Glacier Advances Research Articles

Late pleistocene glacial history of Mount Karadağ, SW Türkiye

Glacial landforms in the southwestern part of the Anatolian Peninsula are found at lower elevations than the rest, suggesting that glaciers were present during the Late Pleistocene. Karadağ, located west of the Western Taurus Mountains, provides evidence of the climatic conditions that facilitated this extensive glaciation. It is characterized by numerous peaks exceeding 2300 m above sea level (asl), with the highest peak reaching 2418 m, making it the region's largest glaciation area. This high mountain mass is composed mainly of limestone and dolomite. This study focuses on the glacial landforms in Karadağ to reconstruct the Late Pleistocene glacial chronology and palaeoclimate of the Western Taurus Mountains. We employed detailed UAV photogrammetry, extensive fieldwork and mapping, surface exposure dating with cosmogenic 36Cl, meteorological measurements, palaeoglacier reconstruction, and palaeo-equilibrium line altitude (pELA) calculations. Karadağ, a topographic barrier to humid air masses from the Mediterranean Sea, ranks as the second wettest area in the Western Taurus Mountains. At a meteorological station we installed in Karadağ, an annual precipitation of 1700 mm or more was recorded, highlighting its significant precipitation. In Karadağ, we have identified two glacial valleys with a maximum length of 4.5 km and six cirques. The glaciers reached their maximum extent around 22.4 ± 2.8 ka during the Last Glacial Maximum (LGM), facilitated by the lowering of the pELA to 2090 m. During the LGM, the glaciers covered an area of approximately 3.5 km2 and reached a maximum thickness of about 140 m. Sample TRKR 10 at 2015 m probably belongs to the LGM period. Although a single sample does not conclude definitive conclusions, the presence of the moraine at its highest position indicates the maximum thickness of the glacier. Following the LGM, two more significant glacier advances occurred during the Lateglacial (15.5 ± 2.7 ka) and the Younger Dryas (12.4 ± 1.1 ka). During the late Pleistocene glaciations, and especially during the LGM, Karadağ probably received more precipitation than today, leading to the formation of glaciers at relatively lower elevations than on the Anatolian Peninsula.

Comparing the evolution of debris-free and debris-covered glaciers during the end of the Lateglacial and the Holocene in Dudh Koshi basin, Everest region, Nepal

Debris-covered glaciers are very frequent geomorphological features in Khumbu Himal (Nepal). Rock debris on the glacier surface play a significant role in glacier-climate relationships and glacier dynamics. These effects may cause an asynchronous evolution of debris-covered glaciers compared to debris-free glaciers at a multicentennial to millennial scale. Here, we explore this hypothesis by documenting and comparing the multi-millennial Holocene evolution of a debris-free glacier, Sabai glacier, and two debris-covered glaciers, Dig and Huuku glaciers, from adjacent catchments in Dudh Koshi basin (Everest region, Nepal). To do so, we dated rock samples collected from moraine boulders on both debris-covered and debris-free glaciers using the 10Be cosmic ray exposure (CRE) dating method. 10Be CRE ages obtained from 41 moraine boulder samples provide time constraints from ∼13.5 ka to 0.1 ka. While at Dig (debris-covered) and Sabai (debris-free) glaciers, no moraines from the Lateglacial and the Early Holocene are preserved, debris-covered Huuku glacier evidenced a large glacier extent during the Bølling-Allerød and Early Holocene with two moraines dated respectively to ∼13.5 ka and 11 ka, synchronously with most debris-free and debris-covered glaciers in this region. These two glacier advances are concomitant with enhanced monsoon precipitation supporting a qualitative relationship. The absence of debris landforms in the main valley question the nature of Huuku glacier during the Bølling-Allerød and Early Holocene, which could have been either debris-free or covered by a thin debris layer only. During the Mid Holocene, significant differences are observed in the evolution of the two glacier types. The two debris-covered glaciers recorded a significant advance at ∼4.8 ka, synchronous with that observed on other debris-covered glaciers in Khumbu valley. However, such glacier advance during the Mid Holocene was not evidenced on debris-free glaciers in the Dudh Koshi valley. Such a Mid Holocene glacier advance may have a spatial signature with frequent cases reported from both types of glaciers in the western part of High Mountain Asia, which are however infrequent in the arid and semi-arid southern and north-eastern Tibet. During the Late Holocene, both types of glaciers evolved similarly again, with moraines spanning the last two millennia, including the Little Ice Age, concomitant with enhanced monsoon precipitation.

Pleistocene glacial advances and exposure age scatter in the Olympus Range, Antarctica: A study of cosmogenic 36Cl/3He in dolerites and 10Be in sandstones

In three cirques in the western Olympus Range of the McMurdo Dry Valleys, Antarctica, previous advances of cirque glaciers are recorded by a sequence of three drifts in each of the cirques. We dated drift limits and the deposits on modern glaciers in two of these cirques, Dean and Dipboye, via cosmogenic 3He in pyroxene from 41 dolerite boulders, 36Cl in pyroxene from 12 of those dolerites, and 10Be in quartz from 11 sandstone boulders. Exposure age scatter is high on all deposits. The 3He exposure ages across all deposits range from ∼35 to ∼2300 ka and 10Be exposure ages range from ∼7 to ∼435 ka. Coupled 36Cl/3He from dolerites support constant exposure with erosion for nine of the 12 samples, while the other three might have experienced complex exposure-burial histories. Due to the mesa-butte topography and slow bedrock erosion rates, nuclide inheritance is the primary cause of age scatter in dolerites, accounting for >1 Myr of exposure age error. Mean exposure ages from sandstones are 2–7 times younger than those from dolerites for the same deposits, indicating that inheritance is less common in sandstones in this region. Weathering analyses of sandstone boulders show an increase in average siliceous crust thickness and rock strength with deposit age, an example of case hardening. Based on both relative and exposure age dating, drift age increases with distance from the modern glaciers in both Dean and Dipboye cirques, with three advances during the past <700 ka. However, due to high exposure age scatter, it cannot be determined if the three drifts are temporally correlated across the two cirques and therefore the drifts might record different glacial advances in Dean Cirque vs. Dipboye Cirque despite the apparent stratigraphic correlation of the drifts. This study has implications for drift depositional processes of cold-based glaciers and the importance of source-bedrock lithology and geomorphology on nuclide inheritance in Antarctica.

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.

Single grain pIRIR dating of glacigenic deposits in the Yuzhu Peak area of Kunlun Mountains of Tibetan Plateau revealed the glaciations during Holocene period

The variations of glaciers in the Kunlun Mountains of the northern Tibetan Plateau are influenced by the complex interaction of the East Asia summer monsoon (EASM), Indian summer monsoon (ISM) and Westerlies, as well as human activity during the Holocene period. Consequently there is ongoing debates regarding the evolution of glaciers and the factors driving their changes. The reconstruction of glacial evolutions in these regions has been hindered by insufficient chronological data for moraines and other glacial landforms. In this study, glacial sediment samples were collected from five moraine sequences located on the southern and northern slopes of the Yuzhu Peak in the Kunlun Mountains. These poorly bleached moraine samples were dated using the single-grain quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating methods. The luminescence characteristics analysis of quartz grains shows that single grain quartz OSL dating cannot be used to date Holocene moraine samples due to the low brightness of quartz OSL signals. Various tests were conducted to assess the reliability of K-feldspar pIR50IR170 dating, including anomalous fading tests, dose recovery, and residual dose tests. The K-feldspar pIR50IR170 ages, determined using the Minimum Age Model (MAM), indicate that during the early Holocene, glaciations have expanded by ∼800 m in length at ∼ 8 ka, and during the end of the Neoglacial period, they extended by ∼200 m in length at ∼ 1 ka. The strengthened ISM precipitation and northward movement of ISM boundary likely contributed to the glacial expansion in the early Holocene. During the end of the Neoglacial period, the increase in westerlies precipitation and cold events may have played a role in the advancement of glaciers.

Late Pleistocene to Holocene vegetation changes in southeastern Patagonia (49° S): landscape changes related to disturbances

ABSTRACTSoutheastern Patagonia's (49° S) post‐glacial history inferred from high Andean lake sediments provides new insights regarding Late Pleistocene and Holocene vegetation dynamics at the eastern margin of the Southern Patagonian Icefield. The fossil records of pollen, charcoal and geochemical data from tephra layers from Laguna Chiquita and Laguna Gemelas Este were analysed to reveal past landscape dynamics related to vegetation changes, fire and volcanic events from ca. 15 200 cal a bp to the present. Nothofagus forest expanded over shrubland communities sometime between 15 200 and 4600 cal a bp, along with at least three disturbance sources related to the volcanic eruptions of Lautaro, Aguilera and Hudson, important local fire episodes, and neoglacial advances. Major charcoal deposition reveals moderate fire activity during the Late Pleistocene related to an open landscape characterised by a grass/shrub steppe. Local glacier advances may have affected the Laguna Gemelas Este sedimentation. Tephra deposition events do not correlate to vegetation changes inferred from the Laguna Gemelas Este and Laguna Chiquita pollen records. Late Holocene eastern Andean forest changes and fire activity at 49° S match other southern palaeoenvironmental records (50–52° S) suggesting that changes in the Southern Westerly Wind latitudinal position and intensity drove major palaeovegetation and fire dynamics before the European settlement. In the last centuries, fire and vegetation changes have been closely related to an increase in local ignition sources and the introduction of alien species.

The post-IR IRSL dating of an ancient dammed lake upstream of the Ganglai gorge in the upper-middle reaches of Yarlung Tsangpo

The middle reaches of Yarlung Tsangpo, situated on the southern Tibetan Plateau, have experienced extensive river damming events due to glacier advances, resulting in the formation of several ancient dammed lakes. These palaeolakes offer invaluable insights into past hydrological and geomorphological dynamics on the Tibetan Plateau. In this study, we reported a newly identified ancient dammed lake, named the Xiaru palaeolake, located upstream of the Ganglai Gorge in the uppermost segment of the middle reaches of Yarlung Tsangpo, and conducted a pioneer chronological investigation of the lake using K-feldspar post-IR IRSL (pIRIR) dating. Quartz minerals from most lacustrine and fluvial sediments can not provide reliable ages characterized with low intensity and large inter-aliquot scatter in equivalent doses (De). In contrast, the K-feldspar exhibited much greater luminescence intensity and narrower De distribution using the pIRIR225 dating protocol. Residual, dose recovery, and fading tests demonstrated that the pIRIR225 signals are well bleached with a relatively low fading rate, making it a more suitable dosimeter for dating applications in the study area. The pIRIR225 ages, derived through single aliquots, standard growth curve (SGC), and single grain measurements, reveal a major phase of the Xiaru Lake between 24.1 ± 1.0 ka and 15.8 ± 1.1 ka, that commenced aligning with the global Last Glacial Maximum. Furthermore, one lacustrine sample dated to 29.9 ± 2.2 ka suggests the possibility of multiple damming events in Ganglai Gorge during the last glacial period, although further evidence is required for a comprehensive interpretation.

The last deglaciation in the central Pyrenees: The 47 ka Pllan d’Están paleolake record (Ésera valley)

Last deglaciation was a complex period in southern European mountains with several glacier advances associated to rapid climate changes which differ in terms of timing and intensity. The 46.7 ka BP lacustrine sequence of Pllan d’Están paleolake (1840 m a.s.l.) located in the Central Southern Pyrenees (northern Spain) provides new information about that deglaciation period for the first time in the Ésera valley. We present a multiproxy analysis including sedimentological, geochemical and biological (pollen and diatoms) indicators that, together with a chronological frame constrained by 14C and OSL dates, enabled the longest reconstruction of the glacier evolution, climate and environmental change made in the Pyrenees to date. This lacustrine sedimentary sequence (4.9 m) is composed of banded to finely laminated silts with few intercalations of massive sections where carbonatic, siliciclastic and organic facies appear from the bottom to the top, characterizing environmental changes from a subglacial/proglacial lake to the current peatbog. A cold and glacier dominated period from 46.7 to 15.9 ka BP was interrupted by a warmer period spanning from 38.2 to 34.8 ka BP. The vegetation succession determined by the palynological analyses is similar to other Pyrenean valleys but dates the onset of mesophytes expansion at 13.8 ka BP during the Allerød, pointing to a difference with other European sequences where temperate forest development took place earlier, associated to the Bølling period. The colder conditions of the Younger Dryas (13–11.7 ka BP) have been detected from cold tolerant diatom taxa that preceded a peatbog development during the Holocene (11.7 ka BP – present-day). These results, together with previously studied Pyrenean sequences, allow characterizing past environmental changes during last deglaciation phases in southern Europe.

A late response of the sea-ice cover to Neoglacial cooling in the western Barents Sea

In high northern latitudes, the Middle to Late-Holocene was a time of orbitally-induced atmospheric cooling. This led to increased sea-ice production in the Arctic Ocean and its export southward, a decrease in sea surface temperatures (SST), and glacier advances at least since 5–4 ka BP. However, the response of the ocean-climate system to decreasing insolation was not uniform. Our research shows that the sea-ice cover in the northwestern Barents Sea experienced a late response to Neoglacial cooling. We analyzed dinoflagellate cyst assemblages from a sediment core from Storfjordrenna, south of Svalbard. We found that the area experienced ice-free conditions throughout most of the Mid- and Late-Holocene. It was only after 2.3 ka BP that the study site became covered with winter drift ice and primary productivity decreased subsequently. Other regional data support the decrease in SST, the expansion of the sea-ice cover, and the deterioration of the environmental conditions around that time. Our findings indicate that the sea-ice cover in the northwestern Barents Sea required a significant amount of time to respond to the general cooling trend in the region. These results have important implications for present-day environmental changes. Even if the current warming trend is revoked in the future, the observed sea-ice loss in the Barents Sea may be incredibly challenging to reverse.

A marine record of Patagonian ice sheet changes over the past 140,000 years

Terrestrial glacial records from the Patagonian Andes and New Zealand Alps document quasi-synchronous Southern Hemisphere-wide glacier advances during the late Quaternary. However, these records are inherently incomplete. Here, we provide a continuous marine record of western-central Patagonian ice sheet (PIS) extent over a complete glacial-interglacial cycle back into the penultimate glacial (~140 ka). Sediment core MR16-09 PC03, located at 46°S and ~150 km offshore Chile, received high terrestrial sediment and meltwater input when the central PIS extended westward. We use biomarkers, foraminiferal oxygen isotopes, and major elemental data to reconstruct terrestrial sediment and freshwater input related to PIS variations. Our sediment record documents three intervals of general PIS marginal fluctuations, during Marine Isotope Stage (MIS) 6 (140 to 135 ka), MIS 4 (~70 to 60 ka), and late MIS 3 to MIS 2 (~40 to 18 ka). These higher terrigenous input intervals occurred during sea-level low stands, when the western PIS covered most of the Chilean fjords, which today retain glaciofluvial sediments. During these intervals, high-amplitude phases of enhanced sediment supply occur at millennial timescales, reflecting increased ice discharge most likely due to a growing PIS. We assign the late MIS 3 to MIS 2 phases and, by inference, older advances to Antarctic cold stages. We conclude that the increased sediment/meltwater release during Southern Hemisphere millennial-scale cold phases was likely related to higher precipitation caused by enhanced westerly winds at the northwestern margin of the PIS. Our records complement terrestrial archives and provide evidence for PIS climate sensitivity.

The influence of fluvial and glacial watershed dynamics on Holocene sediment accumulation in Cariboo Lake, Columbia Mountains, British Columbia, Canada

Records of sedimentation collected from Cariboo Lake, situated in the northern Columbia Mountains, British Columbia, Canada, are analyzed to assess Holocene fluvial and glacial watershed dynamics. The aim of this study is to provide a proxy record of Holocene hydroclimate and glacier change from sediment archives at a higher temporal resolution compared to available records for the Interior Ranges of British Columbia. Deglacial and Holocene sediment accumulation is observed to reach a maximum thickness of 35 m in deep parts of the lake, using sub-bottom acoustic soundings. A transition from massive to well-stratified sediments is observed in the sub-bottom acoustic record during final phases of valley deglaciation in the region (~10.5–9 cal ka BP). Laminae couplets are interpreted to be deposited annually according to two 14C dates and a varve counting chronology. Two long cores, 2.9 and 3.8 m in length, were selected for analysis with estimated basal dates of 2 cal ka BP. Trends in downcore sediment characteristics were linked to environmental changes in the glaciated catchment headwaters at a temporal resolution of ~100 years. Upstream lake filtering of river floodplains and lakes prevented finding a higher temporal resolution linkage between the sediment characteristics and headwater fluvial and glacial activity. Despite some upstream filtering, the Cariboo River was found to be the primary source of sediment to the long core sites. Observed grain size and varve thickness from two long cores show above average trends, which are coincident with cooler temperatures and the primary glacier advances over the last 2 ka.

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 &gt;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.

Reconstruction of glaciers in the western boundary of the Altiplano (18.5°-19°S): Singularities and insights on potential drivers of past advances

Today, glaciers in the western Altiplano are very scarce, even on peaks exceeding 6000 m. In this mostly ice-free landscape, however, moraines and other glacial deposits are commonly found attesting to quite different climate conditions that favored the advance of glaciers in the past. Although other areas of the Altiplano have been commonly accounted for regarding paleoclimate reconstructions, western Altiplano has been often overlooked. Here we present a detailed map of glacial landforms and a paleoglacier reconstruction from a test area in the western Altiplano between 18.5° and 19°S. We reconstructed regional equilibrium line altitudes (ELA) for several moraine stages, representing extensive past glacier advances in the region. During a prominent and ubiquitous ‘Principal Moraine (PM)’ stage glaciers from most peaks and all orientations advanced to altitudes of up to 4000 m asl. Reconstructed PM ELAs along 90 valleys range from 4400 to 5000 m asl. ELA distribution reveals a strong aspect-dependency at the western boundary of the Altiplano, with ELAs 300 m lower on west-facing glaciers than east-facing glaciers. The coincidence of such steep gradient with a prominent NW-SE ridge accounts for topographic control on the precipitation and thus in the advance of glaciers along the western boundary of the Altiplano. To the east, ELAs from the peaks towering the Altiplano are comparable to ELAs from east-facing glaciers at the western Altiplano boundary but show little to no aspect-dependency. Since these patterns cannot be solely explained by increased moisture advection from the Amazon basin, we suspect that western-sourced moisture associated with increased frequency of cold fronts and cut-off events played an important role in the glacier dynamics at this latitude. Nevertheless, further investigations are required to evaluate the relative role of both precipitation regimes on the glacier dynamics from the westernmost Altiplano.

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.

Mid-Holocene climate-glacier relationship inferred from landforms and relict lake sequence, Southern Zanskar ranges, NW Himalaya

The geomorphological disposition of (para/peri) glacial landforms, elemental geochemistry, and optical chronology of the relict lake sediment in the Southern Zanskar ranges, northwest Himalaya are used to understand the relationship between glacial dynamics and the lake sedimentation during the mid-Holocene climate variability. Following the Last Glacial Maxima (LGM), pulsating deposition of outwash gravels until the early Holocene overwhelmed the Zanskar valley. The obstruction of Tsarap Chu (chu = river) by alluvial fans during the mid-Holocene led to the development of Padum Lake. In the present study, cirque glacier moraines representing three minor glacial advances were mapped along with sedimentological details and dated using Optically Stimulated Luminescence (OSL) dating technique. The oldest cirque glacier advance - Padum Cirque moraine-3 (PDCm-3) is dated to 11.4 ± 0.9 ka. The succeeding advance (PDCm-2) is dated to 5.3 ± 0.6 and 4.8 ± 0.8 ka whereas, the younger cirque glacier advance (PDCm-1) remains undated. The mid to late Holocene climate variability inferred using major and trace element geochemistry of the relict Padum lake sediments supported by optical chronology indicates six centennial to millennial-scale climatic phases. The prominent warmer phases are represented by decreased mineralogical fine grain flux (low K/Ti, Fe/Si, and Al/Si) with a corresponding increased coarse grain flux (higher Ti/Al and Sr/Al ratios). These phases are dated between 5.9 and 5.5 ka (phase-I), 3.8 and 3.4 ka (phase-IV), and 2.8 and 2.5 ka (phase-VI). The increased mineralogical finer fraction (higher K/Ti, Fe/Si, and Al/Si) between 5.5 and 5.1 ka (phase-II) and 3.4 and 2.8 ka (phase-V) indicate reduced meltwater flux during cooler phases. The intervening phase-III (5.1–3.8 ka) is characterized by increased mineralogical coarse grain flux (decreasing K/Ti, Fe/Si, Al/Si) suggesting gradual warming. The oscillatory climate at millennial scale was further used to understand glacier dynamics. The PDCm-2 advance in the lake record corresponds to the first major cooling (5.5 and 5.1 ka; phase-II) and continued until ∼3.8 ka. Using geochemical data of lake record, a major recession is inferred after 3.8 ka that persisted until around 3.4 ka (phase-IV). Similarly, the undated younger cirque glacier advance (PDCm-1) is assigned to the second cooling event (3.4 and 2.8 ka; phase-V). Thereafter, the cirque glaciers receded, most likely under increasing dryness and fluctuating climate (2.8–2.5 ka, phase-VI). After ∼2.6 ka, the development of ice-wedge pseudomorphs indicates the onset of permafrost conditions that degraded after ∼2.5 ka implying an increase in air temperature. The lake sedimentation terminates with the deposition of multiple younger alluvial fan facies. The climate variability shows a close correspondence with regional climate records suggesting that marginal glacier advancements were triggered by enhanced moisture via atmospheric rivers and cooler winter temperatures. The study highlights the potential of relict lake sediment in association with para- and peri-glacial landforms to reconstruct the pattern of minor glacier responses to climate variability during the Holocene.

Late Quaternary glacier advances in the Andes of Santiago, central Chile, and paleoclimatic implications

Andean mountain glaciers in central Chile are in a transitional zone between the seasonal influence of the mid-latitude westerlies and subtropical semiarid conditions to the north. Long-term glacial dynamics for these glaciers and their relationship with the paleoclimate during the late Quaternary are poorly known despite their relevancy. We estimate here the timing and extent of late Pleistocene–early Holocene glaciers in the Andes of Santiago (33°50′S) from geomorphological and geochronological analyses. Our observations evidence that a glacial stage occurred before the Last Glacial Maximum (ELGM) at the San Gabriel drift (1,300 m a.s.l.), dated as ∼46–36 ka. Glacial stages during the latest Pleistocene–early Holocene transition period, partially concomitant with the Antarctic Cold Reversal (ACR) and with the Younger Dryas (YD) chronozones, were identified and dated at La Engorda drift (2,450–2,570 m a.s.l.) at ∼15–10 ka. We propose that the San Gabriel drift represents a prolonged glacial advance driven by increased precipitation and cold conditions off central Chile during glacial times. In La Engorda drift, late glacial advances occurred associated with increased regional precipitation, in the context of a transition from humid to arid climate in central Chile, concomitantly with a general warming trend of sea surface temperatures offshore in the southeastern Pacific and with reduced austral summer insolation. The results support the sensitivity of the Andean mountain glaciers to precipitation and paleoclimate conditions, most possibly associated with periods of increased northward influence of the mid-latitude westerlies during glacial and late glacial times, in addition to the El Niño/Southern Oscillation (ENSO) impact since the mid-Holocene, driving late Quaternary glacier advances in central Chile. We estimate a maximum variation of ∼1,200 m in the position of the late Quaternary Equilibrium Line Altitude (ELA), inferred at ∼3,400 m and ∼3,600 m a.s.l. at the time of the San Gabriel and La Engorda drifts, respectively, with respect to its modern location close to 4,600 m a.s.l.

Spatially coherent variability in modern orographic precipitation produces asymmetric paleo-glacier extents in flowline models: Olympic Mountains, USA

Abstract. Glaciers are sensitive to temporal climate variability. Glacier sensitivity to spatial variability in climate has been much less studied. The Olympic Mountains of Washington state, USA, experience a pronounced orographic precipitation gradient, with modern annual precipitation ranging between ∼6500 and ∼500 mm water equivalent. In the Quinault valley, on the wet side of the range, a glacier extended onto the coastal plain, reaching a maximum position during the Early Wisconsin glaciation. On the dry side of the range, in the Elwha valley, there is no evidence of a large paleo-glacier during the Wisconsin glaciation. We hypothesize that asymmetry in the past glacier extent was driven by spatial variability in precipitation. To evaluate this hypothesis, we constrain the past precipitation gradient and model the glacier extent. We explore variability in observed and modeled precipitation gradients over timescales from 6 h to ∼100 yr. Across three datasets, basin-averaged precipitation in the Elwha is 54 % of that in the Quinault. Our analysis overwhelmingly indicates spatially coherent variability in precipitation across the peninsula. We conclude that the past precipitation gradient was likely similar to the modern gradient. We use a one-dimensional glacier flowline model, driven by sea level summer temperature and annual precipitation to approximate the glacier extent in the Quinault and Elwha valleys. We find several equilibrium states for the Quinault glacier at the mapped maximum position within paleoclimate constraints for cooling and drying, relative to present-day conditions. Assuming stable precipitation gradients, we model the Elwha glacier extent for the climates of these equilibria. At the warm end of the paleoclimate constraint (July average sea level temperature of 10.5 ∘C), a small valley glacier occurs in the high headwaters of the Elwha valley. Yet, for the cooler end of the allowable paleoclimate (July average sea level temperature of 7 ∘C), the Elwha glacier advances to a narrow notch in the valley, thickens, and rapidly extends far beyond the likely true maximum extent. Therefore, we suggest that the Early Wisconsin period was more likely to have been relatively warm because our models of the glacial extent are consistent with the past record of glaciation in both the Quinault valley and Elwha valley for warm conditions but inconsistent for cooler conditions. Alternatively, spatially variable drivers of ablation, including differences in cloudiness, could have contributed to past asymmetry in the glacier extent. Future research to constrain past precipitation gradients and evaluate their impact on glacier dynamics is needed to better interpret the climatic significance of past glaciation and to predict the future response of glaciers to climate change.

First &lt;sup&gt;10&lt;/sup&gt;Be dates of Late Holocene moraines of the Kashkatash and Irik glaciers, Northern Caucasus

We present 11 10Be ages of the moraines of the Irik and Kashkatash glaciers that allowed identifying and dating several Late Holocene glacier advances for the first time, including a prominent advance exceeding the Little Ice Age (LIA) maximum that occurred at 1.6–1.7 ka at еру Irik Glacier. The advance is dated by the three very close 10Be ages of a moraine (1.57 ± 0.23 ka, 1.63 ± 0.23, and 1.68 ± 0.24 ka) located in the vicinity of the moraines of the Little Ice Age (LIA) maximum advance. The advance that occurred at 1.6–1.7 ka might be a possible analogue of the “Historical” stage described earlier in the Caucasus in literature basing at geomorphic evidence, speculations, and analogues with other mountain regions, but not dated. Another possibility is a potential correlation of this advance with the Late Antique Little Ice Age cooling in 536 to ~660 CE. The age of Irik Glacier advance is close to the humid period identified in the Garabashi (Baksan, Elbrus valley) lake sediments at 1500–1700 years BP. The magnitude of the identified glacier advances over the past two millennia was similar. Between the advance of 1.6–1.7 ka and the position of the glacier in 2022 CE the elevation of the Irik Glacier front increased by 520 m from 2490 to 3010 m asl. Four 10Be dates (0.7 + 0.11, 0.72+0.11, 0.77 + 0.11 and 0.82 + 0.18 ka) of the lateral moraine of the Kashkatash Glacier constrain the advance of the first stage of the LIA. The advance of the 13th century is also dated by 10Be at the Donguz-Orun and Chalaati glaciers located at the Northern and Southern slopes of the Caucasus, respectively. The corresponding cooling in ca 1250–1400 CE is identified in the sedimentary paleoclimatic proxies of Lake Karakel (Teberda valley). A later advance at the Kashkatash Glacier is constrained by only one 10Be date (0.53± 0.13 ka) and needs further confirmation. Till deposited between the 1490s and 1640s at the Greater Azau Glacier is close to the date of this advance of the Kashkatash Glacier. A cooling at that time is recorded in the proxies of Karakel Lake sediments (1500–1630 CE). Three other 10Be dates of two earlier advances at 0.25 + 0.04 ka and between 0.14 + 0.03 and 0.16 ± 0.02 ka at Kashkatash Glacier are indirectly supported by tree-ring, lake sediment, 14C, and historical data. Further research and new data is necessary to increase the credibility and accuracy of the dates of glacier advances of the Late Holocene in the Northern Caucasus.

Climatic and topographic controls on glacial changes (1973-2020) in Shigar Basin, Central Karakoram, Northern Pakistan.

The Hindukush, Karakorum, and Himalaya (HKH) mountains are often referred to as the "Third Pole" because of high snow, being a major freshwater resource and early indicator of climate change. Therefore, research on the dynamics of glacier changes and their relationship with climate and topographic variability is essential for sustainable water resource management and adaptation strategies in Pakistan. In this contribution, we delineated 187 glaciers and examined these glacier changes in the Shigar Basin from 1973 to 2020 using Corona, Landsat Operational Land Imager/Enhanced Thematic Mapper Plus/Thematic Mapper/Multispectral Scanner System (OLI/ETM/TM/MSS), Alaska Satellite Facility (ASF), and Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) imageries. The total glacier area decreased from 2796.31 ± 132 km2 in 1973 to 2756.27 ± 63 km2 in 2020 at an average rate of - 0.83 ± 0.03 km2yr-1. Specifically, during the period of 1990-2000, these glaciers shrank most heavily at an average rate of - 2.372 ± 0.08 km2yr-1. In contrast, an increased rate of 0.57 ± 0.02 km2yr-1 in total glacier area was observed during the recent decade (2010-2020). Moreover, the glaciers with gentle slopes retreated less heavily than the steep ones. There was reduction in glacier coverage and length for all slope classes, and a small reduction was observed with gentle slopes, while higher losses were observed on steep slope gradients. The transition of glaciers in the Shigar Basin may be attributed by the direct influence of glacier size and topographical characteristics. By comparing with climate records, our findings suggest that the overall reduction in glacier area from 1973 to 2020 was associated with declining precipitation (- 0.78 mmm/year) and rising temperature (0.045°C/year) trends in the region, and glacier advances in recent decade (2010-2020) were likely to be driven by increased winter and autumn precipitation.

Unraveling the climate control on debris-free glacier evolution in the Everest region (Nepal, central Himalaya) during the Holocene

Current mass balance and meteorological surveys of Mera glacier located about 30 km south of Mount Everest in Nepal show the dominant role of Asian monsoon precipitation on interannual mass balance variability while temperature controls the altitude of snow-rain threshold. As these observations on mass balance variability only explore the recent decades, studies on paleo glacial extents are useful to investigate the long-term climate forcing on glacier evolution. To do so, we investigated the long-term evolution of the debris-free Mera glacier and a neighbouring small debris-free South Khare glacier. Fifty-one 10Be CRE ages were obtained from samples collected on moraine boulders and roches moutonnées. 10Be CRE ages of the boulders span from the end of the Lateglacial (19.0–11.7 ka) to the Little Ice Age (∼0.6–0.1 ka). The oldest dated moraine in this study was observed at the base of South Khare glacier with an age of 13.6 ± 0.5 ka. The two glaciers subsequently experienced their largest Holocene extent in the Early Holocene with moraines dated to 11.0 ± 0.3 ka at the base of Mera glacier and 10.8 ± 0.5 ka at the base of South Khare glacier. We did not observe any moraine from the Mid-Holocene. During the Late Holocene several glacier advances were recorded around 2.3 ± 0.2 ka, 1.5 ka and then during the last centuries at Mera glacier and around 2.8 ± 0.6 ka, and during the Little Ice Age at South Khare glacier. To explore the links between long-term Nepalese glacier changes and climate, we used oceanic and terrestrial Indian Summer monsoon reconstructions and temperature and precipitation output from two transient global climate models TraCE and LOVECLIM. These climate data outputs were corrected by a reconstruction of the Atlantic Meridional Overturning Circulation (AMOC) over the Holocene and its associated climatic impacts. We also used sensitivity experiments from the IPSL (Institut Pierre Simon Laplace) model to discuss the possible influence of horizontal resolution, land hydrology, vegetation and runoff on changes in Asian summer monsoon. Importantly, we show this long-term Nepalese glacier pattern does not perfectly conform neither to the Indian monsoon precipitation that is documented from terrestrial and marine records nor to temperature and precipitation changes simulated by the models. While the maximum glacier extent in the Early Holocene corresponds to enhanced precipitation documented by proxies and models, the Late Holocene glacier advance remains puzzling. We claim that new paleo glacier records and improved climate simulations are necessary to get a better understanding of past glacier changes and the associated climate dynamics, which might be crucial to gain confidence in both glacier and climate future evolutions.