Glacier Extent Research Articles

Snow cover persistence reverses the altitudinal patterns of warming above and below 5000 m on the Tibetan Plateau

The Tibetan Plateau (TP) is a global warming hotspot, however, the warming status at high elevation (>5000 m) is poorly understood due to very sparse observations. Here we analyze spatial patterns in TP warming rates based on a novel near-surface air temperature dataset of 1980–2014 recently developed by ingesting high-elevation observations and downscaled reanalysis datasets. We show that the high snow cover persistence at high elevation reduces strengthening of positive feedbacks responsible for elevation dependent warming at low-middle elevations, leading to reversed altitudinal patterns of TP warming above and below 5000 m. An important negative feedback is induced by the presence of snow and glaciers at elevations above 5000 m, due to their “buffering” effects by consuming or reflecting energy that would be used for warming in the absence of snow or ice. A further decrease in snow cover and glacier extent at high elevations may thus amplify the warming on the TP.

The Role of Differential Ablation and Dynamic Detachment in Driving Accelerating Mass Loss From a Debris‐Covered Himalayan Glacier

AbstractSustained mass loss from Himalayan glaciers is causing supraglacial debris to expand and thicken, with the expectation that thicker debris will suppress ablation and extend glacier longevity. However, debris‐covered glaciers are losing mass at similar rates to clean‐ice glaciers in High Mountain Asia. This rapid mass loss is attributed to the combined effects of; (a) low or reversed mass balance gradients across debris‐covered glacier tongues, (b) differential ablation processes that locally enhance ablation within the debris‐covered section of the glacier, for example, at ice cliffs and supraglacial ponds, and (c) a decrease in ice flux from the accumulation area in response to climatic warming. Adding meter‐scale spatial variations in supraglacial debris thickness to an ice‐flow model of Khumbu Glacier, Nepal, increased mass loss by 47% relative to simulations assuming a continuous debris layer over a 31‐year period (1984–2015 CE) but overestimated the reduction in ice flux. Therefore, we investigated if simulating the effects of dynamic detachment of the upper active glacier from the debris‐covered tongue would give a better representation of glacier behavior, as suggested by observations of change in glacier dynamics and structure indicating that this process occurred during the last 100 years. Observed glacier change was reproduced more reliably in simulations of the active, rather than entire, glacier extent, indicating that Khumbu Glacier has passed a dynamic tipping point by dynamically detaching from the heavily debris‐covered tongue that contains 20% of the former ice volume.

The Holocene dynamics of Ryder Glacier and ice tongue in north Greenland

Abstract. The northern sector of the Greenland Ice Sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedish icebreaker Oden entered the previously unchartered waters of Sherard Osborn Fjord, where Ryder Glacier drains approximately 2 % of Greenland's ice sheet into the Lincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier and its ice tongue by combining radiocarbon dating with sedimentary facies analyses along a 45 km transect of marine sediment cores collected between the modern ice tongue margin and the mouth of the fjord. The results illustrate that Ryder Glacier retreated from a grounded position at the fjord mouth during the Early Holocene (> 10.7±0.4 ka cal BP) and receded more than 120 km to the end of Sherard Osborn Fjord by the Middle Holocene (6.3±0.3 ka cal BP), likely becoming completely land-based. A re-advance of Ryder Glacier occurred in the Late Holocene, becoming marine-based around 3.9±0.4 ka cal BP. An ice tongue, similar in extent to its current position was established in the Late Holocene (between 3.6±0.4 and 2.9±0.4 ka cal BP) and extended to its maximum historical position near the fjord mouth around 0.9±0.3 ka cal BP. Laminated, clast-poor sediments were deposited during the entire retreat and regrowth phases, suggesting the persistence of an ice tongue that only collapsed when the glacier retreated behind a prominent topographic high at the landward end of the fjord. Sherard Osborn Fjord narrows inland, is constrained by steep-sided cliffs, contains a number of bathymetric pinning points that also shield the modern ice tongue and grounding zone from warm Atlantic waters, and has a shallowing inland sub-ice topography. These features are conducive to glacier stability and can explain the persistence of Ryder's ice tongue while the glacier remained marine-based. However, the physiography of the fjord did not halt the dramatic retreat of Ryder Glacier under the relatively mild changes in climate forcing during the Holocene. Presently, Ryder Glacier is grounded more than 40 km seaward of its inferred position during the Middle Holocene, highlighting the potential for substantial retreat in response to ongoing climate change.

A decade of surface meteorology and radiation fluxes at Brewster Glacier in the Southern Alps of New Zealand

AbstractHigh‐altitude observations of mountain meteorology remain extremely rare in the Southern Alps despite their importance for detecting changes in seasonal snow and glacier extent. To address this, we present a unique in situ analysis of surface meteorology, including radiative forcing from clouds, using automatic weather station data obtained near the terminus of Brewster Glacier in the Southern Alps of New Zealand over the period 2010–2020. The average air temperature is 2.1°C at an altitude of 1,650 m above sea level, and seasonal cycles of surface temperature and albedo indicate the automatic weather station (AWS) site is typically snow‐covered between June and November. Snowfall can occur anytime of the year, but rainfall accounts for more than half of the total precipitation (56%). In the absence of strong gradient airflow, a katabatic wind often develops on the glacier, which is strongest at night time and early morning. Partly cloudy conditions are most frequent (43%) at a daily time scale, followed by overcast (34%) and clear‐sky conditions (23%). A distinct diurnal and seasonal cycle of cloud cover is observed, with clouds most frequent in the afternoon during spring. Daily clear‐sky conditions are most common during winter, in particular in June, while the atmospheric transmission of shortwave radiation is lowest in summer. For 4 months of the year (May–August), the increase in incoming longwave radiation by clouds exceeds the decrease in incoming shortwave radiation. Interannual extremes in melt on Brewster Glacier cannot be fully attributed to summer air temperature anomalies and future work should seek to examine the influence of clouds and atmospheric moisture fluxes on seasonal mass balance variations.

Late Quaternary glacial advances and equilibrium-line altitude changes in a semi-arid region, Suru Basin, western Himalaya

This study examines the late Quaternary glacial history of Suru Basin and its associated tributary valleys (i.e., Achambur, Kangriz, Shafat, Rangdum, and Pensilugnpa), western Himalaya, based on the data collected from field surveys (2015–2019), satellite images, and optically stimulated luminescence (OSL) dating. The glaciers in Suru Basin have fluctuated greatly throughout the Marine Isotope Stages (MIS) 3 and 2 to the Little Ice Age (LIA), and are critical in understanding the linkages between regional and global climate change. Here, we present a detailed record of five major glacial advances of decreasing magnitude, dated 33–23 ka, 16 ka, 13–11 ka, 10–7.3 ka, 2.8–2.3 ka, and a minor advance dated 0.7–0.4 ka. These five major glacial advances are named from oldest to youngest as Suru-I to V, based on their optical chronology, geographical position, moraine stratigraphy, and glacially polished rock surfaces. Whereas, the equilibrium-line altitude (ELA) ascended by ∼538 m from the oldest glacial advance (Suru-I) to the present-day, followed by four other events (Suru-II, III, IV, and V) with ascended ELAs of ∼522, ∼399, ∼243, and 215 m, respectively. Suru Basin has lost ∼502 km2 in its glaciated area and ∼163 km3 in ice volume from Suru-I to the present-day. The magnitude of glacier extent decreased from the MIS 3 and 2, early to late-Holocene, and LIA. The timing of these glacial advances is coarsely in agreement with North Atlantic millennial-scale climate oscillations (Heinrich events), signifying the probable correlation between these abrupt climate changes and glacial fluctuations in this semi-arid region of the Himalaya.

Local summer insolation and greenhouse gas forcing drove warming and glacier retreat in New Zealand during the Holocene

Geological climate archives from the Holocene Epoch provide baseline information concerning natural climate variability. Temperate mountain glacier extent is sensitive to summer air temperature, thus geological records of past glacier length changes are a useful proxy for this climatic variable. Here we present a new cosmogenic 10Be chronology of glacier length changes at Dart Glacier in the Southern Alps, New Zealand. Prominent moraines deposited 321 ± 44 yr ago (n = 11) and 7.8 ± 0.3 ka (n = 5) show glaciers during the Little Ice Age were less extensive than during the early Holocene. This pattern of net Holocene glacier retreat is consistent with emerging data from other catchments in New Zealand and across the southern mid-latitudes. Using the physical framework of a transient global climate model simulation, we suggest that cool summers in the early Holocene were promoted by the local summer insolation minimum, together with low atmospheric greenhouse gas concentrations, causing an early Holocene austral glacial maximum. An insolation-driven reduction in seasonality at southern mid-latitudes may reconcile differences between early Holocene temperature reconstructions where climate proxies have different seasonal sensitivities. We suggest that rising greenhouse gas concentrations after 7 ka caused regional-scale glacier retreat and appear to be the dominant driver of multi-millennial summer temperature trends in the southern mid-latitudes during the present interglacial.

High-Resolution Monitoring of Glacier Mass Balance and Dynamics with Unmanned Aerial Vehicles on the Ningchan No. 1 Glacier in the Qilian Mountains, China

Glaciers located in the Qilian Mountains are rapidly retreating and thinning due to climate change. The current understanding of small glacier mass balance changes under a changing climate is limited by the scarcity of in situ measurements in both time and space as well as the resolution of remote sensing products. Unmanned aerial vehicles (UAVs) provide an unparalleled opportunity to track the spatiotemporal variations in glacier extent at a high resolution and the changing glacier morphological features related to glacial dynamics. Five measurements were performed on the Ningchan No. 1 (NC01) glacier in the Qilian Mountains between 18 August 2017 and 13 August 2020. The glacier changes displayed in the digital orthophoto maps (DOMs) and digital surface models (DSMs) show a 7.4 ± 0.1 m a−1 retreat of the terminus of NC01, a mass balance of −1.22 ± 0.1 m w.e. a−1 from 2017 to 2020, and a maximum surface velocity of 3.2 ± 0.47 m from 18 August 2017 to 26 August 2018, which clearly show consistency with stake measurements. The surface elevation change was influenced by the combined effects of air temperature, altitude, slope, and surface velocity. This research demonstrates that UAV photogrammetry can greatly improve the temporal and spatial resolution of glaciological research.

Late Quaternary glacial history of the Altyn Tagh Range, northern Tibetan Plateau

Quantifying the timing and extent of late Quaternary glaciations across the Tibetan Plateau (TP) is critical to understanding regional and global climate changes. Despite significant advancements in our knowledge of glacial histories of the TP over the past several decades, chronological constraints are still lacking for the high glaciated mountain ranges on the northern TP, including the Altyn Tagh Range. In this study, we provide thirty-two new 10Be exposure-ages to construct a late Quaternary glacial history of the Altyn Tagh Range at the Altyn “Pass” and Akato Tagh. The dating results from Altyn “Pass” indicate that glacier might have fully melted out of this area after Marine Isotope Stage 3 (MIS 3). The tentatively-defined minimum moraine ages north of Akato Tagh show that four glacial culminations possibly occurred during MIS 5, MIS 4, MIS 3 or 2, and the late Holocene. These dating results, together with the compiled exposure-ages from Sulamu Tagh, imply that the last glacial glacier fluctuations along the Altyn Tagh Range were likely driven by several factors: North Atlantic climate oscillations, northern hemispheric high-latitude summer solar insolation, atmospheric CO2 concentrations, and geometry of glacier catchment. The progressive reduction in glacier extent during the last glacial is likely associated with available precipitation, controlled by the mid-latitude westerlies.

Divergent Evolution of Glaciation Across High‐Mountain Asia During the Last Four Glacial‐Interglacial Cycles

AbstractGlaciers over High‐Mountain Asia (HMA) provide a critical window into past climate change and the linkage between high and low‐latitude glaciation, but how glaciers may have varied during past glacial‐interglacial cycles remains elusive. Here, we reconstruct the timing and extent of glaciations for the last 425 kyr over HMA, using a climate‐glaciation simulation constrained by observations and glacial geologic evidence. We illustrate that there were multiple alpine‐style glaciations comparable in extent to those during the last glacial maximum during the last four glacial‐interglacial cycles. The extent and timing of glaciations vary across HMA, especially between the westerly influenced northern and the monsoonal‐influenced southern HMA. The ∼23‐kyr periodicity dominates HMA glaciation due to the critical role of precession in regulating summer temperature and precipitation. Our results, in addition to helping to fill the incomplete glacial geologic record, provide a framework to test hypotheses linking orbital‐scale climate, glaciation, and landscape evolution over HMA.

Penultimate Glacial Cycle glacier extent in the Iberian Peninsula: New evidence from the Serra da Estrela (Central System, Portugal)

The objective of this work is to present a first assessment on the age of the glacial features of the Serra da Estrela, in the central Portugal, Iberian Peninsula (40°19′ N, 7°37′ W, 1993 m), using Cosmic-Ray Exposure dating (in situ cosmogenic 36Cl). A total of 6 samples were dated, 4 extracted from exposed moraine boulders and 2 from glacially polished bedrock surfaces. Despite the low number of samples, the results are consistent, reinforcing previous dating obtained by other methods and geomorphological and paleoclimatic information. The maximum extension of the glaciers occurred at the end of the Penultimate Glacial Cycle (Marine Isotope Stage 6), during Heinrich Stadial 11, around 140 ka. At the end of the Last Glacial Cycle, slightly before the Last Glacial Maximum, at around 30 ka, the Estrela glaciers reached again a similar extent. Finally, the glaciers disappeared from the Serra da Estrela at the beginning of the Bølling-Allerød Interstadial, at around 14.2 ka. These data confirm a certain synchronicity in the major glacial phases in most the Mediterranean and also European mountains, although there are notable differences in the maximum extent in the two cycles.

Spatiotemporal changes of glacier and seasonal snow fluctuations over the Namcha Barwa–Gyala Peri massif using object-based classification from Landsat time series

The glacier environment in the Namcha Barwa–Gyala Peri (NBGP) massif is regarded as one of the most sensitive areas to climate change, yet the change estimates remain inadequate due to the limited knowledge of the complex debris-covered glacier environment and the lack of available remote sensing data caused by continuously cloudy weather. To examine the changes of the complex glacial environment, a multiple hierarchical object- and rule-based classification (MHORC) scheme is proposed by combining Landsat time series images and topographic data. Object-based image analysis (OBIA) is introduced due to its capabilities of handling data contextually and hierarchically and using multi-source data jointly so that multiple hierarchical rule-based classification can be developed to distinguish the objects with similar spectrum such as debris-covered glaciers and their surrounding terrain. All the available Landsat images from 1987 to 2019 are filtered by the cloud cover condition (less than 10%) and accordingly used in the MHORC to obtain spatial and temporal information of the glacier and snow over the NBGP massif. The images collected in the snow-free season are used to estimate the glacier extent state and the historical changes, and those in the snow-covered are used to estimate the snow cover fluctuation using harmonic analysis. The results show that the NBGP contains 65 glaciers (≥0.1 km2) with a total area of 462.7 km2, among which valley glaciers account for 21.5% in number but cover an area of 354.2 km2, more than 76% of the total area. An accelerating reduction trend of the glacier area is confirmed as the area change velocity is −0.62 km2 yr−1 between 1999 and 2003 and reach −2.95 km2 yr−1 between 2003 and 2015. The seasonal snow cover area shows a reduction in the secular trend and an increase in fluctuation amplitude. Both glacier and seasonal snow display heterogeneity in the spatial and temporal patterns. Such heterogeneous dynamics might be related to the trade-off between water vapor supply and regional thermal conditions. This MHORC developed in this study demonstrates its effectiveness in delineating the debris-covered glacier environment and the potential of using Landsat time series to track glacial environment evolution. Besides, the analysis of seasonal snow fluctuations provides a novel perspective to re-recognize the glacial environment dynamics, and the knowledge of glacier extent changes and season snow fluctuations over the NBGP massif can improve the understanding of environmental effects from climate change.

Modelling and characterizing glacier-bed overdeepenings as sites for potential future lakes in the deglaciating French Alps

Glacier retreat results in major landscape changes including the formation of new lakes in Glacier-Bed Overdeepenings (GBOs) that can provoke catastrophic Glacial Lake Outburst Flood (GLOF) hazards, but could also provide economic opportunities. This study aims to identify and characterize the location of potential GBOs in the French Alps as possible sites for future lakes. We first ran GlabTop (Glacier-bed Topography) and GlabTop2 models, two GIS schemes calculating glacier ice thickness and mapping potential GBOs. Their level of confidence is estimated using morphological analysis based on slope angle, crevasse fields and lateral narrowing at bedrock thresholds. 139 GBOs (>0.01km²) were predicted among which 59 have medium to very high confidence. 20 lakes are already forming at the snout of retreating glaciers, including four lakes at predicted GBOs <0,01km². The Vanoise massif hosts 43% of the predicted GBOs but the Mont Blanc massif gathers larger, deeper and more voluminous ones. Most of the predicted GBOs are below 3,500m a.s.l. as related to the elevation of the corresponding glaciers. In the Vanoise massif, many predicted GBOs have rather low confidence because of the extent of ice-cap like glaciers for which the shear stress approach used by GlabTop becomes questionable. Furthermore, 58 potential GBOs were detected by visual analysis of glacier morphologies. The study highlights the relevance of combining various methods to determine GBOs and is a first step towards the anticipation of future risks and opportunities related to the formation of new lakes in the French Alps.

Modeling the retreat of the Aneto Glacier (Spanish Pyrenees) since the Little Ice Age, and its accelerated shrinkage over recent decades

The Aneto, located on the Maladeta Massif (Central Pyrenees), is the largest glacier of the Pyrenees. The glacier is 675 m long, occupies an area of 48.64 ha and has a maximum altitude of 3269 m. In this study, we present a detailed area, volume, ice thickness, and Equilibrium Line Altitude reconstruction of the glacier for different periods (LIA, 1957, 1983, 2000, 2006, 2015, and 2017) and analyze its retreat. To estimate the glacier extent during the LIA, the moraines were mapped by using photo interpretation techniques whereas for the recent stages digital satellite images and aerial photographs were used. Moreover, we estimated the topography of the glacier using a simple steady-state model that assumes a perfectly plastic ice rheology, which allowed reconstructing the theoretical ice profiles of the glacier. To reconstruct the ice surface, a digital elevation model was created and combined with the bedrock topography in order to obtain the ice thickness of each stage. The results of the study reveal a considerable retreat of the Aneto Glacier since the LIA. The length of the glacier has reduced from 1970 to 675 m from LIA to2017, and its tongue has retreated from 2385 to 3029 m a.s.l. Furthermore, the glaciated area has been reduced from 245 to 48.64 ha from LIA to 2017 and the ELA has risen from 2919 to 3139 m a.s.l. The data obtained indicates that in the LIA–2017 period the glacier volume has been reduced from 82.57 m × 106 m3 to 3.48 m × 106 m3 and the maximum ice thickness from 95 to 27m. We also reconstructed the climatic conditions, showing an increase in temperature of ~1.14°C from LIA to 2017. These data reveal a vast retreat of the glacier since the LIA, which has accelerated since the 1980’s and even more since the year 2000.

Little Ice Age glacier extent and temporal changes in annual mass balance (2016–2019) of Pensilungpa Glacier, Zanskar Himalaya

Glaciers and climate are known to exhibit positive feedbacks that are important for comprehending the overall glacier state. This relation is poorly understood in the relatively unexplored terrain like the Zanskar Himalaya. We have studied the impact of climate change regarding the past and present response of the Pensilungpa Glacier (PG), Zanskar Himalaya. Reconstructing the recent changes in the mass balance (2016–2019) along with the Little Ice Age (LIA) extent of the PG shows that the PG was joined by the five tributary glaciers during the LIA having an area of ~ 18 km2 and extended ~ 3 km downstream from its present-day snout located at 4470 ± 1 m.a.s.l. Since the LIA, the PG has retreated ~ 2941 ± 75 m, at an average rate of 5.6 ± 0.15 m a−1. Field observations for the last 4 years (2015–2019) show that the glacier now is retreating by ~ 27 ± 11 m at an average rate of 6.7 ± 3 m a−1, which is similar to the one since the LIA. The glaciers in the study area (Suru River valley) are mostly nourished by the Western Disturbances (during the December, January, and February) with maximum solid precipitation, and melt during the ablation period (May–October). The observed recessional trends of the PG may, therefore, be attributed to an increase in the temperature and decrease in precipitation during accumulation period. The ablation data reveal the significant influence of debris-cover on the mass balance and terminus retreat of the PG. Furthermore, the mass balance data for the last 3 years (2016–2019) show a negative trend with a small accumulation area ratio (AAR) (43%). The average net annual mass balance is estimated to be ~ − 3.67 × 106 m3 w.e. a−1 with the − 0.36 m w.e. a−1 specific balance between 2016 and 2019. During the period 2016–2019, the PG has lost ~ 11.03 × 106 m3 w.e. ice volume. The slower retreat rate and low AAR of the PG, compared to other glaciers in the area, suggest that its terrain characteristics (hypsometry, size, aspect, and slope) control the glacier dynamics and the glacier continues to adjust geometrically in response to the negative mass balance.

Vegetation and Glacier Trends in the Area of the Maritime Alps Natural Park (Italy): MaxEnt Application to Predict Habitat Development

Climate change is significantly affecting ecosystem services and leading to strong impacts on the extent and distribution of glaciers and vegetation. In this context, species distribution models represent a suitable instrument for studying ecosystem development and response to climate warming. This study applies the maximum entropy model, MaxEnt, to evaluate trends and effects of climate change for three environmental indicators in the area of the Alpi Marittime Natural Park under the Municipality of Entracque (Italy). Specifically, this study focuses on the magnitude of the retreat of six glaciers and on the distribution of two different plant communities, Alnus viridis scrub and Fagus sylvatica forest associated with Acer pseudoplatanus and tall herbs (megaforbie), in relation to predicted increases in mean temperatures. MaxEnt software was used to model and observe changes over a thirty-year period, developing three scenarios: a present (2019), a past (1980) and a future (2050) using 24 “environmental layers”. This study showed the delicate climate balances of these six small glaciers that, in the next 30 years, are likely to undergo an important retreat (≈−33%) despite the high altitude and important snowfall that still characterize the area. At the same time, it is predicted that the two plant communities will invade those higher altitude territories that, not so long ago, were inhospitable, expanding their habitat by 50%. The MaxEnt application to glaciers has shown to be an effective tool that offers a new perspective in the climate change field as well as in biodiversity conservation planning.

Glacier retreat and associated processes since the Last Glacial Maximum in the Lejiamayu valley, Peruvian Andes

In this study, we examine glacier retreat and associated processes in the Lejiamayu valley, central Cordillera Blanca, Peru (9.27°S; 77.48°W) since the Last Glacial Maximum (LGM). Based on detailed mapping of well-preserved moraines, we reconstruct glacier extent during the LGM, the Antarctic Cold Reversal (ACR) and the Little Ice Age (LIA), being 21.34 km2 (LGM), 13.68 km2 (ACR) and 6.84 km2 (LIA). We document that glacier extent decreased to 2,86 km2 since the end of the LIA in this catchment (ice loss 58%). In addition, we explore the colonization and growth of lichens and Schmidt-hammer rock test R-values over the deglaciated surfaces, suggesting a relationship to possible evironmental controls rather than to the timing of the exposure. Further, we use empirical glacier velocity-based equation to estimate maximum potential future volume of the new glacial lake forming in the upper part of the valley (4725 m a.s.l.; 2.2 Mm3). We conclude that previous estimates of future lake volume might have been underestimated and that the sufficiency of the glacial lake outburst flood (GLOF) mitigation measures implemented at downstream located Lake Lejiacocha (4628 m a.s.l.) should be revised in future.

Timing and extent of Late Pleistocene glaciation in the Chugach Mountains, Alaska

AbstractGeomorphic mapping, landform and sediment analysis, and cosmogenic10Be and36Cl ages from erratics, moraine boulders, and glacially polished bedrock help define the timing of the Wisconsinan glaciations in the Chugach Mountains of south-central Alaska. The maximum extent of glaciation in the Chugach Mountains during the last glacial period (marine isotope stages [MIS] 5d through 2) occurred at ~50 ka during MIS 3. In the Williwaw Lakes valley and Thompson Pass areas of the Chugach Mountains, moraines date to ~26.7 ± 2.4, 25.4 ± 2.4, 18.8 ± 1.6, 19.3 ± 1.7, and 17.3 ± 1.5 ka, representing times of glacial retreat. These data suggest that glaciers retreated later in the Chugach Mountain than in other regions of Alaska. Reconstructed equilibrium-line altitude depressions range from 400 to 430 m for late Wisconsinan glacial advances in the Chugach Mountains, representing a possible temperature depression of 2.1–2.3°C. These reconstructed temperature depressions suggest that climate was warmer in this part of Alaska than in many other regions throughout Alaska and elsewhere in the world during the global last glacial maximum.

The Lowest Elevated Pleistocene Glaciers in the Carpathians – Geomorphological and Sedimentological Record of Glaciation in the Polonyna Rivna and Borzhava Massifs (Ukraine Carpathians)

The Polonyna Rivna (1480 m asl) and Borzhava (1682 m asl) ranges represent the medium-high mountain massifs located in the north-western part of the Ukrainian Carpathians, where the legacy of the Pleistocene glaciation has long been unexplored. Based on the first detailed mapping of glacial landforms and sedimentological analysis, we document the presence of freshly-shaped outer moraines and glacial cirques and reconstruct the extent and ice-surface geometry of the six very small (0.09–0.78 km2 area) palaeoglaciers. The specific feature of the area is the presence of extensive mountain-top plateaus that play an important role as additional areas for snowblow accumulation. The equilibrium line altitudes (ELAs) calculated from hypsometry of reconstructed maximal glacier extent using the area x altitude balance ratio (AABR) 1.6 method is exceptionally low at 1138 m in the Polonyna Rivna and 1230 m in the Borzhava range. Excluding the topographic effect produced by additional snow accumulation the ELA shift upwards between 120 – 180 m which corresponds to 25 – 53% of the glacier elevation range. The resulted climatic ELA (1282–1352 m) together with the mean cirque floor altitude (1194 m) and mean elevation of the glacier fronts (994 m asl) represent the lowest values in the entire Carpathian arc. Our data indicate glacier-friendly conditions in the mountain massifs exceeding 1400 m asl in the windward NW part of the Ukrainian Carpathians where due to relatively cold air temperatures and orographic induced precipitation local topolimatic factors dictated the development of marginal glaciation.

Glacier Cover Change Assessment of the Columbia Icefield in the Canadian Rocky Mountains, Canada (1985–2018)

Meltwater from glaciers makes significant contributions to general streamflow and provides water for flora and fauna. Continuous glacier monitoring programs enhance our understanding of the impacts of global warming on glaciers and their topographical features. The objective of this study is to measure spatial and temporal changes in Canada’s Columbia Icefield glaciers. This study uses Landsat (TM 5 and OLI) images to delineate glacier extents in the Columbia Icefield between 1985 and 2018. The study also analyzes the retreat of the Athabasca, Castleguard, Columbia, Dome, Saskatchewan, and Stutfield Glaciers. The total area covered by the Icefield in 1985 was 227 km2. By 2018, the Icefield had lost approximately 42 km2 of its area coverage, representing 18% of its previous coverage. All glaciers in the study region retreated and decreased in area over the study period. The pattern observed in this study is one of general ice loss in the Columbia Icefield, which mirrors patterns observed in other mountain glaciers in Western Canada.

A national glacier inventory and variations in glacier extent in Iceland from the Little Ice Age maximum to 2019

A national glacier outline inventory for several different times since the end of the Little Ice Age (LIA) in Iceland has been created with input from several research groups and institutions, and submitted to the GLIMS (Global Land Ice Measurements from Space, nsidc.org/glims) database, where it is openly available. The glacier outlines have been revised and updated for consistency and the most representative outline chosen. The maximum glacier extent during the LIA was not reached simultaneously in Iceland, but many glaciers started retreating from their outermost LIA moraines around 1890. The total area of glaciers in Iceland in 2019 was approximately 10,400 km², and has decreased by more than 2200 km² since the end of the 19th century (corresponding to an 18\% loss in area) and by approximately 750 km² since ∼2000. The larger ice caps have lost 10–30\% of their maximum LIA area, whereas intermediate-size glaciers have been reduced by up to 80\%. During the first two decades of the 21st century, the decrease rate has on average been approximately 40 km² a$^{−1}$. During this period, some tens of small glaciers have disappeared entirely. Temporal glacier inventories are important for climate change studies, for calibration of glacier models, for studies of glacier surges and glacier dynamics, and they are essential for better understanding of the state of glaciers. Although surges, volcanic eruptions and jökulhlaups influence the position of some glacier termini, glacier variations have been rather synchronous in Iceland, largely following climatic variations since the end of the 19th century.