Glacier Fluctuations Research Articles

10Be chronology of the Last Glacial Maximum and Termination in the Andes of central Chile: The record of the Universidad Glacier (34° S)

Reconstructing mid-latitude glacier variations is a prerequisite for unveiling the interhemispheric climate linkages and atmospheric-ocean forcings that triggered those changes during the last glacial cycle. Nonetheless, the timing, magnitude, and structure of glacier fluctuations in the southern mid-latitudes remain incomplete. Here, we present a new 10Be chronology of the Universidad Glacier in the Andes of central Chile (34° S, 70° W; ∼2500 m a.s.l.) based on 21 cosmogenic-exposure ages of boulders on discrete moraine ridges defining former ice margins. Our findings include the mapping and dating of three moraines, UNI I, UNI II, and UNI III, located ∼20 km, 15 km, and 10 km down-valley from the present-day glacier front, respectively. The 10Be exposure ages of the UNI I moraine range from 135.9 ± 7.1 to 51.4 ± 2.7 ka (n = 3). The UNI II moraine gave a mean age of 18.0 ± 0.9 (n = 15) and the UNI III moraine yielded a mean age of 13.9 ± 0.8 ka (n = 3). The UNI I moraine implies the largest ice extent during a pre-Last Glacial Maximum (pre-LGM) period, including the penultimate glaciation. The UNI II is a moraine complex that represents cold and humid conditions in central Chile at the end of the LGM, which we attribute to the northward-shift of the Southern Westerly Winds (SWW). The UNI III moraine represents a return to glacial conditions interrupting the Termination, evidencing both a double-step deglacial trend observed through the southern middle and high latitudes at the end of the last ice age. The Andes at this subtropical latitude record a global signal of glacial and climate change.

New evidence of glacier advances during Lateglacial Interstadial deciphered from facies evolution in proglacial lacustrine basins of the Maurienne Valley, French Alps

Sedimentological analysis of glaciolacustrine deposit in the French Alps provides an opportunity to elucidate poorly understood glacier fluctuations during the Lateglacial Interstadial. This study focuses on two proglacial lacustrine basins in the Maurienne Valley, Le Verney and Lanslebourg, recording sediment deposition during the Lateglacial. Sedimentological and soft sediment deformation analyses were conducted on these glaciolacustrine sedimentary deposits to constrain the dynamic of the Arc glacier. At Le Verney, the sedimentary succession records the deposition of a proglacial subaquatic fan under supercritical conditions, transitioning to a Gilbert delta-type sedimentation, indicating glacier retreat. Fluid overpressure, shear deformations, and compressional stresses found within Gilbert delta-type sediment marks a subsequent glacier advance. In the Lanslebourg basin, sedimentary deposits display supercritical and subcritical conditions, separated by deposition under a hydraulic jump characteristic of ice contact delta. In this area, glacier advance is recorded by a more proximal condition toward the top of the sedimentary succession, along with a transition to a subglacial condition. These findings reveal glacier advances during the Bølling-Allerød Interstadial, providing the first evidence of glacier re-advances in the French northern Alps during this warming period. This result highlights the complex interactions between local climate, glacier dynamics, and topography.

The LGM termination in the southeastern Tibetan plateau: View from high-frequency LGM glacier fluctuations in the Boshula mountain range

Climate processes that operated during the end of the Last Glacial Maximum (LGM) are remarkable for its global synchroneity. Atmospheric CO2 concentrations have been widely seen as its cause. However, the stepwise LGM deglaciation of mountain glaciers in both hemispheres complicates this view, and signifies additional factors that likely prompted the onset of LGM termination. Here, we examine LGM climate change in the Hengduan Mountains (HDM), southeastern Tibetan Plateau (TP), based on 10Be surface exposure dating of moraine boulders (n = 51). The timing of four moraine-building events is constrained to 22.8 ± 1.0 ka, 21.2 ± 0.6 ka, 20.4 ± 0.6 ka, and 19.2 ± 0.6 ka. These precisely-dated events provide convincing evidence of millennial-to centennial-scale glacial activities in the TP during the LGM. We show that these high-frequency glacier fluctuations likely reacted to a combination of changes in regional summer temperature related to sea surface temperatures as well as monsoon precipitation. The pronounced glacial retreat is dated at 19.2 ± 0.6 ka, representing the end of the LGM in the HDM. That is, the onset of LGM termination preceded the rapid CO2 rise at ∼18 ka. We suggest that the LGM termination in the southeastern TP was initiated by ice-sheet shrinkage, which induced changes in summer temperature and monsoon precipitation via ocean-atmosphere interactions.

Research on Glacier Changes and Their Influencing Factors in the Yigong Zangbo River Basin of the Tibetan Plateau, China, Based on ICESat-2 Data

The intense changes in glaciers in the southeastern Tibetan Plateau (SETP) have essential impacts on regional water resource management. In order to study the seasonal fluctuations of glaciers in this region and their relationship with climate change, we focus on the Yigong Zangbo River Basin in the SETP, extract the annual and seasonal variations of glaciers in the basin during 2018–2023, and analyze their spatio-temporal characteristics through the seasonal-trend decomposition using the LOESS (STL) method. Finally, combining the Extreme Gradient Boosting (XGBoost) model and the Shapley additive explanations (SHAP) model, we assess the comprehensive impact of meteorological factors such as temperature and snowfall on glacier changes. The results indicate that glaciers in the Yigong Zangbo River Basin experienced remarkable mass loss during 2018–2023, with an average annual melting rate of −0.83 ± 0.12 m w.e.∙yr−1. The glacier mass exhibits marked seasonal fluctuations, with increases in January–March (JFM) and April–June (AMJ) and noticeable melting in July–September (JAS) and October–December (OND). The changes over these four periods are 2.12 ± 0.04 m w.e., 0.93 ± 0.15 m w.e., −1.58 ± 0.19 m w.e., and −1.32 ± 0.17 m w.e., respectively. Temperature has been identified as the primary meteorological driver of glacier changes in the study area, surpassing the impact of snowfall. This study uses advanced altimetry data and meteorological data to monitor and analyze glacier changes, which provides valuable data for cryosphere research and also validates a set of replicable research methods, which provides support for future research in related fields.

Outburst flood events since the Last Glacial Maximum in the Hutiao Gorge of Jinsha River: Geomorphological evidence from eddy gravel bars

Breaching of natural dams in the Hutiao Gorge of the Jinsha River across the Yulong-Haba Mountains is one of the major geomorphological events in the largest river of Asia. Catastrophic flood events have an important influence on the geomorphological evolution of the First Bend of the Yangtze River since the Last Glacial Maximum (LGM). However, detailed geomorphological evidence, ages, and depositional phases of outburst flooding remain unclear. In this paper, large-scale gravel bars overlying the river terraces and dammed lakes are analyzed within the Daju Basin. The macroscopic geomorphological characteristics of megaflood landforms with large thickness and uniform gravel bars are similar to those of Missoula and Altai megafloods. Morphological analysis shows that eddy gravel bars (EGBs) with rhythmic structure are characterized by a dome-shaped protrusion in the cross section and a gravel mound in the longitudinal section. Each bar with oblique, parallel and massive bedding was analyzed from the horizontal and vertical directions. Three dome-shaped bars clearly show at least three palaeoflood phases. Quartz grain surface macrotextures are mainly V-shaped pits and conchoidal fractures, which exhibits a high-energy environment during the flood. The stratigraphic sequence model of EGBs is dominated by coarse sand and fine gravel rhythmic bedding in high-energy eddy environments and suspended sand deposits in low-energy backwater environments. Such phenomenon reveals megaflood fluctuates, which is also confirmed by geochemical difference. The episode of natural dam break floods triggered by tectonic activity and glacier fluctuation was dated to 20–17 ka during the LGM. Sedimentary pattern of EGBs offers fresh insights into understanding the megaflood geomorphological characteristics of the upper Yangtze River and better identification similar high-energy palaeoflood landforms in the southeast Tibetan Plateau.

Late Quaternary glacial maxima in southern Patagonia: insights from the Lago Argentino glacier lobe

Abstract. Determining the timing and extent of Quaternary glaciations around the globe is critical to understanding the drivers behind climate change and glacier fluctuations. Evidence from the southern mid-latitudes indicates that local glacial maxima preceded the global Last Glacial Maximum (LGM), implying that feedbacks in the climate system or ice dynamics played a role beyond the underlying orbital forcings. To shed light on these processes, we investigated the glacial landforms shaped and deposited by the Lago Argentino glacier (50° S), an outlet lobe of the former Patagonian Ice Sheet, in southern Argentina. We mapped geomorphological features on the landscape and dated moraine boulders and outwash sediments using 10Be cosmogenic nuclides and feldspar infrared stimulated luminescence (IRSL) to constrain the chronology of glacial advance and retreat. We report that the Lago Argentino glacier lobe reached more extensive limits prior to the global LGM, advancing during the middle to late Pleistocene between 243–132 ka and during Marine Isotope Stage 3 (MIS 3), culminating at 44.5 ± 8.0 and at 36.6 ± 1.0 ka. Our results indicate that the most extensive advance of the last glacial cycle occurred during MIS 3, and we hypothesize that this was a result of longer and colder winters, as well as increased precipitation delivered by a latitudinal migration of the Southern Westerly Winds belt, highlighting the role of local and regional climate feedbacks in modulating ice mass changes in the southern mid-latitudes.

Late Glacial-Holocene cirque glacier chronology on sub-Antarctic Kerguelen Archipelago (49°S) based on cosmogenic 36Cl exposure dating

Sub-Antarctic glacier chronologies can provide valuable information about the past variability of climate dynamics in the Southern Ocean region. The Kerguelen Archipelago (49°S) is advantageously located under the influence of the Southern Hemisphere's westerly wind belt, thus fluctuations of climate-sensitive glaciers on Kerguelen can provide a baseline for understanding the behavior of this atmospheric regime in response to climatic forcings. We present 17 36Cl exposure ages of moraine and erratic boulders to provide chronological constraints to paleoglacier extents of the Guynemer cirque glacier, located just north of the Cook Ice Cap. Erratic boulders show ice thinning in the Guynemer region started to occur in the Late Glacial by 13.5 ka and continued past 12.4 ka. Ice retreat was punctuated by the formation of two moraine stages, the outermost at 11.5 ± 0.4 ka followed by another at 10.4 ± 1.2 ka, which are indicative of Early Holocene glacier advances/standstills. A glacial advance occurred at 1.4 ± 0.3 ka, which corroborates other Late Holocene re-advances elsewhere on the archipelago. Finally, three undated moraine stages are found between 1.4 ka and the 1960s. The lack of moraines after 10.4 ka and through the Mid-Holocene suggests that the Guynemer glacier was significantly smaller during this extended period of the Holocene compared to its Early Holocene as well as its Late Holocene limits. The Guynemer glacier history provides unique evidence of Early Holocene moraines on Kerguelen, which have not been discovered thus far on the archipelago. Similar to glaciers in Patagonia, New Zealand and South Georgia, the Guynemer glacier was at its largest Holocene extent in the Early Holocene. However, while other southern mid-latitude glacier chronologies show progressively smaller glacial extents throughout the Mid- to Late Holocene, the Late Holocene re-advance of the Guynemer glacier, like other Kerguelen glaciers, likely exceeded its Mid-Holocene extent.

Regional beryllium-10 production rate for the mid-elevation mountainous regions in central Europe, deduced from a multi-method study of moraines and lake sediments in the Black Forest

Abstract. Beryllium-10 cosmic-ray exposure (CRE) dating has revolutionized our understanding of glacier fluctuations around the globe. A key prerequisite for the successful application of this dating method is the determination of regional production rates of in situ accumulated 10Be, usually inferred at independently dated calibration sites. Until now, no calibration site has been available for the mid-elevation mountain ranges of central Europe. We fill this gap by determining in situ 10Be concentrations in large boulders on moraines and by applying radiocarbon and infrared-stimulated luminescence (IRSL) dating to stratigraphically younger lake sediments in the southern Black Forest, SW Germany. The dating methods yielded concordant results, and, based on age–depth modelling with 14C ages, the age of a cryptotephra, and IRSL ages, we deduced a regional 10Be production rate in quartz. Calibrating the Black Forest production rate (BFPR) in the Cosmic-Ray Exposure program (CREp) resulted in a spallogenic sea-level and high-latitude (SLHL) production rate of 3.64±0.11 atoms 10Be g−1 quartz a−1 when referring to time-dependent Lal–Stone scaling, the European Reanalysis (ERA)-40 atmosphere model, and the atmospheric 10Be-based geomagnetic database in CREp. The BFPR turned out to be ∼11 % lower than both those at the nearest calibration site in the Alps (4.10±0.10 atoms 10Be g−1 quartz a−1 at SLHL) and the canonical global 10Be production rate (4.11±0.19 atoms 10Be g−1 quartz a−1 at SLHL) in CREp. A stronger weathering and snow cover bias and a higher impact of forest, soil, moss, and shrub cover at the study site likely explain this discrepancy.

Influence of the last (de)glaciation on a complex cave system: Grønli-Seter cave system, Northern Norway

Cave studies enable us to unravel valuable information on landscape evolution. In glacial settings, the glacial cycles induced fluctuations in the underground hydraulic regime, sediment availability and base level in adjacent caves. Here, we present our work on the Grønli-Seter cave system in Northern Norway, which comprises >8 km of passage length at an elevation between 250 m and present sea level. By linking cave morphology and deposits to shifting glacier configurations and external base level changes during the last deglaciation and the Early Holocene, we establish how the hydraulic conditions in the cave system shifted in pace with glacier fluctuations. Maze sections and phreatic loops appear in a hydraulic confined setting close to the interface between the calcite marble and the overlying mica schist. Scallops in the cave walls demonstrate slow, ascending water flow, evidence of subglacial speleogenesis under wet-based, topographically constrained glaciers with a gentle surface slope. Moreover, cave morphology and clastic deposits indicate various hydrological phases of descending water flow, stagnant conditions, and excessive flow rates. Our work establishes that the last glaciation and deglaciation had an insignificant effect on the cave system's solutional development. In contrast, the cave sediments reveal diverse hydraulic conditions that may be related to shifting glacier configurations. This research offers valuable insights into glacier ice-contact speleogenesis and landscape development in glacial terrains.

Anti-phase glacier fluctuations on the millennial-scale on the southern Tibetan Plateau and New Zealand during the last glacial period

The sparsity of high-resolution 10Be chronologies in the Northern Hemisphere makes it difficult to determine whether the global fluctuations in glacier extent during the last glacial occurred simultaneously. This limits our understanding of the past mechanisms driving global climate changes. We compiled and reanalyzed 476 10Be exposure ages from the southern Tibetan Plateau for the last glacial and compared them with coeval 10Be ages from the Southern Alps. The results indicate an anti-phase relationship between the glacier expansions in these two regions on the millennial-scale during the last glacial period. Comparison with a glacier-derived temperature reconstruction suggests that maintaining a stable glacier state in both regions required a similar cooling magnitude. We speculate that variability of the Atlantic Meridional Overturning Circulation, which induced poleward/equatorward shifts in atmospheric and oceanic circulation, was the primary driving mechanism of this anti-phase relationship. Our findings provide glacial geological evidence to support the bipolar seesaw hypothesis.

Late-glacial fluctuations of Himalayan glaciers: 10Be surface exposure dating northwest of Mt. Gang Benchhen

Robustly-dated glacial landforms provide us a means of examining millennial-scale climate events during the late-glacial period, which could shed new light on the bipolar seesaw hypothesis. Although many moraines are proposed to be late-glacial in age across the Himalayas, the well-determined late-glacial moraine sequences remain extremely rare in the central Himalaya (e.g. the Paiku Gangri area). The paucity of high-precision chronologies limits our ability to fully explore the response of Himalayan glaciers to late-glacial climate reversals. Here, we present a detailed geomorphic map of glaciers in the Laqu River Valley, northwest of Mt. Gang Benchhen and a10Be-based moraine chronology from 24 boulders from the late-glacial period. The dating results indicate that glaciers in the studied catchment reached their maximum late-glacial extent about 16.1 ka ago, prior to the Younger Dryas Stadial (YDS), and that a following glacial culmination occurred at 12.2 ± 0.9 ka, corresponding roughly to the YDS. The emerging pattern of glacial fluctuations is similar at local, regional, and global scales, suggesting a interhemispheric coherency of late-glacial glacier behaviors. The Analysis of dynamic response of Himalayan glaciers to climate change suggests a temperature-sensitive mountain-glacier system, supporting the view that the bipolar seesaw was primarily a northern winter phenomenon during the late-glacial interval.

Fluctuaciones recientes del glaciar Alerce (1953-2020), Andes de Patagonia norte

In recent decades, glacier retreat has been observed in all the world’s mountain ranges. Over the last 20 years, glaciers in the Andes have lost mass at one of the highest rates on record. Particularly, glaciers in the northern Patagonian Andes show the highest rate of loss of all the Andean regions for the last decade. Detailed records of long-term variations in glacier extent are crucial to put current climate change into context and quantify its impact on mountain areas. In the present study, a reconstruction of the extension (length and area) of the Alerce glacier (41.15° S-71.81° W) for the last 70 years was carried out. By means of historical documents and satellite images (Landsat and Pléiades), detailed maps of glacier fluctuations were generated for the period 1953-2020. Four methodologies were evaluated to measure the front position: i) central flow line; ii) curvilinear box; iii) multiline; and iv) variable box. The magnitude of the front position variations depends on the methodology applied. The method that best addresses glacier front variations over the period analyzed is the variable box method. Between 1953 and 2020, the Alerce glacier lost 35% of its area (1.1±0.1 km2) and 67% of its total length (1.49±0.04 km). It is possible to distinguish periods with different rates of retreat. A stage of slight retreat (-11.3±0.5 ma-1) between 1953 and 1976, followed by a period of stability (-6.7±0.5 ma-1) between 1977 and 1983, then a strong retreat (-58.7±0.5 ma-1) between 1984 and 1999, followed by another period of stability (-5.4±0.5 ma-1) between 2000 and 2009 and, finally, another retreat (-8.7±0.5 ma-1) between 2010 and 2020. The retreat rates for the Alerce glacier mimic those observed in other glaciers in the region, possibly representing a regional climatic signal.

Glacier fluctuation chronology since the latest Pleistocene at Mount Rainier, Washington, USA

Abstract Large stratovolcanoes in the Cascade Range have high equilibrium-line altitudes that support glaciers whose Holocene and latest Pleistocene advances are amenable to dating. Glacier advances produced datable stratigraphic sequences in lateral moraines, which complement dating of end moraines. New mapping of glacial deposits on Mount Rainier using LIDAR and field observations supports a single latest Pleistocene or early Holocene advance. Rainier R tephra overlies deposits from this advance and could be as old as >11.6 ka; the advance could be of Younger Dryas age. Radiocarbon ages on wood interbedded between tills in the lateral moraines of Nisqually, Carbon, and Emmons glaciers and the South Tahoma glacier forefield suggest glacier advances between 200 and 550 CE, correlative with the First Millennium Advance in western Canada, and during the Little Ice Age (LIA) beginning as early as 1300 CE. These results resolve previous contradictory interpretations of Mount Rainier's glacial history and indicate that the original proposal of a single pre-Neoglacial cirque advance is correct, in contrast to a later interpretation of two advances of pre- and post-Younger Dryas age, respectively. Meanwhile, the occurrence of the pre-LIA Burroughs Mountain Advance, interpreted in previous work as occurring 3–2.5 ka, is questionable based on inherently ambiguous interpretations of tephra distribution.

Fluctuations of Qiangyong glacier in southern Tibetan Plateau over the past 500 years recorded by proglacial lacustrine sediments

The glaciers of the Tibetan Plateau have undergone profound changes due to rapid global warming, but the nature of their response to climate change at various settings remains unclear. This study focuses on the analysis (grain sizes, magnetic susceptibility, and element ratios) of a sedimentary core from a proglacial lake (Qiangyong (QY) Co) at the southern Tibetan Plateau, based upon the 210Pb and 137Cs dating, aiming to unveil the fluctuations of the QY glacier over the recent 500 years and its response to global warming. Four pre-1900s distinct glacier advance/cold intervals (C1: 1560s, C2: 1660s, C3: 1760s and C4: 1860s), a minor advance in the 1950s and an extensive glacier retreat since the 2010s were discerned. There are five glacier fluctuation cycles, each spanning approximately 100 years, correlating generally well with the Northern Hemisphere temperature patterns on a century time scale. The glacier advances align with the cold periods, whereas the retreats correspond to the warm intervals. However, coarse grain sizes indicated a marked glacier shrinkage of the QY glacier since the 1920s owing to global warming, over-shading the inherent 100-years fluctuation cyclic variations intrinsic to glaciers. The reason is that after QY glacier has significantly shrunk to higher altitude, the response of the glacier to climate change is no longer as sensitive as at the lower altitude, even under post-industrial-revolution warming. The QY glacier and even the entire Himalayan region will face the threat of glacier melting during the 21st century, but dynamic patterns of glacier retreats in higher Himalayan regions may differ from that in the low-altitude.

10Be surface exposure dating of glacier fluctuations on the eastern slope of Mount Geladandong, central Tibetan Plateau

Moraine complexes formed by multiple glaciations are well-preserved in the Mount Geladandong area, the largest center of current glaciation in the Tanggula Mountains in western China. Studies of these glacial landforms provide insights into past glacier changes and contribute to understanding palaeoclimate and palaeoenvironment in the central Tibetan Plateau (TP). Here we report on 10Be surface exposure dating of thirteen rock samples collected from a sequence of glacial landforms associated with the Gangjiaquba Glacier. Based on the dating results, historical records (topographical maps) and morphological relationships, clear Little Ice Age (LIA) landforms are identified, and other landforms are tentatively assigned Neoglacial and global Last Glacial Maximum (LGMG) ages. Dating results for samples from modern glacial landforms demonstrate that the boulders were not affected by nuclide inheritance, and that 10Be surface exposure dating may be used to constrain glacier fluctuations during the past century in high-altitude areas that have high 10Be production rates. A comparison of the ages of a glacially polished surface and adjacent glacial deposits indicates that subglacial erosion by abrasion of the rock surface was insufficient to remove cosmogenic nuclide inventories. Thus the apparent exposure age on the polished surface includes inheritance and over-estimates the actual age for the exposure of this surface. Samples from hummocky moraine have wide age spreads, indicating long-lasting surface instability after deposition of this landform. Successive reduction in glacial extent in the Mount Geladandong area since the LGMG reflects temperature and precipitation changes over this timeframe in the central TP, with climate forcing for glacial advances correlated with cooling signals in the North Atlantic that may have been transmitted to this area by the westerlies.

Late Holocene glacier and climate fluctuations in the Mackenzie and Selwyn mountain ranges, northwestern Canada

Abstract. Over the last century, northwestern Canada experienced some of the highest rates of tropospheric warming globally, which caused glaciers in the region to rapidly retreat. Our study seeks to extend the record of glacier fluctuations and assess climate drivers prior to the instrumental record in the Mackenzie and Selwyn mountains of northwestern Canada. We collected 27 10Be surface exposure ages across nine cirque and valley glacier moraines to constrain the timing of their emplacement. Cirque and valley glaciers in this region reached their greatest Holocene extents in the latter half of the Little Ice Age (1600–1850 CE). Four erratic boulders, 10–250 m distal from late Holocene moraines, yielded 10Be exposure ages of 10.9–11.6 ka, demonstrating that by ca. 11 ka, alpine glaciers were no more extensive than during the last several hundred years. Estimated temperature change obtained through reconstruction of equilibrium line altitudes shows that since ca. 1850 CE, mean annual temperatures have risen 0.2–2.3 ∘C. We use our glacier chronology and the Open Global Glacier Model (OGGM) to estimate that from 1000 CE, glaciers in this region reached a maximum total volume of 34–38 km3 between 1765 and 1855 CE and had lost nearly half their ice volume by 2019 CE. OGGM was unable to produce modeled glacier lengths that match the timing or magnitude of the maximum glacier extent indicated by the 10Be chronology. However, when applied to the entire Mackenzie and Selwyn mountain region, past millennium OGGM simulations using the Max Planck Institute Earth System Model (MPI-ESM) and the Community Climate System Model 4 (CCSM4) yield late Holocene glacier volume change temporally consistent with our moraine and remote sensing record, while the Meteorological Research Institute Earth System Model 2 (MRI-ESM2) and the Model for Interdisciplinary Research on Climate (MIROC) fail to produce modeled glacier change consistent with our glacier chronology. Finally, OGGM forced by future climate projections under varying greenhouse gas emission scenarios predicts 85 % to over 97 % glacier volume loss by the end of the 21st century. The loss of glaciers from this region will have profound impacts on local ecosystems and communities that rely on meltwater from glacierized catchments.

Coupled climate-glacier modelling of the last glaciation in the Alps

Abstract Our limited knowledge of the climate prevailing over Europe during former glaciations is the main obstacle to reconstruct the past evolution of the ice coverage over the Alps by numerical modelling. To address this challenge, we perform a two-step modelling approach: First, a regional climate model is used to downscale the time slice simulations of a global earth system model in high resolution, leading to climate snapshots during the Last Glacial Maximum (LGM) and the Marine Isotope Stage 4 (MIS4). Second, we combine these snapshots and a climate signal proxy to build a transient climate over the last glacial period and force the Parallel Ice Sheet Model to simulate the dynamical evolution of glaciers in the Alps. The results show that the extent of modelled glaciers during the LGM agrees with several independent key geological imprints, including moraine-based maximal reconstructed glacial extents, known ice transfluences and trajectories of erratic boulders of known origin and deposition. Our results highlight the benefit of multiphysical coupled climate and glacier transient modelling over simpler approaches to help reconstruct paleo glacier fluctuations in agreement with traces they have left on the landscape.

Moisture amplification of the high-altitude deglacial warming

In response to anthropogenic warming, glaciers are shrinking almost everywhere, endangering water accessibility in areas located downstream. Glacier fluctuations are at first order controlled by local precipitation and temperature, but large uncertainties persist on the potential role of local moisture in amplifying or dampening temperature changes at high-elevation. Here, we combine glacier extents and Sea Surface Temperature (SST) during the Last Glacial Maximum (LGM) to quantify altitudinal thermal gradients (lapse rate) from 40°N to 40°S along the American Cordillera. We also constrain modern lapse rates based on present day temperature and SST database to explore how the lapse rate has changed since the LGM along this North South transect. Based on proxy-based quantitative paleo-precipitation estimations above 2000 m, we investigate how these lapse rate changes compare with moisture modifications around the Cordillera and discuss the mechanisms that potentially controlled lapse rate changes during the post-LGM deglacial warming.We find that lapse rate changes are linearly related to changes in precipitation and derive a quantitative relationship between these two parameters. To further explore the processes involved in controlling lapse rate variations, we use the IPSL global climate model outputs, for the LGM and pre-industrial states in this region. The IPSL model also yields a shallower modern lapse rate in the wetter tropical region, confirming the observed correlation between precipitation changes and lapse rate variations. The IPSL model also supports a close coupling of continental relative moisture and mean annual precipitation in the studied area, indicating that moisture is involved in the precipitation – lapse rate relationship. Our results suggest that future warming may be enhanced in high altitude regions where precipitation is expected to increase. Using our most reliable relationship linking precipitation and lapse rate changes, we conclude that, assuming a 1 °C warming at sea level, a mean annual precipitation increases of 500 mm.a−1 could lead to a warming amplification of 4.1 ± 0.8 °C at 4000 m asl (mean elevation of modern glaciers). In this case, a 2 °C warming at sea level would yield >6 °C degrees warming at 4000 m asl. This study therefore confirms that special attention should be given to the climate projections of glacier melting in tropical and mid latitude regions.

Triggers for multiple glacier detachments from a low-angle valley glacier in the Amney Machen Range, eastern Tibetan Plateau

Large-scale ice avalanches initiated from low-angle glaciers (also known as glacier detachment) remain a scarcely studied and poorly understood phenomenon. Here we re-evaluated the repeat glacier detachments of a low angle (~14°) surging valley glacier in the Amney Machen Range, eastern Tibetan Plateau. Four glacier detachments recorded over a 15-year period (2004–2019) are described in detail based on the combination of satellite image analyses, additional terrain profile analyses and field data. To identify what triggered these high magnitude events, the glacier fluctuations, seismicity, lithology, and regional climate were examined. We find that the factors favouring glacier detachments were anomalous warming, subglacial hydrology, repeated glacier surging, a soft glacier bed, and ice-rock loading from the glacier headwall, though the relative influence of each factor varied in the four events we studied. We confirmed the observation of Paul (2019) that additional ice-rock debris loadings from the headwall were the most important factor for all events. The 2004 event probably was a delayed response to ice-rock loading during the preceding months. The latter three events may have been affected by short-term climate anomalies. The events of 2007 and 2016 were associated with anomalously high temperature: abrupt warming preceded the 2007 event and 2016 was the warmest year on record. The 2019 event followed sustained precipitation and high summer temperatures. Based on the spatial patterns in glacier change, we suggest that climate warming played a limited role in initiation.

Glacier fluctuations since the global Last Glacial Maximum in the eastern Tanggula Mountains, China

Distinct moraine complexes are well-preserved at the headwaters of the Requ River valley on the southern slope of Bujia Gangri, the largest center of modern glaciation in the eastern Tanggula Mountains in western China. Dating these moraines is an important step in understanding glacial history, palaeoclimate, and landscape evolution in this region. Surface exposure dating using 10Be was done on twenty-three rock samples from large granitic boulders embedded in moraine crests were collected from the Yongqu River valley and the Daxiong River valley, two glaciated valleys at the headwaters of the Requ River valley. The moraines (MW1 and ME1) closest to the current glaciers in the west (main) and east (hanging) valleys of the Yongqu River valley were dated to 203 ± 51 a (n = 4) and 162 ± 58 a (n = 3); the inner four end moraines (MW3–1) and outer ones (MW3–2) of the third moraine complex (MW3) in the main valley date to 16.8 ± 1.8 ka (n = 3) and 20.7 ± 1.3 ka (n = 2); end moraines (ME2) near the mouth of the east valley and a high lateral moraine (MEL) on its east side date to 18.9 ± 3.0 ka (n = 4); and a high lateral moraine in the Daxiong valley (MDXL) dates to 18.6 ± 1.3 ka (n = 3). The dating results indicate that these moraines were formed during the Little Ice Age (LIA), the Heinrich 1 (H1) event period, and the global Last Glacial Maximum (LGMG). These glacial events are synchronous with those across the Tibetan Plateau (TP) and its surrounding mountains. Combining the palaeoclimatic and palaeoenvironmental proxies in the TP and its surroundings, we infer that the cooling during the LIA, H1, and LGMG was a main control for these glacial advances.