity to NA climate during MIS 4 to 2 compared to MIS5 and the Holocene. [ABSTRACT FROM AUTHOR]

The study reports new progress in the glacial chronology from new sites of the Chandrabhaga basin (CBB), in the transition between the monsoon-dominated Pir-Panjal and westerly-dominated Trans-Himalaya, in Lahaul Himalaya, northern India. In Lahaul, asynchronous timing and extent of late Quaternary glaciation have been reported (Owen et al., 1996, 1997, 2001; Eugster et al., 2016). The established oldest and most extensive Chandra glacial stage remains undated and speculative. We reconstrain the late Quaternary glacial history of the CBB using geomorphological mapping, Infrared Stimulated Luminescence (IRSL), and 10Be Terrestrial Cosmogenic Nuclide (TCN) surface exposure dating. Four local glacial stages, the Chandra, Batal, Dali, and Mayar, are dated to 152 ± 37 ka, 43 ± 3 ka, 21 ± 2 ka, and Little Ice Age (LIA), respectively. The Chandra glacial stage occurred during the late Marine Isotope Stage 6 (MIS 6; 186 ± 30 – 113 ± 10 ka), characterized by thick lacustrine deposits, rock benches, and ice-polished bedrock along the trunk valleys. We provide the first account of the numerical dating for the much-awaited timing of the oldest Chandra glacial stage (Local Last Glacial Maxima; LLGM) in the region (Owen et al., 1996, 1997, 2001). The LLGM in the CBB is much older than previously thought, consistent with some north-western Himalayan glacial records (Owen et al., 2006; Dortch et al., 2010; Hedrick et al., 2011; Orr et al., 2017, 2018). The Batal glacial stage occurred during the early MIS 3 and is dated from 47 ± 2 to 41 ± 2 ka, represented by the thick lacustrine deposits and impressive terraces. The Dali glacial stage occurred during the Global Last Glacial Maxima (GLGM), characterized by a series of latero-frontal recession moraines, and is dated from 33 ± 3 to 13 ± 1 ka. The Mayar advance is characterized by confined tributary valley glaciers, possibly linked to the LIA advance reported in the Kulti valley (Saha et al., 2019). The equilibrium line altitude (ELA) rose by ∼486 m from the Chandra stage to the present day. Reconstructed ELA altitudes and glacial landforms demonstrate that the glaciations have become progressively less extensive through time for this part of the western Himalayas. The change of glaciation pattern during the later part of the Quaternary is like other regions of the orogen, such pattern of glaciation reflects regional climatic forcing. • We present novel 31 k-feldspar IRSL and 12 cosmogenic 10Be ages for Chandrabhaga basin, Lahaul Himalaya, northern India. • We reconstrain the chronology for previously reported glacial stages of Owen et al. (1996, 1997, 2001). • We assign previously reported but undated oldest Chandra glacial stage with absolute dates. • Findings suggest that the Local Last Glacial Maxima in this region is much older than previously thought. • Our findings strongly question the previously reported extensions and rate of deglaciation during Global Last Glacial Maxima by Eugster et al. (2016). • Each glaciation becomes progressively less extensive in the Chandrabhaga basin over time. [ABSTRACT FROM AUTHOR]

Substantial stratigraphic evidence from the Late Quaternary at orbital- and millennial‒scales indicates that the formation and evolution of aeolian‒sand landscapes results from the interaction between regional aeolian and fluvial‒lacustrine activity. In many deserts (sandy lands) across the planet, fluvial‒aeolian interplay at the glacial‒interglacial scale since the Late Quaternary has been responsive to monsoonal precipitation, and linked to atmospheric CO 2 and periodic variations in insolation. However, the patterns of fluvial‒aeolian interplay and their relationship with climate change are not always consistent over a given timescale during the Late Pleistocene. The paucity of studies on fluvial‒aeolian interplay in the Mu Us Desert (MUD) during the Last Glacial Period (LGP) hinders our understanding of the relationships between the dynamics of aeolian and fluvial‒lacustrine landscapes and their drivers. Here, based on a comprehensive field survey and stratigraphic dating of a typical fluvial‒aeolian sequence in the MUD, we synthesized the chronology of fluvial‒lacustrine and aeolian strata during the LGP. Our results show that extensive development of a fluvial‒lacustrine environment in the MUD during the LG mainly occurred during the late Last Glacial Maximum (LGMa, 20.1–18.4 ka BP) and Bølling/Allerød interstadial (14.8–12.6 ka BP), while thicker aeolian sands extensively accumulated during the Heinrich Stadial 2, Heinrich Stadial 1, and Younger Dryas periods. However, the development of fluvial‒lacustrine environments showed considerable spatial heterogeneity, mainly occurring on the southern and eastern margins of the desert, while they were extremely rare in the central and western parts of the desert owing to strong wind erosion. Comparisons with other high-resolution geological records from the Asian monsoon region reveal that the fluvial‒aeolian interplay in the MUD during the LGP was highly consistent with the evolution pattern of the East Asian summer monsoon (EASM) on the millennial‒centennial scale, and indicate that the development of fluvial‒lacustrine environments was mainly controlled by an increase in monsoonal precipitation during strengthening of the EASM. Consistency with other broad changes at high latitudes in the Northern Hemisphere suggests that fluvial‒aeolian interplay during the LGP in northern Chinese deserts, as represented by the MUD, was mainly controlled by changes in high-northern-latitude ice volume and the Atlantic Meridional Overturning Circulation. • Fluvial‒aeolian interplay during the Last Glacial Period in the Mu Us Desert is studied. • Regional fluvial‒aeolian interplay during the LGP is correlated with millennial-scale global climatic events. • Regional fluvial‒lacustrine environments mainly developed during the LGMa and B/A. • Fluvial‒lacustrine and aeolian processes during the LGP were mutually reinforcing and inhibiting. • High-northern-latitude forcing modulated millennial-scale fluvial‒aeolian interplay in the MUD during the LGP. [ABSTRACT FROM AUTHOR]

The area of Prados del Cervunal (PC) is an intra-morainic topographic depression located at 1800 m asl in the divide or interfluve between Garganta de Gredos and Garganta del Pinar valleys (Central Gredos; Iberian Central System, ICS). Both valleys, along with the adjacent Hoya Nevada, were occupied by glaciers during the Upper Pleistocene, leading to the development of the Prados del Cervunal moraine complexes studied in this work. Using cartographic methods and morphostratigraphic analysis, the three main glacial formations established in the Regional Chrono-Evolutionary Pattern for the ICS, Peripheral Deposits (PD), Principal Moraine (PM) and Internal Deposits (ID), have been identified and mapped in this area. The chronology of these formations has been implemented by Cosmic Ray Exposure (CRE) techniques using 10Be (new data) and 26Cl (previous data, recalculated in this work) in samples from morainic boulders. With these data, the following chrono-evolutionary sequence has been established: (stage 1) local-Maximum Ice Extent (MIE), dated in 25.0 ± 1.4 ka and corresponding to the maximum age obtained in these paleoglaciers; (stage 2) period of oscillations around the MIE, corresponding to the development of the PD Formation between ∼25 ka and ∼21 ka; (stage 3) period of readvance and stabilisation, dated after ∼21 ka (average age obtained for the PD moraines attached to PM moraines) and previous to ∼18 (minimum age obtained for a main crest of the PM formation); and (stage 4) onset of deglaciation dated around to ∼18 ka (average of ages obtained for the first main crest of the ID formation). During the stages of maximum ice expansion, these three glaciers formed an Ice field whose tongues were interconnected on the PC flat by an ice transfluence system (stages 1 and 2, Plateau Glacier Period). In later stages, the ice masses were partitioned, giving rise to valley glaciers and large moraines forming morainic complexes like those of PC (stages 2, 3 and 4, Valley Glaciers Period). The local MIE and onset of deglaciation stages in this area show a good fit with the ages stablished to global level for the global Last Glacial Maximum (LGM) and the onset of the Last Glacial Termination (Termination I). They also show good correlation at local (with other areas of the ICS), peninsular (with other Iberian mountains) and continental (some areas of the Alps and mountains of Central Europe) level. Finally, this evolutionary sequence and its correlations allowed us to adjust and validate some units of the Regional Chrono-Evolutionary Pattern model and propose the Gredos-Pinar-Cabeza Nevada glacial system as benchmark for the glaciation of Marine Isotope Stage (MIS) 2 in the Iberian Peninsula. • Glacial Geomorphology in Gredos-Pinar-Hoya Nevada paleoglaciers (Sierra de Gredos) was established. • New chronological data using 10Be-CRE and previous data using 36Cl-CRE allowed precise dating of the morainic sequence. • Previous morphology, aspect and debris supply as control factors of the layout and the dynamic of ice masses. • The local-MIE and the subsequent major readvance stage occurred within the LGM period. • Model from MIS 2 glaciation in the area: MIE and readvance post-MIE intra-LGM immediately followed by Termination-I. [ABSTRACT FROM AUTHOR]

The Southern Hemisphere Westerlies (SHW) and their linkages with key ocean and atmospheric processes have the potential to drive abrupt climate change. The westerlies migrate seasonally and are thought to have shifted during past climate events, such as the last glacial termination. However, the timing, magnitude, direction, and mechanisms behind such shifts remain a topic of ongoing study. Here, we contribute to the understanding of past temporal and spatial changes in the SHW by mapping their fluctuations in the South Atlantic region from the last glacial maximum (LGM) to present. We use lake sediment proxies, including plant wax isotopes extracted from two tarns on Mt. Usborne, East Falkland (51.7 °S) to infer changes in paleoclimate and in the mean annual position of the SHW over the last ∼23,000 years. Together, the proxies indicate that the position of the SHW during the LGM lay north of the Falkland Islands. We interpret our plant wax isotopic record as showing a southward migration of the mean annual position of the wind belt beginning just before ∼21 ka, accompanied by warming at Mt. Usborne at ∼16.5 ka. The late-glacial climate was variable at the field site, and the mean annual position of the SHW may have fluctuated around the latitude of the Falkland Islands. The early Holocene was characterized by relatively warm, dry conditions with high evaporation rates, and the SHW may have lain south of the islands. A brief southern excursion at 7–6 ka was followed by gradual northward migration of the SHW for the remainder of the Holocene to the pre-industrial position. This northward migration was paired with increasingly wet, cool conditions in the Falkland Islands, and the islands appear to be experiencing some of the wettest conditions of the last 23,000 years during the late Holocene. • Lake sediment proxies from East Falkland track the SHW over the last 23,000 years. • SHW moved south at ∼21 ka before reversing the trend at the start of the Holocene. • The SHW fluctuated near the Falkland Islands during the late glacial period. • The early Holocene was warm with high evaporation, and a southern SHW position. • The SHW migrated north in the second half of the Holocene. [ABSTRACT FROM AUTHOR]

Proglacial lakes can affect the stability of mountain glaciers and can partly disengage glacier behaviour from climatic perturbations. However, their role in controlling the onset and progression of deglaciation from the Last Glacial Maximum (LGM) remains poorly understood. This lack of understanding is partly because the evidence required to consistently and robustly identify the location and evolution of ice-contact lakes is not standardised. In this paper we therefore firstly present a new set of criteria for identifying the landform and sedimentary evidence that defines and characterises ice-marginal lakes. Secondly, we then apply these key criteria with the aid of high-resolution topographic mapping to produce the first holistic definition and assessment of major proglacial lake landforms and sediments pertaining to the end of the LGM across South Island, New Zealand. The major findings of this assessment can be grouped to include that: (i) The localised constraints to proglacial lake extent were topography, glacier size and meltwater/sediment fluxes, (ii) Lake damming was initiated by outwash fan-heads that interrupted water and sediment flows down-valley, and (iii) New Zealand LGM lakes were unequivocally in contact with a calving ice margin. These findings will be useful for reconstructing ice dynamics and landscape evolution in this region. • Key criteria to identify, characterise and interpret landforms and sediments associated with ice-contact proglacial lakes. • Exploitation of high-resolution LiDAR topographic data for proglacial lakes across South Island, New Zealand. • Synthesis analysis of the 3D geometry, landforms and sediments, and interpretation of the evolution of New Zealand LGM lakes. [ABSTRACT FROM AUTHOR]

Here we summarize the motivation and issues surrounding the responses of ice sheets and sea level to past climate warming as part of the PALeo constraints on SEA level rise (PALSEA) working group. Papers in this special issue of Quaternary Science Reviews focus on the timescale of glaciations during the late Pliocene, the magnitude of ice-sheet fluctuations and volume leading up to and during the last glacial maximum, the timing and persistence of ice-sheet impacts on deglacial and future relative sea-level change, and relative sea-level change during peak interglacial climate. A more dynamic cryosphere is noted under both late Pliocene and last glacial cycle climate conditions, while relative sea-level changes during the last deglaciation appear to correspond closely with individual ice-sheet deglaciation. Lastly, relative sea-level change during peak interglacial conditions may have fluctuated by as much as a meter, although the sources of such variability (Greenland, Antarctica or elsewhere) remain elusive. [ABSTRACT FROM AUTHOR]

Calculating cosmogenic-nuclide surface-exposure ages is critically dependent on a knowledge of the altitude of the sample site. Changes in altitude have occurred through time as a result of glacial isostatic adjustment (GIA), potentially altering local nuclide production rates and, therefore, surface-exposure ages. Here we assess the impact of GIA on surface-exposure dating by calculating global time-dependent production rates since the Last Glacial Maximum using surface elevations that were corrected and uncorrected for GIA. We find that the magnitude of the GIA effect is spatially and temporally variable. Nuclide production could be reduced by up to 50% in the interior of large ice masses (in North America, Scandinavia and West Antarctica) at times of maximum glacial isostatic depression. Although smaller, the effect is still significant at ice sheet margins, where nuclide production is reduced by >5% and potentially >10%, making exposure ages older in those areas. Away from the ice sheet margins, land surfaces can be isostatically elevated, which can increase nuclide production by >5% and, therefore, make exposure ages younger. Areas that were more recently exposed or that are distal to large ice masses will generally be less affected. Importantly, we find that the effect at the primary 10Be production calibration sites is <1%. Applying a GIA correction to surface-exposure data may help resolve mismatches between some chronologies, but not necessarily in all regions, implying that additional factors may need to be considered. Past atmospheric changes can amplify or reduce the impact of GIA on nuclide production, and the combined effects should be fully accounted for in the future. These time-dependent influences on surface-exposure dating have potentially important implications for interpreting chronologies and for using the data to constrain ice sheet models. • Glacial isostatic adjustment (GIA) can make exposure age estimates older or younger. • Nuclide production can be reduced by up to 50% from isostatic depression. • The GIA effect at the primary 10Be production rate calibration sites is negligible. • Correcting existing exposure datasets can make ages up to ∼2,500 years (15%) older. • Atmospheric changes may amplify or reduce the impact of GIA on exposure ages. [ABSTRACT FROM AUTHOR]

Abstract Recent advances in palaeoecology provide growing evidence of complex spatio-temporal patterns of tree species survival during the last glaciation. The distribution of Sweet chestnut (Castanea sativa Mill.) glacial refugia is still controversial. For this study we built an updated database containing almost all palaeobotanical data on Castanea published to date in the scientific literature and/or stored in the European and African pollen databases (EPD and APD). We used the collected data for assessing the sweet chestnut refugia during the Last Glacial Maximum (LGM). Furthermore, we identify the main changes in the distribution range of the species during the last 200 ka all over Europe. Confirmed chestnut refugia are the Transcausasia, where the species played a prominent role in the forest vegetation, and the Italian and Iberian Peninsulas, where it was restricted to scattered pockets providing favorable habitats. The species may have also survived in the Marmara region and in the Levant, while for the South-Eastern Balkans, north and central France and Northern Africa, the available evidence is too scarce yet for inferring local survival. Mountain ranges and seawater masses played a crucial role in determining the species survival during cold stages. Almost four fifths (79%) of the palaeobotanical sites with pre-cultivation Castanea records were found in the scientific literature, while the remaining 21% was extracted from the EPD and APD. Our study thus shows the growing importance of such curated databases as a key resource for palaeoecological synthesis products, emphasises the relevance of gaining a better spatio-temporal coverage by an extensive review of scientific literature, and underscores the urgent need of gaining new state-of-the art multiproxy records for assessing the causes and consequences of species survival under strongly varying climatic conditions. Highlights • Data are retrieved from the literature (79%) and the European Pollen Database (21%). • There are 856 european palaeobotanical sites with Castanea in pre-cultivation samples. • Transcaucasia, Italy, Iberia, Marmara region and Levant are the five confirmed refugia. • Proximity to mountains and seas was crucial for the survival of the species. • During the early-middle Holocene the species spread naturally from the refugia. [ABSTRACT FROM AUTHOR]

Abstract Constraining glacial history and process on Mt Mansfield, the highest peak in Vermont (1339 m a.s.l.), provides insight into how the Laurentide Ice Sheet shaped the underlying landscape, when latest Pleistocene ice retreated, and how upland and lowland glacial histories relate. Here, we quantify in situ cosmogenic 10Be in 20 bedrock and boulder surfaces, as well as in situ cosmogenic 14C in three of those surfaces, to assess subglacial erosion and exposure history. Isotopic concentrations indicate that Mt. Mansfield's lower elevations (∼400–1200 m a.s.l.) were deeply eroded by at least several meters during the last glaciation and then deglaciated rapidly; 10Be ages across this elevation span are indistinguishable and average 13.9 ± 0.6 ka (n = 15), suggesting that 800 m of ice thinning occurred within at most about a millennium. Conversely, the higher elevations (>1200 m a.s.l.) preserve a more complex geomorphic history. Mt. Mansfield's summit surfaces contain 10Be from previous periods of exposure, indicating that the mountaintop landscapes were likely preserved beneath cold-based, weakly-erosive glacial ice. Exposure ages from the shorter-lived isotope, 14C, are younger (9.7 and 11.7 ka), suggesting that Mt. Mansfield's summit was covered until the early Holocene, perhaps by snowfields, ice carapaces, and/or till. Our findings, in context of previous work, suggest that thinning Laurentide ice flowed through the valleys for at most hundreds of years following deglaciation of the uplands, but that the summit remained shielded by ice or sediment for millennia after the valleys became ice-free. Highlights • We use cosmogenic nuclides to constrain Laurentide Ice Sheet history and behavior. • Mt. Mansfield, the highest point in Vermont, was deglaciated rapidly ∼13.9 ka. • The lower elevations (<1200 m a.s.l.) were deeply eroded by flowing ice. • The summit area was covered by cold-based ice and was minimally eroded. [ABSTRACT FROM AUTHOR]

Abstract Ocean net primary productivity (Npp) is a key component of the marine carbon cycle. Multi-model Npp projections based on a few decades of satellite data show large uncertainties, in particular at low latitudes (30°N−30°S). Calibration of sedimentary proxies with satellite-based Npp estimates allows for the quantitative reconstruction of this variable at longer time-scales. Relative abundance of deep-photic zone coccolithophore species Florisphaera profunda in the fossil record can potentially be used as a quantitative proxy for Npp. However, the robustness of this proxy calibration has been tested in very specific oceanographic settings using surface sediment samples. Here, we use a global dataset of surface sediment (n = 1258) and sediment trap (n = 26) samples with relative abundance data of F. profunda (%) to test the robustness of this proxy as a quantitative indicator of Npp. We study the modern and paleo-ecology of this species and the main factors affecting its latitudinal distribution. Results show that F. profunda % is a strong indicator of Npp at latitudes between 30°N and 30°S, while at higher latitudes temperature-related variables are more important. We develop a global calibration model between satellite Npp estimates and F. profunda for the latitudinal range between 30°N and 30°S, and we apply it to several low-latitude sediment cores with available F. profunda counts covering the Late Glacial Maximum (LGM; 24–19 ka) and the Mid-to-Late Holocene period (MLH; <6 ka). Reconstructed Npp during the LGM is 15% higher than during the MLHdue to the intensification of trade winds that enhanced oceanic upwelling at low latitudes. Highlights • An extensive new modern and fossil global dataset of Florisphaera profunda relative abundances. • F. profunda % show strong correlation to net primary productivity (Npp) only at low latitudes. • Temperature control of F. profunda at high latitudes does not warrant its use as Npp indicator. • F. profunda -Npp calibration allows quantitative reconstruction of past ocean productivity. • Reconstructed Npp at low latitudes is 15% higher during the LGM than the MLH. [ABSTRACT FROM AUTHOR]

Abstract Subglacial hydrology modulates how ice sheets flow, respond to climate, and deliver meltwater, sediment and nutrients to proglacial and marine environments. Here, we investigate the development of subglacial lakes and drainage networks beneath the Fennoscandian and Barents Sea ice sheets over the Late Weichselian. Utilizing an established coupled climate/ice flow model, we calculate high-resolution, spatio-temporal changes in subglacial hydraulic potential from ice sheet build-up (∼37 ka BP) to complete deglaciation (∼10 ka BP). Our analysis predicts up to 3500 potential subglacial lakes, the largest of which was 658 km2, and over 70% of which had surface areas <10 km2, comparable with subglacial lake-size distributions beneath the Antarctic Ice Sheet. Asynchronous evolution of the Fennoscandian Ice Sheet into the flatter relief of northeast Europe affected patterns of subglacial drainage, with up to 100 km3 more water impounded within subglacial lakes during ice build-up compared to retreat. Furthermore, we observe frequent fill/drain cycles within clusters of subglacial lakes at the onset zones and margins of ice streams that would have affected their dynamics. Our results resonate with mapping of large subglacial channel networks indicative of high-discharge meltwater drainage through the Gulf of Bothnia and central Barents Sea. By tracking the migration of meltwater drainage outlets during deglaciation, we constrain locations most susceptible to focussed discharge, including the western continental shelf-break where subglacial sediment delivery led to the development of major trough-mouth fans. Maps of hydraulic potential minima that persist throughout the Late Weichselian reveal potential sites for preserved subglacial lake sediments, thereby defining useful targets for further field-investigation. Highlights • We present modelled subglacial water storage and drainage between 37–10 ka BP. • Up to 3500 potential subglacial lakes predicted during LGM, storing >460 km3 of water. • Subglacial lake clusters are predicted with potential for fill/drain cycles and flood events. • Persistent lakes over the glaciation define potential sites for preserved sediments. • Catchment evolution and drainage outlet migration reveals subglacial discharge foci. [ABSTRACT FROM AUTHOR]

Abstract During the Local Last Glacial Maximum (LLGM), the Northern Apennines hosted more than 100 valley and mountain glaciers covering collectively more than 260 km2. Cosmogenic 10Be exposure ages obtained for the first time along the Apenninic range constrain the age of the LLGM to pre-date ca 21 ka. The estimated volumes of these Late Pleistocene glaciers exceeded 9.1 km3 w.e. Their reconstructed Equilibrium Line Altitudes (ELAs) range from ca. 1200 m a.s.l. for northerly facing compound basin valley glaciers to ca. 1620 m a.s.l. for southerly facing mountain glaciers. Reconstructed ELAs in the western sector of the Northern Apennines were among the lowest recorded for the whole of the Italian peninsula, including the Alps, and also when compared with other mountain chains in the surrounding Mediterranean basin. These probably reflect exceptionally high accumulation rates fed by storm tracks in the western Mediterranean, which in turn has implications for the atmospheric circulation pattern that prevailed in the region at the time. [ABSTRACT FROM AUTHOR]

Numerous cases of timing differences between glacier advances recorded in mountain environments have been documented over the last decade, usually suggesting potential age conflicts between the different dating techniques. The frequent use of a single technique to date numerically a given glacial sequence makes it difficult to address to what extent age differences can be an artifact related to biased numerical age results or a paleoclimate signature. Here we present a new set of 43 numerical ages based on three dating techniques — 10 Be surface exposure dating; radiocarbon; and optically stimulated luminescence— that complement the chronology of Pleistocene glacial advances in the Porma valley, in the central Cantabrian Mountains of Spain. Results compliment previous chronologies in the area, supporting an important glacial advance during Marine Isotope Stage 3 (Stage IIa: ∼56 ka) that culminated with the Last Glacial Maximum advance (Stage IIb: ∼33–24 ka) of MIS 2 in response to increased rainfall and solar insolation minima. Glacier fronts reached elevations as low as 1130 m a.s.l. possibly without overriding evidence related to the previous Pleistocene glacial maximum extent. Glacier recession in the Cantabrian Mountains started at 21–20 ka ago, after the global LGM. We suggest that the recession was initiated by increased insolation followed by hyper-cool and dry conditions during Heinrich Stadial 1 in response to meltwater discharges in the North Atlantic. [ABSTRACT FROM AUTHOR]

This paper reconstructs the deglaciation of the Laurentide Ice Sheet (LIS; including the Innuitian Ice Sheet) from the Last Glacial Maximum (LGM), with a particular focus on the spatial and temporal variations in ice streaming and the associated changes in flow patterns and ice divides. We build on a recent inventory of Laurentide ice streams and use an existing ice margin chronology to produce the first detailed transient reconstruction of the ice stream drainage network in the LIS, which we depict in a series of palaeogeographic maps. Results show that the drainage network at the LGM was similar to modern-day Antarctica. The majority of the ice streams were marine terminating and topographically-controlled and many of these continued to function late into the deglaciation, until the ice sheet lost its marine margin. Ice streams with a terrestrial ice margin in the west and south were more transient and ice flow directions changed with the build-up, peak-phase and collapse of the Cordilleran-Laurentide ice saddle. The south-eastern marine margin in Atlantic Canada started to retreat relatively early and some of the ice streams in this region switched off at or shortly after the LGM. In contrast, the ice streams draining towards the north-western and north-eastern marine margins in the Beaufort Sea and in Baffin Bay appear to have remained stable throughout most of the Late Glacial, and some of them continued to function until after the Younger Dryas (YD). The YD influenced the dynamics of the deglaciation, but there remains uncertainty about the response of the ice sheet in several sectors. We tentatively ascribe the switching-on of some major ice streams during this period (e.g. M'Clintock Channel Ice Stream at the north-west margin), but for other large ice streams whose timing partially overlaps with the YD, the drivers are less clear and ice-dynamical processes, rather than effects of climate and surface mass balance are viewed as more likely drivers. Retreat rates markedly increased after the YD and the ice sheet became limited to the Canadian Shield. This hard-bed substrate brought a change in the character of ice streaming, which became less frequent but generated much broader terrestrial ice streams. The final collapse of the ice sheet saw a series of small ephemeral ice streams that resulted from the rapidly changing ice sheet geometry in and around Hudson Bay. Our reconstruction indicates that the LIS underwent a transition from a topographically-controlled ice drainage network at the LGM to an ice drainage network characterised by less frequent, broad ice streams during the later stages of deglaciation. These deglacial ice streams are mostly interpreted as a reaction to localised ice-dynamical forcing (flotation and calving of the ice front in glacial lakes and transgressing sea; basal de-coupling due to large amount of meltwater reaching the bed, debuttressing due to rapid changes in ice sheet geometry) rather than as conveyors of excess mass from the accumulation area of the ice sheet. At an ice sheet scale, the ice stream drainage network became less widespread and less efficient with the decreasing size of the deglaciating ice sheet, the final elimination of which was mostly driven by surface melt. [ABSTRACT FROM AUTHOR]

We measured meteoric 10 Be variation throughout a marine sediment core from the Larsen B embayment (LBE) of the Antarctic Peninsula, and collected in situ 10 Be and 14 C exposure ages on terrestrial glacial deposits from the northern and southern margins of the LBE. We use these data to reconstruct Last Glacial Maximum (LGM) to present deglaciation and ice shelf change in the LBE. Core sedimentary facies and meteoric 10 Be data show a monotonic progression from subglacial deposits to sub-ice-shelf deposits to open-marine conditions, indicating that its collapse in 2002 was unprecedented since the LGM. Exposure-age data from the southern LBE indicate 40 m of ice surface lowering between 14 and 6 ka, then little change between 6 ka and the 2002 collapse. Exposure-age data from the northern LBE show a bimodal distribution in which clusters of apparent exposure ages in the ranges 4.9–5.1 ka and 1.0–2.0 ka coexist near 50 m elevation. Based on these results, other published terrestrial and marine deglaciation ages, and a compilation of sea bed imagery, we suggest a north-to-south progression of deglaciation in the northeast Antarctic Peninsula in response to Holocene atmospheric and oceanic warming. We argue that local topography and ice configuration inherited from the LGM, in addition to climate change, are important in controlling the deglaciation history in this region. [ABSTRACT FROM AUTHOR]

The Magdalen Islands (Québec, Canada) in the centre of the Gulf of St. Lawrence are located in a strategic position for providing an overview of the relative sea-level (RSL) history of the Maritime Provinces of eastern Canada. Although data are available for the coastal terrestrial areas of the Maritimes, data from the Gulf are very scarce and both the RSL and glacio-isostatic adjustment (GIA) models extrapolate for this central region. This study provides new stratigraphic and chronological data from four outcrops and two coring sites on the Magdalen Islands. In addition to the five samples used mainly for age control purposes, nine new luminescence ages are presented. With these new data added to the available literature, a new RSL curve is reconstructed for the LGM to the late Holocene period and a partial curve is proposed for the interval between the late MIS 4 to the MIS 3. Data also indicate a few insights for the MIS 5 period. Results reveal that for the LGM to the late Holocene, the curve corresponds to the J-shaped curve scenario recognized in the literature. The RSL changes during this period are the result of glacio-isostatic rebound, migration and collapse of the peripheral forebulge, and eustatic sea-level changes. For the LGM to the early Holocene, glacio-isostatic depression curves displaying a few local differences are also proposed. For the late Holocene, the data constrain the curve between two types of indicators, i.e. marine and terrestrial, and indicate that the RSL has risen at least 3 m during the last two millennia. Sediments dated to the MIS 5 and the interval between the late MIS 4 and the MIS 3 illustrate that the GIA following the LGM also occurred for the MIS 5 interglacial and the MIS 3 interstadial. Finally, recent GIA models are discussed in light of the results of this paper. [ABSTRACT FROM AUTHOR]

A canopy-scale model (CANOAK) was used to simulate lowland Amazonia during the Last Glacial Maximum. Modeled values of Net Ecosystem Exchange driven by glacial environmental conditions were roughly half the magnitude of modern fluxes. Factorial experiments reveal lowered [CO 2 ] to be the primary cause of reduced carbon fluxes while lowered air temperatures enhance net carbon uptake. LGM temperatures are suggested to be closer to optimal for carbon uptake than modern temperatures, explained through the canopy energy balance. Further analysis of the canopy energy balance and resultant leaf temperature regime provide viable mechanisms to explain enhanced carbon-water relations at lowered temperatures and forest robustness over glaciations. An ecophysiological phenomena known as the ‘cross-over’ point, wherein leaf temperatures sink below air temperature, was reproduced and found to demarcate critical changes in energy balance partitioning. [ABSTRACT FROM AUTHOR]

Milankovitch orbital parameters control cycles of insolation, a primary pacer of long term changes in climate, but exactly how insolation signals are transmitted around the globe in the climate system is unclear. In order to address the fundamental questions of when and how ice age climates begin and end, how fast glaciers retreated during the last deglaciation, and how glaciers behaved before anthropogenic influence, we need robust glacial chronologies. The timing of local glacial maxima beyond the last glacial cycle, however, has remained largely unconstrained due to moraine degradation over time, limiting our ability to fully explore these questions. By developing a detailed geomorphic surficial map and targeting relatively tall, ridge-top boulders, we have constructed a new, precise 10Be chronology of glacial maxima of the Ñirehuao glacier lobe (45°S) for the last two glacial cycles. We report one of the first directly dated records of a MIS 6 glacier advance in Patagonia, which formed a major set of moraines by at least 153 ± 5.1 ka, with a stillstand or smaller readvance by 137 ± 4.2 ka, corresponding to the two coldest and dustiest periods of MIS 6 in Antarctica. The next largest advance occurred at 23.6 ± 0.9 ka, at the end of peak Southern Hemisphere MIS 2 cooling. Retreat of the glacier commenced by ∼18.5 cal ka BP when lakes in a tributary valley just to the southwest became ice-free. Overall we find that advances of the Ñirehuao glacier lobe occur when winter sea ice around Antarctica is expansive and both obliquity and eccentricity are at their minima. • We present a new, detailed geomorphic map and 10Be chronology of the Ñirehuao glacier lobe for the last two glacial cycles • We report one of the first directly dated records of a MIS 6 glacier advance in Patagonia • The Ñirehuao glacier lobe formed a major set of moraines by 153±5.1 ka with a stillstand or smaller readvance by 137±4.2 ka • The MIS 2 glacial maximum occurred at 23.6±0.9 ka and subsequent retreat of the glacier commenced by ∼18.5 cal ka BP • Overall, advances occurred when winter sea ice around Antarctica was expansive and obliquity and eccentricity were at minima [ABSTRACT FROM AUTHOR]

Exposure of the presently submerged continental shelf of Southeast Asia during low sea-level stands of the Quaternary is thought to be deeply involved in the biogeographic evolution of this biodiversity hotspot. Inland proxy records are mounting to argue grassland expansions over Southeast Asia during glacial periods, lending supports to the existence of a transequatorial "savanna corridor" as hypothesized. However, pollen records retrieved from marine sediments have indicated widespread rainforests on the exposed northern Sunda Shelf. To reconcile these seemingly conflicting observations, here we present new, multisite marine pollen records from the southern South China Sea focusing on the Last Glacial Maximum (LGM) time interval. It is found that the sites in front of the Sunda Shelf palaeo-rivers contain substantially more Poaceae pollen, in particular a smaller size fraction, than the site offshore North Borneo. Among the sites, abundant lowland tree pollen with similar major taxa is also observed. The co-occurrence of grass and rainforest pollen suggests a longitudinal climate gradient with increasing aridity toward the interior of glacial Sundaland. Combining our results with various palynological evidence from marine sediments seems to indicate that the vegetation on the exposed Sunda Shelf might not be fully recognized by previous studies. This is likely due to an admixture of pollen from other source regions, particularly Borneo where the rainforest was retained during glacial periods. Therefore, the extant vegetation records, from both terrestrial and marine archives, support the hypothesis of a "savanna corridor" over the LGM sundaland. • The LGM pollen records show spatial discrepancy in the southern South China Sea. • New marine sites suggest that the vegetation over the exposed Sunda Shelf included both savanna and rainforest. • The existing evidences support the presence of a savanna corridor over the Sundaland. • Poaceae pollen size distinguishes various vegetation types of Southeast Asia. [ABSTRACT FROM AUTHOR]

Evidence of widespread alpine glaciations during the Late Pleistocene in mid-latitudes has long attracted attention of researchers. However, there were no studies that contain absolute ages in the Lesser Caucasus despite the fact that it is one of the major glaciated regions in Eurasia. Here, we present first cosmogenic 36 Cl surface exposure ages from the Karçal Mountains (41.24° N, 42.06° E, 3431 m a.s.l., above sea level) which is located in the most western part of the Lesser Caucasus in the northeastern Anatolia. In the Karçal Mountains, there are numerous valleys that have experienced significant glaciations since Late Pleistocene. We have investigated one of the largest valleys, the east-facing Karçal Valley, that hosts even a small (2926 m a.s.l.) recent glacier located at above 3000 m a.s.l. Fossil and recent rock glaciers along with lateral and recessional moraines exist in the valley. We conducted the study in two stages. First, we mapped the geomorphological units in the Karçal Valley in detail based on our field works and aerial photography. Later, we collected 10 rock samples from the fossil rock glacier and recessional moraines for cosmogenic 36 Cl surface exposure dating. The results outline a glacial chronology that is typical of the Last Glacial Maximum. Although the maximum extent and timing of the glaciation is not exactly known as lateral and terminal moraines were not suitable for sampling, recessional moraines indicate that the Karçal Valley palaeoglacier deglaciation started at least 19.9 ± 1.2 ka ago. Fossil rock glacier samples were dated to 15.7 ± 1.3 ka. These quantitative results are first in the Lesser Caucasus and compatible with previous ages obtained from other valleys in the nearby Eastern Black Sea region, Anatolian and some of the European Mountains. [ABSTRACT FROM AUTHOR]

Southern South America contains a glacial geomorphological record that spans the past million years and has the potential to provide palaeoclimate information for several glacial periods in Earth's history. In central Patagonia, two major outlet glaciers of the former Patagonian Ice Sheet carved deep basins ∼50 km wide and extending over 100 km into the Andean plain east of the mountain front. A succession of nested glacial moraines offers the possibility of determining when the ice lobes advanced and whether such advances occurred synchronously. The existing chronology, which was obtained using different methods in each valley, indicates the penultimate moraines differ in age by a full glacial cycle. Here, we test this hypothesis further using a uniform methodology that combines cosmogenic nuclide ages from moraine boulders, moraine cobbles and outwash cobbles. 10 Be concentrations in eighteen outwash cobbles from the Moreno outwash terrace in the Lago Buenos Aires valley yield surface exposure ages of 169–269 ka. We find 10 Be inheritance is low and therefore use the oldest surface cobbles to date the deposit at 260–270 ka, which is indistinguishable from the age obtained in the neighbouring Lago Pueyrredón valley. This suggests a regionally significant glaciation during Marine Isotope Stage 8, and broad interhemispheric synchrony of glacial maxima during the mid to late Pleistocene. Finally, we find the dated outwash terrace is 70–100 ka older than the associated moraines. On the basis of geomorphological observations, we suggest this difference can be explained by exhumation of moraine boulders. [ABSTRACT FROM AUTHOR]

Cosmogenic 10 Be surface-exposure dating and numerical glacier modeling are used to reconstruct glacial chronology and climate in the Colorado Sangre de Cristo Mountains during the local last glacial maximum (LLGM) and the subsequent deglaciation. Twenty-two surface-exposure ages on moraine boulders and polished-bedrock outcrops in the Willow Creek valley and ten in two adjacent valleys indicate that glaciers were at or near their maxima from ∼21 ka until 17–16 ka, and then retreated rapidly, nearly deglaciating the Willow Creek valley entirely by ∼14 ka. Coupled energy/mass-balance and flow modeling of two of the glaciers indicates that, if changing ice extent was driven only by temperature and insolation changes, temperature depressions of 5.0 and 5.1 °C from modern conditions, with an uncertainty of approximately + 1.5 / − 1.0 °C, would have sustained the glaciers in mass-balance equilibrium at their LLGM extents. Doubling or halving of modern precipitation during the LLGM would have been associated with 2.7–3.0 °C and 6.9–7.0 °C temperature depression respectively. Approximately half of the subsequent LLGM–to-modern climate change was accomplished by ∼14 ka. If the rapid main phase of deglaciation between about 16 ka and 14 ka was driven solely by temperature and insolation changes, it would have been associated with a temperature rise of about 2.5 °C, at a mean rate of approximately 1.1 °C/ky. This new chronology of the last glaciation is generally consistent with others developed recently in the Colorado Rocky Mountains. The numerical modeling, however, suggests a lesser LLGM temperature depression from modern conditions than have most previous studies in Colorado. [ABSTRACT FROM AUTHOR]

Detailed bathymetric and sub-bottom acoustic observations in Bourgeois Fjord (Marguerite Bay, Antarctic Peninsula) provide evidence on sedimentary processes and glacier dynamics during the last glacial cycle. Submarine landforms observed in the 50 km-long fjord, from the margins of modern tidewater glaciers to the now ice-distal Marguerite Bay, are described and interpreted. The landforms are grouped into four morpho-sedimentary systems: (i) glacial advance and full-glacial; (ii) subglacial and ice-marginal meltwater; (iii) glacial retreat and neoglaciation; and (iv) Holocene mass-wasting. These morpho-sedimentary systems have been integrated with morphological studies of the Marguerite Bay continental shelf and analysed in terms of the specific sedimentary processes and/or stages of the glacial cycle. They demonstrate the action of an ice-sheet outlet glacier that produced drumlins and crag-and-tail features in the main and outer fjord. Meltwater processes eroded bedrock channels and ponds infilled by fine-grained sediments. Following the last deglaciation of the fjord at about 9000 yr BP, subsequent Holocene neoglacial activity involved minor readvances of a tidewater glacier terminus in Blind Bay. Recent stillstands and/or minor readvances are inferred from the presence of a major transverse moraine that indicates grounded ice stabilization, probably during the Little Ice Age, and a series of smaller landforms that reveal intermittent minor readvances. Mass-wasting processes also affected the walls of the fjord and produced scars and fan-shaped deposits during the Holocene. Glacier-terminus changes during the last six decades, derived from satellite images and aerial photographs, reveal variable behaviour of adjacent tidewater glaciers. The smaller glaciers show the most marked recent retreat, influenced by regional physiography and catchment-area size. [ABSTRACT FROM AUTHOR]

A recent data campaign in the East Siberian Sea has revealed evidence of grounded and floating ice dynamics in regions of up to 1000 m water depth, and which are attributed to glaciations older than the Last Glacial Maximum (21 kyrs BP). The main hypothesis based on this evidence is that a small ice cap developed over Beringia and expanded over the East Siberian continental margin during some of the Late Pleistocene glaciations. Other similar evidence of ice dynamics that have been previously collected on the shallow continental shelves of the Arctic Ocean have been attributed to the penultimate glaciation, i.e. Marine Isotopes Stage 6 (≈140 kyrs BP). We use an ice sheet model, forced by two previously simulated MIS 6 glacial maximum climates, to carry out a series of sensitivity experiments testing the impact of dynamics and mass-balance related parameters on the geometry of the East Siberian ice cap and ice shelf. Results show that the ice cap developing over Beringia connects to the Eurasian ice sheet in all simulations and that its volume ranges between 6 and 14 m SLE, depending on the climate forcing. This ice cap generates an ice shelf of dimensions comparable with or larger than the present-day Ross ice shelf in West Antarctica. Although the ice shelf extent strongly depends on the ice flux through the grounding line, it is particularly sensitive to the choice of the calving and basal melting parameters. Finally, inhibiting a merging of the Beringia ice cap with the Eurasian ice sheet affects the expansion of the ice shelf only in the simulations where the ice cap fluxes are not large enough to compensate for the fluxes coming from the Eurasian ice sheet. [ABSTRACT FROM AUTHOR]

South Georgia, one of the largest sub-Antarctic islands, is located within the Southern Ocean and is influenced by the moisture-supplying Southern Westerlies and the Antarctic Circumpolar Current, which are highly susceptible to Southern Hemisphere climate variability. Its unique location causes South Georgia's remaining ice masses to react sensitively to climate change, resulting in highly dynamic ice cap waxing and waning, as well as in geomorphological and sedimentological changes on the island and its continental shelf. Sediments around the island have been archiving this ice cap behaviour since at least the Last Glacial Maximum (LGM) and are therefore an important target to investigate past ice cap evolution and climate. Despite several interdisciplinary studies on land and in coastal areas, much of the glacial history is still poorly constrained due to a lack of offshore data. This study presents the, thus far, most distal marine sediment succession from outer Drygalski Trough on the mid-continental shelf of South Georgia. Composite multi-proxy-analyses, together with radiocarbon dating, sub-bottom profiler and high-resolution bathymetric data provide first insights into the evolution of a large glacial trough south of South Georgia since the LGM. Several moraines close to the shelf edge indicate shelf-wide glaciation during the local LGM, which, based on extrapolation of the oldest reliable radiocarbon date, occurred before 30 ka BP at the earliest. Basal stratified diamicton at the core site was interpreted as waterlain till deposited in a subglacial cavity with restricted seawater access and suggests grounding zone-proximal sedimentation in the early phases of deglaciation. The ice margin remained stable until ∼17.5 cal ka BP, when ice quickly retreated from the mid-continental shelf and sedimentation at the core site was dominated by hemipelagic suspension settling with some iceberg melting. Further retreat was interrupted by a local ice readvance and associated increased hinterland erosion during the Antarctic Cold Reversal (14.5–12.8 ka), as indicated by peak sedimentation rates (>190 cm ka−1) between 13.4 and 12.4 cal ka BP. In contrast, the continuous deposition of ice-distal to open-marine mud at rates of only ∼30 cm ka−1 throughout the Holocene indicate that any other LGM-subsequent glacier readvances reached significantly lesser extents and were probably confined to the fjord. Our data provide new evidence in support of a shelf-wide glaciation during the LGM and suggest rapid, but stepwise ice retreat during deglaciation. • Waterlain till proves ice-proximal sedimentation on the mid-continental shelf. • South Georgia ice cap extended to the shelf edge, likely during the LGM. • Glacial landforms show extensive ice streaming and intermittent retreat. • Peak shelf sedimentation rates imply enhanced terrestrial erosion during the ACR. • Ice-distal to open-marine conditions prevailed throughout the Holocene. [ABSTRACT FROM AUTHOR]

Reconstructing the advance and retreat of past ice sheets provides important long-term context for recent change(s) and enables us to better understand ice sheet responses to forcing mechanisms and external boundary conditions that regulate grounding line retreat. This study applies various radiocarbon dating techniques, guided by a detailed sedimentological analyses, to reconstruct the glacial history of Anvers-Hugo Trough (AHT), one of the largest bathymetric troughs on the western Antarctic Peninsula (WAP) shelf. Existing records from AHT indicate that the expanded Antarctic Peninsula Ice Sheet (APIS) advanced to, or close to, the continental shelf edge during the Last Glacial Maximum (LGM; 23-19 cal kyr BP [ = calibrated kiloyears before present]), with deglaciation of the outer shelf after ∼16.3 cal kyr BP. Our new chronological data show that the APIS had retreated to the middle shelf by ∼15.7 cal kyr BP. Over this 600-year interval, two large grounding-zone wedges (GZW) were deposited across the middle (GZW2) and inner shelf (GZW3), suggesting that their formation occurred on centennial rather than millennial timescales. Expanded sequences of sub-ice shelf sediments occur seaward of the inner GZW3, which suggests that the grounding line remained stationary for a prolonged period over the middle shelf. Grounding-line retreat rates indicate faster retreat across the outer to middle shelf compared to retreat across the middle to inner shelf. We suggest that variable retreat rates relate to the broad-scale morphology of the trough, which is characterised by a relatively smooth, retrograde seabed on the outer to middle shelf and rugged morphology with a locally landward shallowing bed and deep basin on the inner shelf. A slowdown in retreat rate could also have been promoted by convergent ice flow over the inner shelf and the availability of pinning points associated with bathymetric highs around Anvers Island and Hugo Island. • The deglacial history of Anvers-Hugo Trough is revealed by marine geological and geophysical data. • Application of multiple 14C dating methods allows reliable dating of ice sheet retreat. • Grounded ice had retreated to the mid-shelf by ∼15.7 cal kyr BP. • Retreat rates are controlled by the broad-scale morphology of the shelf. [ABSTRACT FROM AUTHOR]

Numerous studies have documented the sedimentary sequences of the Yangtze Delta in response to relative sea-level changes since the Last Glacial Maximum (LGM). However, the pre-LGM sedimentary history of the paleo-Yangtze Delta remains unknown, especially for the formation timing of the basal fluvial sedimentary succession in the paleo-Yangtze incised valley. Here, based on luminescence dating techniques, the sedimentary stratigraphy of three sediment cores (YD016, YD014 and YD006) were constrained and the sedimentary successions were analyzed. Combining with previously published sedimentary sequences, we infer spatiotemporal variation of the stratigraphic architectures over the Yangtze Delta through the time spanning from the late Pleistocene to the Holocene (∼50–0 ka). Our reconstruction for the paleogeography and environmental evolution of the paleo-Yangtze incised valley showed that the basal fluvial channel belts in the paleovalley associated with coeval laterally extensive paleosol-bearing stratigraphy at the interfluves occurred in the transition between marine isotope stage (MIS) 3 and MIS 2; the overlying sedimentary successions are characterized by the post-glacial floodplain deposits formed between 19 and 12 ka, and estuary to shallow marine deposits during early Holocene (11–8 ka); and then the upper most is the Yangtze Delta depositional systems dated to mid-to-late Holocene (since ∼8 ka). Correlations of the chronostratigraphy of sediment cores over the cross-sections in this region suggest that a superimposed compound fluvial channel complex has probably characterized the paleo-Yangtze incised valley systems since MIS 3. Apart from the post-LGM infilling of the LGM incised valley, the basal MIS 3 fluvial deposits might represent the earlier infilling over another incised valley, which might be formed during MIS 4 although our cores have not reached yet. Such hierarchical incised valley systems in the paleo-Yangtze Delta were likely related to the late Quaternary sea-level changes. In addition, the relict inherited topography since the last glacial period could have played an important role in the stacking patterns of the paleo-Yangtze incised valleys. • Luminescence ages constrained the basal fluvial deposits of the Yangtze incised valley in MIS3/2 • The paleo-Yangtze incised-valley complex might be existed in MIS 3 and lasted until to MIS 2 • A superimposed compound fill pattern probably have occurred in the Yangtze valley since MIS 3. • The hierarchical incised valley systems and inherited topography should be considered for the paleo-Yangtze Delta evolution. [ABSTRACT FROM AUTHOR]

Reconstructions of the extent and height of the Irish Ice Sheet (IIS) during the Last Glacial Maximum (LGM, ∼19–26 ka) are widely debated, in large part due to limited age constraints on former ice margins and due to uncertainties in the origin of the trimlines. A key area is southwestern Ireland, where various LGM reconstructions range from complete coverage by a contiguous IIS that extends to the continental shelf edge to a separate, more restricted southern-sourced Kerry-Cork Ice Cap (KCIC). We present new 10 Be surface exposure ages from two moraines in a cirque basin in the Macgillycuddy's Reeks that provide a unique and unequivocal constraint on ice thickness for this region. Nine 10 Be ages from an outer moraine yield a mean age of 24.5 ± 1.4 ka while six ages from an inner moraine yield a mean age of 20.4 ± 1.2 ka. These ages show that the northern flanks of the Macgillycuddy's Reeks were not covered by the IIS or a KCIC since at least 24.5 ± 1.4 ka. If there was more extensive ice coverage over the Macgillycuddy's Reeks during the LGM, it occurred prior to our oldest ages. [ABSTRACT FROM AUTHOR]

Successively smaller glacial extents have been proposed for continental Eurasia during the stadials of the last glacial period leading up to the Last Glacial Maximum (LGM). At the same time the large mountainous region east of Lake Baikal, Transbaikalia, has remained unexplored in terms of glacial chronology despite clear geomorphological evidence of substantial past glaciations. We have applied cosmogenic 10 Be exposure dating and optically stimulated luminescence to establish the first quantitative glacial chronology for this region. Based on eighteen exposure ages from five moraine complexes, we propose that large mountain ice fields existed in the Kodar and Udokan mountains during Oxygen Isotope Stage 2, commensurate with the global LGM. These ice fields fed valley glaciers (>100 km in length) reaching down to the Chara Depression between the Kodar and Udokan mountains and to the valley of the Vitim River northwest of the Kodar Mountains. Two of the investigated moraines date to the Late Glacial, but indications of incomplete exposure among some of the sampled boulders obscure the specific details of the post-LGM glacial history. In addition to the LGM ice fields in the highest mountains of Transbaikalia, we report geomorphological evidence of a much more extensive, ice-cap type glaciation at a time that is yet to be firmly resolved. [ABSTRACT FROM AUTHOR]

The spatiotemporal pattern of glaciation along the Andes Mountains is an important proxy record reflecting the varying influence of global and regional circulation features on South American climate. However, the timing and extent of glaciation in key parts of the orogen, particularly the deglaciated arid Andes, are poorly constrained. We present new cosmogenic 10 Be and 36 Cl exposure ages for glacial features on and near the Chajnantor Plateau (23 °S). The new dates, although scattered due to cosmogenic inheritance, imply that the most recent extensive glacial occupation ended before or during the global Last Glacial Maximum (LGM). We discuss this new record in the context of published glacial chronologies from glacial features in Peru, Bolivia, and northern Chile rescaled using the latest cosmogenic 10 Be production rate calibration for the tropical Andes. The results imply regionally synchronous moraine stabilization ca. 25–40 ka, 15–17 ka, and 12–14 ka, with the youngest of these moraines absent in records south of ∼20 °S, including in our new Chajnantor area chronology. This spatial pattern implicates easterly moisture in generating sufficient snowfall to glaciate the driest parts of the Andes, while allowing a role for westerly moisture, possibly modulated by the migration of the Southern Westerly Wind belt, in the regions near and south of the Atacama Desert. [ABSTRACT FROM AUTHOR]

Stable isotope analysis of plant waxes (δ13C wax and δD wax) along with detailed pollen data provide a new perspective on vegetation and precipitation variability in Serra Sul de Carajás, southeastern (SE) Amazonia, over the past ∼25 cal kyr BP. The δD wax record indicates drier conditions during the Last Glacial Maximum (LGM) and a transition to wetter conditions into the Holocene, while the δ13C wax data reveal that vegetation did not experienced C 3 /C 4 shifts and remained dominated by C 3 -plant communities. Under glacial conditions C 3 -savanna was prominent on the Serra Sul plateau with tropical forest areas limited to the lower slopes. Tropical forests expanded upslope and forest patches developed on the plateau as a response to more humid and warmer conditions during the Holocene. Pollen data indicate a shift towards more open landscape of savanna, woodlands, and open forests during the mid-Holocene. The δD wax record exhibits a distinct moisture variability during the Holocene, not always coherent with the vegetation data (pollen), especially during the mid-Holocene interval. Our study confirms the complexity and the overall lack of coherence among Holocene moisture proxy records throughout the monsoon domain in South America and suggest that Holocene local moisture conditions might not follow the regional monsoonal variability. Our data further stress the need for more multi-proxy reconstructions of hydroclimate patterns in SE Amazonia. • C 3 -plant communities are dominant in Serra Sul de Carajás. • Formation of no-modern-analog community during the glacial period. • Hydroclimate heterogeneities in eastern Amazonia. [ABSTRACT FROM AUTHOR]

Paleoglacial reconstructions in the European Alps have mainly focused on specific climatic periods such as the Last Glacial Maximum (LGM) or the Younger Dryas, with few studies investigating post-LGM Alpine glacier fluctuations encompassing broader temporal periods. In this study, we present a detailed reconstruction of the post-LGM glacial history of the Dora Baltea catchment, which hosted one of the main Quaternary glacial systems of the western European Alps. By combining existing and new chronological constraints from glacial and postglacial landforms/deposits into 2D and 3D ice surface reconstructions, we quantitatively reproduce the timing and ice-configuration of six LGM to early Holocene paleoglacial stages. Our deglaciation sequence along the Dora Baltea valley can be correlated with specific Lateglacial to Holocene paleoclimatic periods, in line with post-LGM glacier reconstructions from other Alpine areas. We estimated paleo equilibrium-line altitudes (ELAs) for each ice stage, using empirical ice-geometric methods. Our results indicate a low ELA sensitivity to ice decay during the early stages of deglaciation, despite significant glacier retreat from the piedmont into the massifs, suggesting a major role of catchment topography in controlling ELA estimates of large glacial systems. Finally, we provide chronological constraints for two major valley-slope collapse events, both postdating the Dora Baltea glacier withdrawal but implying different landscape response time to deglaciation as well as different triggering factors. [ABSTRACT FROM AUTHOR]

We report the presence of Late Pleistocene piedmont glaciers represented by the largest hummocky moraine field observed in the Eastern Mediterranean. The piedmont glaciers originated from the Geyikdağ ice cap (∼40 km 2 ), situated between 2350 and 2650 m above sea level (a.s.l.) (Central Tauride Mountains of Turkey), and deeply carved the north-facing hillslopes before reaching the Namaras Valley (2000–2050 m a.s.l). The hummocky moraines resulted from in-situ deposition of stagnant glacier ice where debris cover was heterogeneously distributed on the glacier surface. Thirty-four boulders from hummocky, disintegration, lateral and terminal moraines from the Namaras Valley and the tributary Susam Valley (2100–2200 m a.s.l.) were dated by cosmogenic 36 Cl surface exposure dating. The moraine ages indicate three phases of deglaciation during the Late Pleistocene. The oldest deglaciation occurred in the Namaras Valley at 18.0 ± 1.1 ka (ka: thousand years ago) towards the end of the Last Glacial Maximum (LGM) and is recorded entirely by hummocky moraines. We speculate that hummocky moraine forming processes with cycles of relief inversion gave rise to boulder apparent ages up to a few thousand years younger in our study area. Therefore, 18.0 ± 1.1 ka should be regarded as a minimum age with a probable true age much closer to the local-LGM values (∼20 ka) as observed in the surrounding mountains. Paleo-piedmont glaciers also deposited several lateral moraines that are ∼50 m higher than the hummocky moraines. Although the lateral moraines probably represent the build-up and the hummocky moraines the final phase of the same local-LGM-pulse, both lateral moraines started to retreat from the Late-glacial (14.0 ± 2.7 ka) and gradually disappeared by mid-Holocene (5.2 ± 1.0 ka), encompassing the Younger Dryas (YD) stadial. In the Susam Valley, the Late-glacial is represented by a terminal moraine (13.4 ± 1.5 ka). The glacier retreat was very fast as indicated by an almost instantaneous disappearance of 5 km long Susam Valley glacier, represented by disintegration and hummocky moraines (14.0 ± 1.3 ka). Alternatively, in case the oldest boulder age is taken into account, the Susam Valley glacier can be also attributed to the late LGM (∼17 ka) to Late-glacial (∼14 ka) transition. Near the exit of the Susam Valley a right lateral moraine was deposited 11.6 ± 1.3 ka ago, confirming the presence of the YD in Geyikdağ. Comparable glacial chronologies were obtained from other Turkish and Mediterranean mountains. [ABSTRACT FROM AUTHOR]

Our study in the Başyayla Valley in northeastern Anatolia showed evidence of four glacier advances that built terminal and lateral moraines. Surface exposure dating of boulders on these moraines showed that the Maximum Ice Extent (MIE) was asynchronous with the global Last Glacial Maximum (LGM; 22.1 ± 4.3 thousand years; ka). The local MIE took place at least 57.0 ± 3.5 ka ago. The extent of the Başyayla Glacier during this advance is not known exactly because the boulders are only preserved on a lateral moraine. The next advance was prior to 41.5 ± 2.5 ka, and it descended down the valley to approximately 2320 m above sea level (m a.s.l.), with a glacier length of 5.3 km. During the early global LGM, the Başyayla Glacier extended for a distance of 4.9 km down to approx. 2430 m a.s.l. The last recorded advance occurred during the global LGM. This extension was 0.7 km smaller than the local MIE and its terminus reached 2490 m a.s.l. only. The exposure ages of boulders in a retreat position at an altitude of approx. 3045 m a.s.l. indicate that the valley has remained ice-free since the Lateglacial period. Therefore, the Lateglacial extent was limited to the cirque system in the uppermost part of the catchment. Furthermore, Holocene glacier oscillations seem to be either absent or restricted to solifluction in the whole catchment and to rock glacier movements in the southern tributary of the Başyayla Valley system. [ABSTRACT FROM AUTHOR]

Post-glacial sea level dynamics during the last 15,000 calendar years are highly variable along the Pacific coast of Canada. During the Last Glacial Maximum, the Earth's crust was depressed by ice loading along the mainland inner coast and relative sea levels were as much as 200 m higher than today. In contrast, some outer coastal areas experienced a glacial forebulge (uplift) effect that caused relative sea levels to drop to as much as 150 m below present levels. Between these inner and outer coasts, we hypothesize that there would have been an area where sea level remained relatively stable, despite regional and global trends in sea level change. To address this hypothesis, we use pond basin coring, diatom analysis, archaeological site testing, sedimentary exposure sampling, and radiocarbon dating to construct sea level histories for the Hakai Passage region. Our data include 106 newly reported radiocarbon ages from key coastal sites that together support the thesis that this area has experienced a relatively stable sea level over the last 15,000 calendar years. These findings are significant in that they indicate a relatively stable coastal environment amenable to long-term human occupation and settlement of the area. Our results will help inform future archaeological investigations in the region. [ABSTRACT FROM AUTHOR]

Sea-level history since the Last Glacial Maximum on the Pacific margin of North America is complex and heterogeneous owing to regional differences in crustal deformation (neotectonics), changes in global ocean volumes (eustasy) and the depression and rebound of the Earth's crust in response to ice sheets on land (isostasy). At the Last Glacial Maximum, the Cordilleran Ice Sheet depressed the crust over which it formed and created a raised forebulge along peripheral areas offshore. This, combined with different tectonic settings along the coast, resulted in divergent relative sea-level responses during the Holocene. For example, sea level was up to 200 m higher than present in the lower Fraser Valley region of southwest British Columbia, due largely to isostatic depression. At the same time, sea level was 150 m lower than present in Haida Gwaii, on the northern coast of British Columbia, due to the combined effects of the forebulge raising the land and lower eustatic sea level. A forebulge also developed in parts of southeast Alaska resulting in post-glacial sea levels at least 122 m lower than present and possibly as low as 165 m. On the coasts of Washington and Oregon, as well as south-central Alaska, neotectonics and eustasy seem to have played larger roles than isostatic adjustments in controlling relative sea-level changes. [ABSTRACT FROM AUTHOR]

Morphostratigraphic relationships between landforms and sediments, comparative boulder weathering status, and paired 10Be and 26Al exposure ages indicate the occurrence of at least three separate glaciations that are interpreted as dating from MIS 2, 6 and possibly 8. The Rhona Glacier remained at or close to its greatest LGM extent until ~17.6 ka due to a very favourable micro-climate that resulted from local topography. That these factors were sufficient to over-power relatively subtle zonal temperature shifts that caused significant changes in more exposed Tasmanian glaciers implies a need for caution in correlating between glacier systems in markedly different topographic settings when environmental conditions are only marginally supportive of glaciation. No evidence was detected for any greater ice extent during MIS 3 or MIS 4 than during MIS 2, but much more extensive glaciations occurred during earlier glacial climatic cycles. Reduced local precipitation in parallel with increasing aridity of the Australian continent may account for the progressively diminishing maximum extent of glaciers during the latter part of the Pleistocene, and it would have emphasized the importance of local topography and microclimate for the glaciers of southwest Tasmania. [ABSTRACT FROM AUTHOR]

We present a new glacier chronology from one of the major end moraine systems of the Southern Alps. Timing and extent of the Last Glacial Maximum (LGM) advance of the Ticino-Toce glacier were reconstructed in detail based on landform relationships and surface exposure dating. 10Be and 36Cl ages from 41 erratic boulders constrain the last maximum of the Ticino-Toce glacier to have lasted from 25.0 ± 0.9 ka to 19.9 ± 0.7 ka. Over this period of ca. 5000 years the Ticino-Toce glacier underwent only minor oscillations, during which the glacier front remained close to its LGM maximum position. Underpinned by our detailed geomorphological reconstruction, the ages further demonstrate that the Verbano piedmont lobe was significantly larger (about 200 km2) than shown on recent maps. A short-lived glacier readvance around 19.7 ± 1.1 ka terminated internal to the LGM maximum margins. Collapse of the Verbano lobe must have set in soon after and final withdrawal from the foreland occurred no later than 19 ka. The new Ticino-Toce chronology matches temporal constraints of major glacier systems emerging from adjacent Alpine accumulation areas. This points to in-phase glacier advances across the Western Alps, apart from the southwestern massifs for which a slightly earlier reaching of the Late Pleistocene maximum position of the Lyon lobe was shown recently. A two- potentially three-fold LGM advance structure with intervening retreat intervals, as reported for two major amphitheatres (Garda, Tagliamento) to the east is distinctly not supported by our data for the Ticino-Toce glacier. This contrast in glacier behaviour between the central and eastern Southern Alps is ascribed to shifting precipitation patterns after ca. 23–22 ka, away from southern to predominantly northwestern air flow and a greater independence of southerly moisture transport for the central Southern Alps. • Last Glacial Maximum of Ticino-Toce glacier was ∼200 km2 larger than thought. • From ∼25 to 19.9 ka Ticino-Toce glacier oscillated close to its maximum position. • A glacier readvance around 19.7 ± 1.1 ka was short-lived. • Ticino-Toce glacier was in phase with other glacier systems of the Western Alps. • Central southern Alpine glaciers may have been less dependent on southerly moisture. [ABSTRACT FROM AUTHOR]

An understanding of Antarctic Ice Sheet (AIS) behavior is important for future sea-level predictions. Here, we examine past ice-sheet history in the McMurdo Sound region of the western Ross Sea over the last two glacial-interglacial cycles in order to gain insight into the drivers of ice-sheet change. Surficial mapping, along with radiocarbon dates of lacustrine algae and uranium-thorium disequilibrium dates of lacustrine carbonates from ice-dammed lakes, allow reconstruction of the timing and origin of grounded ice in McMurdo Sound during the last glacial maximum (LGM) and penultimate glaciation. During the LGM, ice-surface elevation profiles and distribution of erratics indicate ice flow into southern McMurdo Sound from the Ross Sea, rather than seaward expansion of local glaciers from the Royal Society Range. The grounded ice in McMurdo Sound flowed westward to block the mouths of valleys in the Royal Society Range and to dam proglacial lakes. In Marshall Valley, maximum ice extent during what is termed the Ross Sea glaciation, was achieved by 18 ka and remained close to this position until after 14 ka. The pattern of surficial deposits suggests that ice during the penultimate glaciation, locally named the Marshall glaciation, was slightly more extensive than that of the LGM but had a similar Ross Sea origin. Maximum ice extent in Marshall Valley occurred at ∼145–150 ka; the grounded ice may have receded from the valley mouth shortly after 138 ka. Both ice expansions occurred broadly during times of low Antarctic air temperatures, which have been linked to insolation minima. However, the lack of widespread surface melting ablation zones on the AIS indicates that the link between ice expansion and orbital forcing is likely to be indirect and possibly driven through the ocean. Closer examination of the precise timing of the glacial maxima in Marshall Valley shows that the Marshall glaciation occurred synchronously with the penultimate global maximum; ice recession took place during Termination II. In contrast, maximum ice extent during the Ross Sea glaciation along the Royal Society Range occurred after the global LGM, during Termination I. Deglaciation was primarily an early Holocene event. We attribute this delayed maximum and deglaciation (relative to global events) to the effect of rising accumulation on ice-sheet mass balance. • 4214C and 25 234U/230Th dates constrain Ross Sea ice during the last two glacial cycles. • The last glacial maximum in McMurdo Sound occurred at 14–18 ka. • The penultimate glacial maximum in McMurdo Sound occurred at 145–150 ka. • Ice in McMurdo Sound during these glaciations was from the Ross Sea, not local glaciers. • Grounding of ice in the Ross Sea likely was due to a marine mechanism. [ABSTRACT FROM AUTHOR]

Mountain glacier records offer important constraints on the timing and magnitude of climate variability during the last glacial cycle. Existing moraine chronologies from the central Southern Alps indicate maximum ice extent was achieved during marine isotope stages 3–4, followed by repeated advances of similar, but gradually declining extent during marine isotope stage 2, until onset of the glacial termination. Questions remain over the precise role of climate in driving these changes, as most existing moraine chronologies come from large, complex former valley glacier systems, where non-climatic influences such as changing bed topography and proglacial lake formation may have influenced glacier length changes. Here we address this problem via a new cosmogenic 10Be chronology and equilibrium line altitude reconstruction from a cirque glacier situated in Fiordland, New Zealand. Our chronology shows moraine deposition at 32 ± 11 ka, 18.7 ± 0.2 ka, 18.1 ± 0.1 ka, and c. 17.2 ± 0.3 ka. The simple geometry of the former glacier supports the role of climate in driving a net decline of regional ice volume during marine isotope stages 3–2. Close spacing and good preservation of the 19–17 ka moraines permits 2D glacier reconstruction which suggests the equilibrium line altitude remained depressed by c.1130 m (equivalent to 5.8 ± 0.6 °C colder than present) during this interval. Onset of warming after 17.2 ± 0.2 ka is consistent with climate proxy evidence for a sustained southward shift in the southern westerly winds, which may have promoted deglaciation via shifting ocean currents and promoting increases in atmospheric carbon dioxide. • Moraine ages from southern New Zealand constrain ice extent during last glacial. • Equilibrium line altitude was 1100 m lower than present at the Last Glacial Maximum. • Regional air temperatures remained depressed by c. 6 °C until 17 ka. [ABSTRACT FROM AUTHOR]