Glacier Advances Research Articles

Sudden glacier advances in the Cachapoal Valley, Southern Central Andes of Chile (34°S)

Throughout the Andes Mountains of South America, a general trend of glacier shrinkage has taken place in modern times. However, a few glaciers have undergone considerable temporally advances or even surged during the mid-19th to 20th century CE. These valley glaciers are mainly located in the Central Andes of Chile and Argentina. The research presented here focuses on the changes of the Cachapoal Glacier in the Southern Central Andes of Chile. Spectacular glacier advances occurred at least three times in historical times, which lead to river blockages and successive lake outburst floods. The glacier advances were reconstructed with a multi-method approach including geomorphological mapping, 10Be cosmogenic exposure dating of moraines, multi-temporal comparison of historical and recent photographs and paintings as well as the interpretation of aerial photographs and satellite images and the analysis of early travel reports. The article highlights the diversity of environmental conditions for the formation of glaciers in terms of the topographical and climatic setting and the resulting distinct glacier behavior along the Andes Mountains. It is argued for the Cachapoal Glacier that the glacier advances are intrinsic to the glacier type and may not be necessarily climate-dependent. This is characteristic for avalanche-fed glaciers of which the glacier dynamic is strongly controlled by the topographic setting and sudden inputs of ice and rock avalanches as well as by the specific debris transfer system and hydrological drainage pattern. At the regional level, the fluctuations of the Cachapoal Glacier are compared with glaciers of neighboring mountain ranges in the Southern Central Andes and at the global scale with those of the Karakoram Mountains in High Asia with a similar dynamic glacier behavior.

Modelado numérico de las oscilaciones frontales y ocurrencia de formación de diques de hielo del Glaciar Perito Moreno, Campo de Hielo Patagónico Sur

En el presente estudio, se aborda el diseño y desarrollo de un modelo numérico computacional del comportamiento del ciclo oscilatorio estacional de avance y retroceso del glaciar Perito Moreno, denominado MO-ACAR. Dentro de su comportamiento oscilatorio, en algunos años el glaciar avanza y alcanza la Península de Magallanes formando un dique de hielo. Por ello, el objetivo del MO-ACAR es simular la posición frontal diaria del glaciar y la ocurrencia de eventos de formación de los diques de hielo durante el periodo 1994-2018. El modelo fue calibrado y validado a partir de un proceso de optimización iterativo, basado en la maximización de valores de correlación y minimización de errores de distancia. La simulación de la ocurrencia de la formación de diques de hielo y la oscilación de la posición frontal lograron altas prestaciones, alcanzando óptimos valores de correlación (0,99) y bajos errores de posición (9,56 ± 13,94 m), respectivamente. Los resultados demuestran que la dinámica del glaciar y la formación de los diques de hielo responden a distintas escalas temporales. En periodos cortos-intermedios de tiempo (escalas diarias-estacionales), la ocurrencia depende tanto de las características propias del evento, como de la fase e intensidad del evento previo. En periodos prolongados (escalas mayores a un año), la modulación de baja frecuencia de la velocidad del flujo de hielo, provocada por las variaciones de temperatura del aire, controla los periodos con formación de diques de hielo y libres de éstos.

Climates since late quaternary glacier advances: Glacier-climate modeling in the Kunlun Pass area, Burhan Budai Shan, northeastern Tibetan Plateau

The quantitative reconstructions of past climate changes on the Tibetan Plateau derived from glacial record based on glacier-climate models have been reported in existing researches. However, compared with low altitude areas and the vast majority parts of the Tibetan Plateau, modeled paleoclimate conditions from glacial record are still lack. This hampers the advancing understanding of regional climate–glacier interactions. The glacial history of Burhan Budai Shan provides an opportunity to reconstruct paleoclimate conditions since the penultimate glacial cycle. We applied a coupled mass balance and ice flow model to estimate paleoclimate during the early Holocene, MIS3 and penultimate glacial cycle. On the southern model domain, the model results suggested that the temperature drops ranged from -0.5～0.1 °C and 2.4～3.9 °C with precipitation being 140～200% and 30～100% of present during the MIS3 and penultimate glacial cycle, respectively. On the northern model domain, the early Holocene temperature was lower than present levels by 0.5～1.5 °C which presented separate evidence for the early Holocene precipitation being 80～150% of modern values. The model results in the model domain are generally consistent with other climate records on the Tibetan Plateau.

Dynamics of Dalk Glacier in East Antarctica Derived from Multisource Satellite Observations Since 2000

Monitoring variability in outlet glaciers can improve the understanding of feedbacks associated with calving, ocean thermal forcing, and climate change. In this study, we present a remote-sensing investigation of Dalk Glacier in East Antarctica to analyze its dynamic changes. Terminus positions and surface ice velocities were estimated from Landsat and Sentinel-1 data, and the high-precision Worldview digital elevation model (DEM) was generated to determine the location of the potential ice rumple. We detected the cyclic behavior of glacier terminus changes and similar periodic increases in surface velocity since 2000. The terminus retreated in 2006, 2009, 2010, and 2016 and advanced in other years. The surface velocity of Dalk Glacier has a 5-year cycle with interannual speed-ups in 2007, 2012, and 2017. Our observations show the relationship between velocity changes and terminus variations, as well as the driving role of the ice rumple. Ice velocity often increases after calving events and continuous retreats. The loss of buttressing provided by an ice rumple may be a primary factor for increases in ice velocity. Given the restriction of the ice rumple, the surface velocity remains relatively stable when the glacier advances. The calving events may be linked to the unstable terminus caused by the ice rumple.

Neodymium isotope constraints on chemical weathering and past glacial activity in Svalbard

Neodymium (Nd) isotopes in leached authigenic components of marine sediments have been increasingly used as a tracer of past ocean-water masses. Despite the general assumption that the Nd isotopic composition of solutes released during chemical weathering fingerprints the source rocks on continents, preferential dissolution of easily dissolvable phases may result in significant deviations in Nd isotopic composition between the solutes and the source rocks, with potential implications for the utility of Nd isotopes in paleoenvironmental studies. Here, we present the Nd isotopic compositions of leached and detrital fractions separated from bedrock and marine sediment samples from the Svalbard archipelago. Our goal is to further understand the behaviour of Nd isotopes during chemical weathering in glacial catchments and evaluate how glacier fluctuations and associated weathering congruency may have affected the export of dissolved Nd isotope signatures to seawater.Our results confirm that terrestrial weathering on Svalbard causes considerable Nd isotopic decoupling between the leached and detrital fractions of fjord sediments (△εNd), resulting from the preferential dissolution of marine precipitates in glaciated catchments dominated by sedimentary rocks. We also show that the degree of Nd isotopic decoupling has fluctuated in response to climate variability on Svalbard during the Holocene, which is also as suggested by the occurrence of generally higher △εNd values during periods of glacier advances in sediment cores retrieved from two different fjords (Dicksonfjorden and Woodfjorden). We posit that the high △εNd values can be ascribed to incongruent chemical weathering of fresh rock flour produced by glacial abrasion. This finding suggests that the degree of Nd isotopic decoupling could be used as a new proxy for tracing glacial fluctuations and associated glacier-derived nutrient inputs to the marine realm.

Chronology and climate sensitivity of the post‐LGMglaciation in the Dunagiri valley, Dhauliganga basin, Central Himalaya, India

In this study, we reconstruct the style and timing of the late Quaternary glaciation pattern in a monsoon‐influenced precipitation‐deprived region (Dhauliganga basin) of the Central Himalaya, India. We present detailed glacial geomorphological mapping, aided by topographic maps, satellite data, Google Earth images, global positioning system survey, and fieldwork (2012–2016), supported by optically stimulated luminescence dating. Our estimations for the magnitude and timing of glaciations in the Dunagiri Glacier valley suggest five sets of glacial advances. The oldest and most extensive glaciation in the valley is Dunagiri Glacial Stage‐I (DGS‐I), represented by a discontinuous moraine ridge that extends down to ~10 km (~2700 m a.s.l.) from the present‐day snout and formed 13±3 ka ago. TheDGS‐IIstage is present in the form of a small moraine ridge (~3000 m a.s.l.) that formed 10±2 ka ago. TheDGS‐IIIandDGS‐IVglacial stages are 5–6 and 3.5 ka old, respectively. The youngest stage (DGS‐V) of glaciation belongs to the neoglaciation episode ~1 ka old.DGS‐I was the most extensive glaciation in the valley and corresponds to the global Last Glacial Maximum. The glaciation pattern has been correlated with the estimates of present‐day glacial sensitivity to climate and explained as forcing factors sensitive to temperature and/or precipitation changes in the region. The observations based on prevailing climate correlations aided with available glacial chronologies underline the fact that the glacial valleys situated in precipitation‐deprived regions have preserved a delayed response of glaciations to regional climatic events. Estimates for the timing and pattern of glaciation in the present study suggest a different glacial response for modern climatic changes than previously assumed. We suggest that individual glacier advances differ regionally and, therefore, should not be interpreted as being reflective of a change in the whole geographical belt.

Late-glacial to Holocene glaciers in the Turkish mountains

Although Turkey is a mid-latitude country, because of its relatively high topography it hosted Quaternary glaciers on its mountains. Some of these high mountains (> 3500 m above sea level) still contain recent glaciers, probably remnants of Holocene glacier advances. Despite the abundance of recent cosmogenic surface exposure dating studies in Turkey, Holocene glacial chronologies are still limited. Here, we reviewed five mountains in Turkey where Holocene chronologies were presented in earlier studies. All these glacial chronologies are located in the western and central Taurus Mountain Ranges and in central Anatolia. The timing of the glaciations has been established mainly by cosmogenic 36Cl surface exposure dating. We re-calculated some of the published cosmogenic ages using up-to-date production rates and scaling schemas. The maximum extent of glaciers was during the Last Glacial Maximum (c. 21 ka), but Late-glacial (c. 16 ka) and Younger Dryas (c. 12 ka) ages were also reported. At the onset of the Holocene (c. 11 ka), glaciers retreated to less extensive positions and deposited their moraines. Contemporaneously, periglacial and paraglacial processes also became active with the development of rock glaciers in several parts of the country. Some mountains still contain active glaciers although the melting tendency is obvious as in other parts of the world. Considering the paleoglacial/glacial regions in Turkey, there are numerous areas that do not have their own glacial chronologies and further studies should focus on these undated regions.

Latest Pleistocene glacier advances and post-Younger Dryas rock glacier stabilization in the Mt. Kriváň group, High Tatra Mountains, Slovakia

The timing of glacier disappearance and rock glacier stabilization in the highest massifs of the Carpathians is still poorly documented. In this paper, we establish the extent and chronology of the final stages of glaciation and timing of stabilization of the uppermost rock glaciers in the Tatra Mountains, which are the highest (2654 m a.s.l.), northernmost (N 49°12′), and coldest range in the Carpathians. On the base of morphostratigraphic principles, Schmidt Hammer tests and glacier equilibrium line altitude (ELA) estimation, we assigned moraines and rock glaciers in the Mt. Kriváň massif (SW part of High Tatras) to a threefold stratigraphic sequence with glacial stages/advances from older to younger: Popradské pleso (Pp), Suchá važecká I (Sv I) and Suchá važecká II (Sv II). Landforms attributed to two younger advances, Sv I and Sv II, were sampled for the purpose of cosmogenic 10Be surface exposure dating. Our data show that Pp and Sv I glacial advances occurred during the Oldest Dryas climatic downturn. The younger advance (Sv I) occurred just before the Bølling-Allerød (B/A) warming at 14.9 ± 0.4 ka, at this time small glaciers occupied lower glacial cirques in the study area. The youngest Sv II advance was characterized by rock glaciers and small debris-covered glaciers confined to the highest cirques. The mean exposure age of four relict rock glaciers of this stage is 11.1 ± 0.9 ka but individual rock glacier mean ages spanned between 11.8 and 10.4 ka. Our research results show that the youngest moraines and rock glaciers in the Tatra Mountains were formed during the Younger Dryas (YD), but the final permafrost melting and rock glacier stabilization period was delayed until the early Holocene, but no later than 10.4 ka. In high elevation cirque bottoms (up to 2120 m a.s.l.), the YD glaciers and rock glaciers readvanced across land which was ice-free as early as 14.8–14.2 ka. Thus, it is likely that during the B/A interphase, glaciers completely disappeared in the Tatra Mountains. The YD was the last period of glacial/periglacial activity in the massif. As we investigated one of the highest-situated rock glaciers in the Tatras (up to 2220 m a.s.l.), we conclude that all rock glaciers in this massif are relict landforms which developed in response to severe Lateglacial climate conditions. The Lateglacial climate of the Tatra Mountains is discussed herein on the basis of glacier equilibrium line altitude (ELA) estimation and the vertical distribution of rock glacier belts. We argue that paleoclimate significance of the presented geomorphological record may match paleobotanical proxy reconstructions and the results of climate simulations, but only if the impact of enhanced temperature seasonality on glacier mass balance and rock glacier activity is taken into account.

Glacier fluctuations during the Late Glacial and Holocene on the Ariège valley, northern slope of the Pyrenees and reconstructed climatic conditions

The glacier evolution from two valleys located near Vicdessos, French Pyrenees, is deciphered from 17 in situ cosmic ray exposure (CRE) dating. In the Picot valley, Late Glacial glacier advances were documented during Heinrich Stadial 1 (HS1), while a rock glacier developed or was reactivated during the mid-Holocene. In the upper Medecourbe valley, the largest visible ice extent occurred during the Younger Dryas (YD) or earlier. At least two moraines formed during the early Holocene were dated, while an undated moraine located close to the head of the catchment may have been formed either during the Late Holocene or the Little Ice Age. A mass balance model suggests that a temperature about 5.1 °C cooler than today, without precipitation change, would be necessary to form a moraine at the base of the Picot catchment during HS1 at 2000 m a.s.l. A temperature about 3.9 °C cooler than today is necessary to explain a moraine formed during the Late Glacial–YD transition at Medecourbe at 2200 m. Comparing CRE dating from Picot and Medecourbe with those in the Pyrenees and the Alps highlights original glacial patterns. In the Picot catchment whose summit is below the current regional ELA, the absence of YD and Late Holocene moraines is consistent with the general low-altitude deglaciation trend documented in the northern and southern slope of the Pyrenees, but differs from high-altitude Pyrenean and Alpine records. However, due to specific geomorphological conditions, the glacial evolution of the Medecourbe valley took place differently compared to other low-altitude catchments in the Pyrenees.

Rock glacier characteristics serve as an indirect record of multiple alpine glacier advances in Taylor Valley, Antarctica

Abstract. The geomorphic record indicates that alpine glaciers in the McMurdo Dry Valleys of southern Victoria Land, Antarctica, appear to advance during interglacial periods in response to ice-free conditions in the Ross Sea. Few records of these advances are preserved and/or subaerially exposed, complicating the interpretations of regional glacier response to climate changes. Here, we present geophysical and geochemical analyses of a rock glacier that originates from icefalls fed by alpine Doran Glacier in central Taylor Valley. The rock glacier exhibits a trend of increased weathering of granitic clasts via ventifaction and grussification down-flow. Meltwater ponds on the rock glacier exhibit variable salinity that ranges from freshwater to higher than seawater, with the highest salinity pond near the rock glacier toe. Ground-penetrating radar analyses reveal the feature to possess a primarily clean ice interior, with layers of englacial debris. Stable isotopic data from three ice cores support a glacial origin for the ice within the rock glacier. These data suggest that the current morphology of the rock glacier is the result of multiple events of increased ice contribution caused by advances of Doran Glacier, which is the main source of ice to the rock glacier. We therefore demonstrate the potential of ice-cored rock glaciers to record multiple advances and retreats of Dry Valley glaciers, permitting the interpretation of glacial responses to Pleistocene and Holocene climate change even where direct records are not present.

Redefining the timing of Tongul glacial stage in the Suru valley, NW Himalaya, India: New insights from luminescence dating

The present study investigates latero-frontal moraines to reconstruct the pattern of glacier advances and associated climate variability in the Suru valley, southwestern Zanskar Himalaya. Impressive sets of latero-frontal moraines and discontinuous morainic ridges (recessional) represent the records of the past glacier advance and retreat. The northerly trending latero-frontal moraines that descend down the tributary valleys and terminate at the trunk Suru valley are the geomorphic expression of one of the oldest preserved record of glacier advance and is named as Tongul glacial stage. Previous studies (based on 10Be and 14C ages) defining the chronology of Tongul glacial stage are either limited in number (14C ages) or have a large spread (10Be ages) and hence demand further investigation. Optically stimulated luminescence (OSL) dating suggests that the Tongul glacial stage responded to the global last glacial maximum (gLGM) dated between ~20 and 24 ka. We suggest that the Tongul glacial stage was driven by enhanced mid-latitude westerlies and reduced temperature (viz., continental cooling) during MIS 2 and facilitated by corresponding long winters.

+A 5680-year tree-ring temperature record for southern South America

It is widely documented that the Earth’s surface temperatures have increased in recent decades. However, temperature increment patterns are not uniform around the globe, showing different or even contrasting trends. Here we present a mean maximum summer temperature record, based on tree-ring widths, over the past 5682 years (3672BC – 2009AD) for southern South America (SSA), covering from mid-Holocene to the present. This is the longest such record for the Southern Hemisphere (SH), and expands available annual proxy climate records for this region in more than 2060 years. Our record explains 49% of the temperature variation, and documents two major warm periods between 3140–2800BC and 70BC – 150AD, which coincide with the lack of evidence of glacier advances in SSA. Recent decades in the reconstruction (1959–2009) show a warming trend that is not exceptional in the context of the last five millennia. The long-term relationship between our temperature reconstruction and a reconstructed total solar irradiance record, with coinciding cycles at 293, 372, 432–434, 512 and 746 years, indicate a persistent influence of solar forcing on centennial climate variability in SSA. At interannual to interdecadal scales, reconstructed temperature is mainly related to the internal climate variability of the Pacific Ocean, including El Niño Southern Oscillation (ENSO) and longer oscillations. Our study reveals the need to characterize regional-scale climate variability and its drivers, which in the context of global-scale processes such as anthropogenic warming, interact to modulate local climate affecting humans and ecosystems.

Optical chronology and climatic implication of glacial advances from the southern Ladakh Range, NW Himalaya, India

Morphological, sedimentological, and chronological evidence suggests the preservation of three glacial advances of decreasing magnitude in the Puche valley (near Leh), southern Ladakh Ranges. The oldest moraine of Puche Glacier Advance-1 (PGA-1) is optically dated to the early Marine Isotopic Stage (MIS)-2 (31.5 ± 3.3 ka) that persisted until around the global Last Glacial Maxima (LGM) (22.7 ± 1.6 ka). The PGA-2 is optically dated to the post LGM (14.4 ± 1.0 ka) and perhaps was triggered by meltwater pulse (1a?) cooling. The youngest PGA-3 remains undated and could be of Holocene age. The Optically Stimulated Luminescence (OSL) ages suggest a greater role of westerlies in driving the glacier advances during the MIS-2 in the southern Ladakh Ranges and are at variance with the previous suggestions that recommended monsoon driven glacier advances. The OSL ages compared to the previously obtained 10Be surface exposure ages are younger by a magnitude. The study explores probable causes for the variance in two chronologies and suggests employing multiple dating methods to minimize the uncertainty both in terms of age and climatic interpretation.

The changing extent of marine-terminating glaciers and ice caps in northeastern Svalbard since the ‘Little Ice Age’ from marine-geophysical records

Climate warming in Svalbard since the end of the ‘Little Ice Age’ early in the 20th century has reduced glacier extent in the archipelago. Previous attempts to reconstruct ‘Little Ice Age’ glacier limits have encountered problems in specifying the area of tidewater glacier advances because it is difficult to estimate the past positions of their marine termini. Multibeam echo-sounding data are needed to map past glacier extent offshore, especially in open-marine settings where subaerial lateral moraines cannot be used due to the absence of fjord walls. We use the submarine glacial landform record to measure the recent limits of advance of over 30 marine-terminating northeastern Svalbard glaciers and ice caps. Our results demonstrate that previous work has underestimated the ice-covered area relative to today by about 40% for northeastern Svalbard (excluding southeast Austfonna) because marine-geophysical evidence in the form of submarine terminal moraines was not included. We show that the recent ice extent was 1753 km2larger than today over our full area of multibeam data coverage; about 5% of the total modern ice cover of Svalbard. It has often been assumed that moraine ridges located within a few kilometres of modern ice fronts in Svalbard represent either a ‘Little Ice Age’ maximum or relate to surge activity over the past century or so. In the marine environment of northeastern Svalbard, this timing can often be confirmed by reference to early historical maps and aerial photographs. Assemblages of submarine glacial landforms inshore of recently deposited terminal moraines suggest whether a recent advance may be a result of surging or ‘Little Ice Age’ climatic cooling relative to today. However, older terminal moraines do exist in the archipelago, as shown by radiocarbon and10Be dating of Holocene moraine ridges.

Investigating the sensitivity of glaciers to climate variability since the MIS-2 in the upper Ganga catchment (Saraswati valley), Central Himalaya

Moraines, outwash gravel terraces, fluvial drapes and lacustrine sequences are used to infer the pattern of glacial fluctuations in the Saraswati valley (upper Ganga catchment). Located in transitional climatic zone between dry steppe of the Tibetan plateau in the north and sub-humid higher Himalaya in the south, the Saraswati valley has preserved evidence of four glacier advances. These are identified as the Saraswati Glacial Stage (SGS)-1 (oldest) to SGS-4 (youngest). Based on the relative dating and luminescence ages obtained on younger advances, the SGS-1 is ascribed to pre-Marine Isotopic Stage (MIS)-2. The SGS-2 is dated to the MIS-2 (24.5 ± 2.8–21.2 ± 2.0 ka); the SGS-3 is speculatively ascribed to the Younger Dryas (YD) and the SGS-4 is suggested to be of the mid-Holocene (~6 ka) age. The bifurcated moraine ridges of SGS-2 represent standstill conditions during the post-Last Glacial Maximum (LGM) period. The deglaciation is represented by outwash gravel terraces, impounded sedimentary (lacustrine) sequences and fluvial drapes overlying and abutting the moraines are dated to early-mid (11.9 ± 0.9–7.5 ± 0.6 ka) and late Holocene (3.3 ± 0.2–1.7 ± 0.3 ka) intensified/moderate Indian Summer Monsoon. Considering the timing of glacial advances and stand-still condition, it is proposed that across the orographic barrier (rain shadow valleys), glaciers responded sensitively to the intensified anticyclonic flow of the cooler Mid-latitude Westerlies; implying that in a monsoon dominated transient climatic zone, even the rain shadow valleys responded sensitively to temperature changes.

High-frequency Holocene glacier fluctuations in the Himalayan-Tibetan orogen

Holocene glacial chronostratigraphies in glaciated valleys spread throughout the Himalayan-Tibetan orogen, including the Himalaya, Tibet, Pamir, and Tian Shan, are developed using a landsystems approach, detailed geomorphic mapping, and new and published 10Be surface exposure dating. New studies in the Kulti valley of Lahul and the Parkachik valley of the Nun Kun massif of the Himalaya of northern India define three glacier advances at ∼14.7, 12.2, 0.5 ka, in addition to one historically dated late 19th Century advance in the Kulti valley, and one Late Holocene advance at ∼0.2 ka in the Parkachik valley. Three major climatic groups (subdivided into five climatic zones) are defined across the orogen using Cluster Analysis (CA) and Principal Component Analysis (PCA) to identify glaciated regions with comparable climatic characteristics to evaluate the timing, and extent of Holocene glacier advances across these regions. Our regional analyses across the Himalayan-Tibetan orogen suggest at least one Lateglacial (∼15.3–11.8 ka) and five Himalayan-Tibetan Holocene glacial stages (HTHS) at ∼11.5–9.5, ∼8.8–7.7, ∼7.0–3.2, ∼2.3–1.0, and <1 ka. The extent (amplitude) of glacier advances in 77 glaciated valleys is reconstructed and defined using equilibrium-line altitudes (ELAs). Modern glacier hypsometries are also assessed to help explain the intra-regional variations in glacier amplitudes during each regional glacier advance. A linear inverse glacier flow model is used to decipher the net changes in temperature (ΔT) between periods of reconstructed regional glacier advances in 66 glaciated valleys across different climatic regions throughout the orogen. The 10Be, ELAs, and ΔT data suggest enhanced monsoonal and increased precipitation during the Early Holocene, followed by relative cooling and increased aridity during the Mid- and Late Holocene that influenced glaciation. The sublimation-dominated cold-based glaciers in the northern regions of Himalayan-Tibetan orogen are more affected during these shifts in climate than the temperate glaciers in the south.

Holocene glacier fluctuations in Patagonia are modulated by summer insolation intensity and paced by Southern Annular Mode-like variability

Alpine glaciers are sensitive indicators of changes in climate, and their ubiquity in mountainous regions make them valuable proxies for terrestrial climate reconstructions worldwide. However, the timing and extent of glacier change across the South American mid-latitudes through the Holocene are still poorly constrained relative to their counterparts in the Northern Hemisphere. Here we report a new 10Be surface exposure-based chronology of moraines recording a series of progressively less-extensive glacier advances of Glaciar Torre (Argentina, 49.3°S/73.0°W) since the Last Glacial Maximum, with expansions culminating at 17,600 ± 900, 13,500 ± 500, 9700 ± 400, 6900 ± 200, 6100 ± 300, 4500 ± 200, and 530 ± 60 yr BP. The declining magnitude of Holocene glacier expansions parallels a gradual rise in local summer insolation intensity during the Holocene, while individual advances occurred during inferred negative Southern Annular Mode (SAM)-like states at centennial to millennial timescales. These observations suggest that (i) summer insolation intensity modulated antiphased trends in glacier extent in the polar hemispheres during the Holocene, and that (ii) centennial-scale ‘SAM-like’ temperature and precipitation anomalies paced glacier fluctuations throughout Patagonia. Given the persistence of the inferred ’SAM-like’ anomalies throughout the Holocene, the modern measured trend towards positive SAM index conditions could mark the onset of a fundamental shift in the climate of the Southern Hemisphere midlatitudes that warrants consideration in projections of future climate.

New chronological constraints on the timing of Late Pleistocene glacier advances in northern Switzerland

Abstract. Deposits of the Reuss Glacier in the central northern Alpine foreland of Switzerland are dated using luminescence methodology. Methodological considerations on partial bleaching and fading correction of different signals imply the robustness of the results. An age of ca. 25 ka for sediment directly overlying basal lodgement till corresponds well with existing age constraints for the last maximal position of glaciers of the northern Swiss Alpine Foreland. Luminescence ages imply an earlier advance of Reuss Glacier into the lowlands during Marine Isotope Stage 4. The presented data are compared to findings from other parts of the Alps regarding glacier dynamics and palaeoclimatological implications, such as the source of precipitation during the Late Pleistocene.

Long-term records of glacier surface velocities in the Ötztal Alps (Austria)

Abstract. Climatic forcing affects glacier mass balance, which causes changes in ice flow dynamics and glacier length changes on different timescales. Mass balance and length changes are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics have been recorded. Here we present a unique dataset of yearly averaged ice flow velocity measurements at stakes and stone lines covering more than 100 years on Hintereisferner and more than 50 years on Kesselwandferner. Moreover, the dataset contains sub-seasonal variations in ice flow from Gepatschferner and Taschachferner covering almost 10 years. The ice flow velocities on Hintereisferner and (especially) on Kesselwandferner show great variation between advancing and retreating periods, with magnitudes increasing from the stakes at higher elevations to the lower-elevated stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong indicator of the negative mass balances of the glaciers in recent decades. The velocity datasets of the four glaciers are available at https://doi.org/10.1594/PANGAEA.896741.

Timing and Potential Causes of 19th-Century Glacier Advances in Coastal Alaska Based on Tree-Ring Dating and Historical Accounts

The Little Ice Age (LIA), ca. CE 1250-1850, was a cold period of global extent, with the nature and timing of reduced temperatures varying by region. The Gulf of Alaska (GOA) is a key location to study the climatic drivers of glacier fluctuations during the LIA because dendrochronologogical techniques can provide precise ages of ice advances and retreats. Here, we use dendrochronology to date the most recent advance of La Perouse Glacier in the Fairweather Range of Southeast Alaska. After maintaining a relatively contracted state since at least CE 1200, La Perouse advanced to its maximum LIA position between CE 1850 and 1895. Like many other glaciers bordering the GOA, the La Perouse Glacier reached this maximum position relatively late in the LIA compared with glaciers in other regions. This is curious because reconstructions of paleoclimate in the GOA region indicate the 19th century was not the coldest period of the LIA. Using newly available paleoclimate data, we hypothesize that a combination of moderately cool summers accompanying the Dalton Solar Minimum and exceptionally snowy winters associated with a strengthened Aleutian Low could have caused these relatively late LIA advances. Such a scenario implies that winter climate processes, which are heavily influenced by ocean-atmospheric variability in the North Pacific region, have modulated these coastal glaciers’ sensitivity to shifts in summer temperatures.