ABSTRACT Glaciers serve as sensitive indicators of climate change, with their dynamics significantly impacting regional water resources and global sea level rise. This study investigates the spatiotemporal evolution of glacier snow line altitude (SLA) and flow velocity in the Qilian Mountains during the early 21st century using remote sensing data. Results indicate a rising trend in SLA across both the western and central Qilian Mountains, with the central region exhibiting a higher rate of increase (11.2 m yr−1) compared to the western region (5.99 m yr−1). Concurrently, glacier flow velocities decelerated in both regions at similar rates (0.04 m yr−1 and 0.03 m yr−1, respectively). Glacier thinning observed since 2000, coupled with rising SLAs and decreasing velocities, collectively reflect a negative mass balance. Regional climate analysis reveals pronounced temperature increases (0.26–0.45°C per decade) and modest precipitation gains, aligning spatially with glacier retreat patterns. Overall, the observed changes in glacier behavior reflect the strong influence of ongoing climate change in the Qilian Mountain region.

The legacy of Pleistocene glaciation in the Babia Góra massif (1725 m a.s.l.) has been the subject of vigorous debate for over a century. These controversies have been largely influenced by the poor preservation of glacial landforms and their extensive overprint by rock slope failures (RSFs). In this context, geomorphological criteria alone have proven insufficient for a comprehensive interpretation of glacial features in flysch lithology, which has been heavily shaped by landslides. In this study, we present the results of field and LiDAR-supported geomorphological mapping, clast morphology analysis and micromorphological examination of sand-sized quartz grains. This multiproxy approach, when combined with previously published Schmidt-hammer data, provides robust evidence for the presence of glaciation in the Babia Góra massif. The Late Pleistocene palaeoglacier (area 0.87 km2, 2.2 km long) was reconstructed in the headwaters of the Szumiąca Woda valley. Mapped latero-frontal moraines mark the extent of the glacier front at 930 m a.s.l. The glacier equilibrium line altitude (ELA) calculated from glacier hypsometry with the area altitude balance ratio (AABR) 1.6 was 1272 m. However, after accounting for the topographic effect of additional snow accumulation, the climatic ELA was recalculated and placed at 1354 m a.s.l. These findings suggest that, in addition to the previously known eastward horizontal gradient of ELA rise, a southward trend of rising ELA was also observed across the Western Carpathians.

Aperture-averaged Polarimetry of the Second Interstellar Comet 3I/ATLAS within the Snow Line

Abstract Rockfalls are an efficient agent of landscape denudation and a crucial but poorly quantified component of the glacier debris supply cascade. Climate change is driving increased rockfall generation as rising air temperatures cause glacier thinning and thawing of permafrost. These processes alter rock slope stress profiles and thermal regimes, leading to greater sediment fluxes in cryospheric systems as landscapes adjust to ice‐free conditions. We used repeat terrestrial laser scans combined with change detection during the summer of 2019 to quantify rockfall activity over a 0.7 km 2 rock wall area along the ablation zone lateral margins of the debris‐covered Miage Glacier, Italy. We detected 2,581 rockfalls spanning eight orders of magnitude (10 −3 –10 4 m 3 ; median 0.021 m 3 ) including an event of about 28 × 10 3 m 3 from a newly deglaciated slope. Large rockfalls (≥10 m 3 ) on lower, glacier‐proximal slopes, whilst infrequent (<1% by count), achieved the most geomorphic work. Most (79%) rockfalls originated within <75 m above the glacier surface (mAG; representing 29% of the survey area); a boundary that corresponds with the Little Ice Age trimline. Some rockwalls exhibited a secondary zone of higher rockfall activity at about 125–150 mAG, revealing a second trimline with a millennial‐scale signal of elevated rock damage possibly associated with ice surface dynamics during or immediately after the Younger Dryas Stadial. Modelled rockfall runout distances were determined in part by path topography: rockfalls originating from lower slopes travelled <100 m horizontally whilst those originating higher could travel up to 650 m, approaching the glacier centreline, reflecting a spatial differential in hillslope‐glacier connectivity that will evolve concurrently with cryospheric degradation in the wider catchment. We show that detailed, short‐term monitoring campaigns can yield novel and useful descriptions of mass movement fluxes and spatial patterns in alpine regions. Expanding our dataset by observing rock walls near the equilibrium line altitude could help bridge the longitudinal gap to existing high elevation inventories to provide a more unified picture of rockfall dynamics in deglaciating catchments.

Water is one of the central molecules for the formation and habitability of planets. In particular, the region where water freezes out, the water snow line, could be a favorable location for planets to form in protoplanetary disks. We aimed to spatially resolve the water emission in the HL Tau disk using high-resolution ALMA observations of the H2O 183 GHz line (E_u = 205 K). We compared the spatially resolved H2O emission with that of H^13CO+ a chemical tracer of the water snow line, to observationally test their anticorrelation. In addition, we aimed to quantify the fraction of the water reservoir hidden by optically thick dust at ALMA wavelengths versus far- and mid-IR wavelengths. We used high-resolution ALMA observations to spatially resolve the H2O $ line at 183 GHz H^13CO+ J=2-1, and the SO $4_4-3_3$ transition in the HL Tau disk. A rotational diagram analysis was used to characterize the water reservoir seen with ALMA and compare it to the reservoir visible at mid- and far-IR wavelengths. We find that the H2O 183 GHz line has a compact central component and a diffuse component that is seen out to ∼ 75 au. A radially resolved rotational diagram shows that the excitation temperature of the water is ∼ 350 K, independent of radius. The steep drop in the water brightness temperature outside the central beam of the observations where the emission is optically thick is consistent with the water snow line being located inside the central beam (łesssim 6 au) at the height probed by the observations. Comparing the ALMA lines to those seen at shorter wavelengths shows that only $0.02%$ to $2%$ of the water reservoir is visible at mid- and far-IR wavelengths due to optically thick dust hiding the emission, whereas 35 to 70% is visible with ALMA. An anticorrelation between the H2O and H^13CO+ emission is found, but it is likely caused by optically thick dust hiding the H^13CO+ emission in the disk center. Finally, we see SO emission tracing the disk and, for the first time in SO, a molecular outflow and the infalling streamer out to ∼ 2". The velocity structure hints at a possible connection between the SO and the H2O emission. Spatially resolved observations of H2O lines at (sub)millimeter wavelengths provide valuable constraints on the location of the water snow line while probing the bulk of the gas-phase reservoirs.

Abstract. Glaciers are crucial indicators of climate change, and reconstructing their past geometries helps to understand past climate fluctuations. Various methods exist for reconstructing past glaciers, including simple power-law scaling and advanced GIS-based techniques that incorporate glacier outlines or surface hypsometry. However, these methods have limitations, such as not explicitly accounting for the physics of ice flow or mass conservation. Numerical glacier models, such as the Instructed Glacier Model (IGM), can overcome these limitations by incorporating ice-flow dynamics and mass conservation. This study presents the first Alps-wide, three-dimensional, model-derived reconstruction of glacier surfaces during the Little Ice Age in the European Alps, a period crucial for understanding pre-industrial natural climate variability. We simulate glaciers to match the empirically mapped Little Ice Age maximum extent at a resolution of 50 m. The simulation of the geometry of all glaciers of the European Alps resulted in a total ice volume of 283±42 km3. The reconstruction reveals regional and local patterns of equilibrium line altitudes derived separately for each glacier. These spatial patterns are influenced by factors such as air temperature, precipitation and shortwave radiation, highlighting the complex interplay of climatic and topographic factors in reconstructing these glaciers and their mass fluxes. A sensitivity analysis indicates an uncertainty of up to 14 % in the total ice volume and minimal sensitivity to parameter modifications for the equilibrium line altitude. Future work could include more sophisticated surface mass balance implementations to better understand the equilibrium line altitude patterns.

ABSTRACT Observations of interstellar comet 3I/ATLAS at 3.8 au show an elongated coma similar to a cometary tail but pointing in the direction of the Sun, possibly the first instance of this type of antitail which is not a result of perspective. We explain the antitail as an anisotropic extension of the snow line, or survival radius of a sublimating ice grain, in the direction of the Sun. The anisotropy is due to the difference in the sublimation mass flux in the solar and perpendicular directions caused by the change in the illumination angle of the cometary surface. The stronger sublimation mass flux in the solar direction results in ice grains with larger sizes, longer sublimation lifetimes, and a snow line at a larger radial distance with respect to other directions. The observed radial surface brightness profiles as a function of illumination angle are well reproduced by a Haser-type radial outflow with constant velocity and sublimating ice grains with angularly dependent survival lengths.

Abstract. Ice aprons are very small (generally < 0.1 km2) and thin (generally < 10 m) perennial ice bodies located on steep slopes with a quasi-stationary shear regime, frozen to steep permafrost rock slopes. They occupy – mainly above the glacier equilibrium line altitude – a very small fraction of the ice-covered surface but, with their quasi-stationary shear regime, contain ice that is multi-centennial to multi-millennial in age, making them a potentially important glacial heritage. In order to study these ice masses in their full thickness, a lightweight 10 m long ice corer was specially developed and successfully deployed on the northern face of Grandes Jorasses (4208 m a.s.l.) in July 2023. This article describes the technical characteristics of the ice corer and how it was used on a large ice apron of one of the largest rock faces in the Alps. It also presents the strategies we intend to use to analyse the extracted 8.8 and 6.0 m long ice cores.

Abstract Interstellar dust grains are enveloped by ices of frozen molecules in cold, dense regions of the interstellar medium (ISM), which are also observed in the gas phase. Whether a species is in the solid or gaseous state is governed by its binding energy (BE) on the grains. Hence, BEs are crucial in the solid-to-gas transition and are key input parameters for astrochemical models that simulate the physicochemical processes leading to the evolution of chemistry in the ISM. About 40% of the currently detected interstellar molecules belong to the category of interstellar complex organic molecules (iCOMs). This work aims to accurately evaluate the BEs of 19 iCOMs by means of quantum chemical calculations. Atomistic surface models simulating the structures of both crystalline and amorphous water ice were employed adopting a periodic approach, thereby accounting for the hydrogen bond (H-bond) cooperativity imparted by the extensive network present in the surfaces. A cost-effective but reliable procedure based on density functional theory was used to predict the structures of the adsorption complexes and calculate their BEs, which are mainly driven by H-bond and dispersion interactions, the latter presenting a fair contribution. A final discussion on the astrophysical implications of the computed BEs and the importance of obtaining reliable BEs on realistic interstellar ice surfaces in relation to the snow lines of iCOMs in hot cores/corinos and protoplanetary disks is provided.

Context . Rotational H 2 O spectra as observed with JWST/MIRI trace a wide range of excitation conditions and, thereby, provide a good probe of the temperature and column density structure of the inner disk. H 2 O emission can also be influenced by dynamical processes in the disk. In particular, dust grains can drift inward and their icy mantles sublimate once they cross the snow lines, thus enriching the inner regions in, for instance, H 2 O vapor. Recent work has found that this process may leave an imprint in the H 2 O spectrum in the form of excess flux in the cold, low- E up H 2 O lines. Aims . To interpret JWST spectra, local thermodynamic equilibrium (LTE) slab models are commonly used to determine the temperature, column density, and emitting region that is traced by the observed emission. In this work, we aim to test the accuracy of several common retrieval techniques on full 2D thermochemical disk models, to derive the underlying 2D distribution. Moreover, we investigate the cold H 2 O emission that has been proposed as a signature of drift, to gain further insights into the underlying radial and vertical distribution of H 2 O. Methods . We present two sets of Dust And LInes (DALI) thermochemical models, one in which the abundances are set by the chemical network, and the other in which the abundances are parameterized. We ran several commonly used retrieval techniques on the generated synthetic spectra and investigated how the retrieved temperature and column density compare to our models. Results . Single-temperature slab retrievals mainly trace the warm (~500 K) H 2 O reservoir, whereas a three-component fit is able to better trace the full temperature gradient in the IR emitting region. Retrieved temperatures tend to underestimate the true temperature of the emitting layer due to non-LTE effects such as sub-thermal excitation. The retrieved column density traces close to the mid-IR dust τ = 1 surface. We arrive at the same conclusion when performing this analysis for CO 2 emission and find that 13 CO 2 emission retrieves a lower temperature than 12 CO 2 due to it tracing deeper into the disk. Additionally, we find that our fiducial parameterized model predicts a very strong flux in the cold H 2 O lines, but only when the H 2 O abundance in the upper layers is high. The fiducial model with the full chemistry, by contrast, does not. Conclusions . We find that the strength of the cold H 2 O emission is directly linked to the H 2 O abundance above the snow surface at large radii (>1 au). This implies that sources in which the excess cold H 2 O flux is detected likely have a high H 2 O abundance in this region (≳10 −5 ) – higher than what is predicted by the chemical network. This discrepancy is most likely caused by the absence of dust transport processes in our models, further strengthening the theory that this emission may be a signature of radial drift and vertical mixing.

Abstract Exoplanet observations show that close-in super-Earths are more common around M-dwarfs than around solar mass stars. Since the snow line in a protoplanetary disc plays a crucial role in determining the amount of solid material available for planet formation, we explore the icy regions of protoplanetary discs around stars with masses 0.1, 0.5 and $1\rm \, M_\odot$. In a protoplanetary disc, a dead zone, where the magneto-rotational instability (MRI) is suppressed, provides a quiescent region for solids to settle to the mid-plane and planets to form. Viscosity may be driven in the dead zone by gravitational instability if enough material builds up. Heating from the gravitational instability can trigger the MRI and an accretion outburst onto the star. There may be two icy regions in a disc: (1) far from the star and (2) in the dead zone close to the star. We solve the 1D disc equations to find steady state solutions and time-dependent evolution with different values for the critical surface density in the MRI-active surface layers. Larger surface density in the MRI-active surface layers reduces the extent and lifetime of the inner icy region. The inner icy region in the dead zone around a solar mass star is small and short-lived. Around M-dwarfs, the size of the inner icy region is more persistent and oscillates between the accretion outbursts in the region $0.1-1\, \rm au$. An extended icy region within the dead zone of a disc around M-dwarfs may promote the formation of more numerous and massive close-in super-Earths.

Understanding of Southern Hemisphere glacier response to climatic changes is limited by a paucity of direct observations. However, glacier Equilibrium Line Altitudes (ELAs), which are determined by air temperature and precipitation and represent glacier mass balance, can be approximated using remote sensing of end of summer snowline altitudes (SLAEOS). This study shows that SLAEOS increased on the majority of 6364 glaciers and by up to 7.18 m yr−1 between 2000 and 2023 across five Southern Hemisphere mountain regions. Over this period anomalies from the multi-decadal mean SLAEOS became predominantly positive for all regions. In the most extreme cases, the rate of SLAEOS rise accelerated by up to x 4.0 in the western Southern Alps of New Zealand when comparing pre- and post-2010 rates of change. Contrastingly, the western Antarctic Peninsula and the western Southern Andes experienced declining SLAEOS and slowing rates of change at -1.0 and − 8.1 m yr−1, respectively. These spatio-temporal patterns reveal the interplay of temperature and precipitation, and the effects of them on a wide variety of mountain glaciers and ice cap outlet glaciers, with implications for understanding glacier response times, committed ice losses and overall meltwater production in the coming decades.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-19486-6.

Abstract In mountainous regions, a precise estimation of the snow cover area is crucial for a wide range of applications (hydrology, climatology, etc.). We present a new approach for estimating the total snow cover area in the French Alps using Sentinel-1 data, which are basically only used to detect the presence of wet snow. Wet snow monitoring is of interest for many applications, including hydrology and risk assessment. Our method involves calculating the likelihood of wet snow using Sentinel-1 images and a digital elevation model to obtain an estimate of the probability of wet snow for elevation and orientation classes. By identifying the snow lines (the elevation at which the snow is present homogeneously) and the transition from wet snow to dry snow, we can infer the classes associated with dry snow and thus, get an estimation of the total snow cover. Time series of wet and total snow cover are reconstructed over a decade (2015–2024). Estimates of total snow cover are compared with snow cover area from MODIS and Sentinel-2. We study the inter-annual, seasonal and spatial variability of wet and total snow over two massifs in the French Alps. Crocus snow model is used to infer the elevation of snow lines from snow depth simulations and to infer wet snow presence from the liquid water content, which are compared to snow cover derived from Sentinel-1. We show that monitoring (total/dry/wet) snow cover elevation at the massif scale provides useful information to study snow cover variability.

Current models of binary systems often depend on simplified approximations of the radiation field, which are unlikely to accurately capture the complexities of asymmetric environments. We investigate the dynamical and chemical implications of a 3D asymmetric radiation field that accounts for the optical properties of sub-structures present in a protoplanetary disk, as well as the inclusion of a secondary radiation source in binary systems. We conducted a series of 3D-SPH hydrodynamical simulations using Phantom coupled with the 3D Monte Carlo radiative transfer code Mcfost to compute disc temperatures on-the-fly . We explored different binary-disk orientations ($0 and $30 for an eccentric binary, along with a constant dust-to-gas ratio and dust as a mixture prescription. We also simulated an outburst event as an example of a drastic increase in luminosity. Heating from the secondary star inflates the outer disk, increasing the aspect ratio facing the companion by about 25% in inclined configurations compared to 10% in coplanar ones. Dust settling in the mid-plane enhances extinction along the disk plane, making the coplanar configuration cooler than the inclined one on the side of the disk facing the companion. Additional heating causes a shift in the snow line for species with freeze-out temperatures below 50 K, depending on the disk-binary inclination and binary phase. During outbursts, the aspect ratio doubles on the star-facing side and increases by 50% on the opposite side in inclined cases. The snow line shift would impact all the species considered in the outburst case. Protoplanetary disk heating in binary systems depends on stellar properties, the binary phase, and disk local and global characteristics. This results in temperature asymmetries, especially during secondary star outbursts, leading to variations in aspect ratio and snow lines that can affect chemistry and planet formation.

Abstract. We present new chronological and palaeoclimatological constraints on the evolution of the Valsugana glacier network (south-eastern European Alps) during the Last Glacial Maximum (LGM). The detection of ice-marginal sediments and landforms, related to the geological mapping of the area at 1 : 50 000 scale (CARG project, sheet 061 “Borgo Valsugana”), enabled a detailed reconstruction of past glaciers at their maximum extent. Chronological control on the geomorphological evidence is obtained using 10Be surface exposure dating of erratic boulders from lateral moraine ridges at Monte Lefre, a nunatak within the LGM ice network. The exposure ages cluster between 20 and 19 ka, demonstrating that lateral moraines were formed at the very end of the LGM and that ice surface lowering in the area did not start prior to ca. 19 ka. Isolated from the Valsugana glacier network, several smaller ice masses developed. The reconstruction of four of these isolated glaciers and their equilibrium line altitudes (ELAs) allows us to better understand the climatic conditions that controlled glacier evolution during the LGM: glacier ELAs were lowest in the Venetian Prealps (ca. 1300–1500 m a.s.l.) and were gradually rising towards the more internal mountain chains (ca. 1500–1700 m a.s.l.). This ELA gradient suggests that precipitation sourced from the Mediterranean Sea was highest in the vicinity of the Alpine fringe, with successive moisture starvation towards the north. The detailed glacier reconstructions, the chronological data, and the palaeoclimatological insights may serve as ground control for future modelling efforts of large and interconnected palaeoglacier networks.

Abstract Glacier mass balance is a key indicator of climate change, with most glaciers worldwide exhibiting negative trends due to rising temperatures. However, Adishi Glacier in the Central Caucasus presents an anomaly published by earlier studies. This research uses Ice, Clouds and Land Elevation Satellite‐2 altimetry data (2018–2024) and the Shuttle Radar Topography Mission Digital Elevation Model to assess recent elevation changes and mass balance variations. ERA5 reanalysis data were used to examine potential climatic drivers. Results show persistent thinning in lower glacier regions, while the accumulation area demonstrates sustained elevation gains. The equilibrium line altitude shows a slight upward trend (+3.07 m/year), consistent with global patterns. Notably, Adishi Glacier exhibited a positive mass balance of 0.05 ± 0.17 m w.e. a−1 in 2021 and 0.03 ± 0.06 m w.e. a−1 in 2024, but the mean for 2018–2024 remains negative at −0.31 ± 0.09 m w.e. a−1. This suggests that, despite short‐term gains, the anomaly is not sustained. Compared to the neighbouring glaciers—Bezengi, Khalde, Tsaneri North and South—which show continuous negative mass balances, Adishi's stability stands out. Regional warming (+0.19°C/year) based on ERA5 reanalysis contributes to ablation zone losses, but glacier hypsometry, with an extensive accumulation area above 4,000 m a.s.l., and orographic effect of snowfall on windward slopes support temporary gains. These favourable conditions, however, are insufficient to maintain a long‐term positive mass balance under ongoing climate change.

Abstract Tropical glaciers are rapidly retreating under anthropogenic global warming, posing significant hydrological, ecological, and socio‐environmental risks. In this commentary, I show that the freezing level height (FLH) is a robust, yet underutilized, indicator of glacier regime change in the tropical Andes. Building on recent work by Turner et al. (2025, https://doi.org/10.1029/2024jd042963), I argue that the strong association between FLH and glaciers' equilibrium line altitude (ELA) offers a simplified and simultaneously physically meaningful tool to anticipate glacier responses to atmospheric warming. Turner et al. (2025, https://doi.org/10.1029/2024jd042963) used FLH data from reanalysis and Coupled Model Intercomparison Project version model output to project 21st century ELA trajectories under two shared socioeconomic pathways (SSP2‐4.5 and SSP5‐8.5), predicting a nearly unabated rise in the ELA across studied regions, regardless of the emission scenario. While some observational constraints remain, the findings are applicable to most existing tropical glacier regimes. Importantly, rising FLH reflects a transition from humidity‐ to temperature‐driven mass balance, activating a cascade of positive feedbacks that accelerate ice loss. By reformulating an energy balance equation to express snowfall as a compensatory term, I demonstrate how the FLH can help identify resilient glacier landscapes, thereby informing conservation and adaptation priorities.

ABSTRACT Using highly irregular agglomerated debris particles, we analyse the polarimetric observations of the second interstellar Comet 3I/ATLAS beyond the snow line. Unlike the vast majority of Solar system comets at shorter heliocentric distance, modelling of the polarization of the inner coma in Comet 3I/ATLAS necessarily requires water-ice particles (30–40 per cent by volume). Our modelling suggests the other two species to be Mg-rich silicate and organics/amorphous carbon, which are common for Solar system comets. The relative abundance of the Mg-rich silicates is lower than what was needed in modelling the polarization of Solar system comets. The modelling suggests that if Comet 3I/ATLAS were to keep its activity at heliocentric distances smaller than that of the snow line, it would be an extremely high Pmax comet with Pmax ≈ 36–40 per cent in red light.

Abstract The influx of icy pebbles to the inner regions of protoplanetary disks constitutes a fundamental ingredient in most planet formation theories. The observational determination of the magnitude of this pebble flux and its dependence on disk substructure (disk gaps as pebble traps) would be a significant step forward. In this work, we analyze a sample of 21 T Tauri disks (with ages ≈0.5–2 Myr) using JWST/MIRI spectra homogeneously reduced with the JDISCS pipeline and high-angular-resolution Atacama Large Millimeter/submillimeter Array (ALMA) continuum data. We find that the 1500/6000 K water line flux ratio measured with JWST—a tracer of cold water vapor and pebble drift near the snow line—correlates with the radial location of the innermost dust gap in ALMA continuum observations (ranging from 8.7 to 69 au), confirming predictions from recent models that study connections between the inner and outer disk reservoirs. We develop a population synthesis exploration of pebble drift in gapped disks and find a good match to the observed trend for early and relatively effective gaps, while scenarios where pebble drift happens quickly, gaps are very leaky, or where gaps form late, are all disfavored on a population level. Inferred snow line pebble mass fluxes (ranging between 10−6 and 10−3 M ⊕ yr−1 depending on gap position) are comparable to fluxes used in pebble accretion studies and those proposed for the inner solar system, while system-to-system variations suggest differences in the emerging planetary system architectures and water budgets.

There is currently a debate about the timing and drivers of former glacier behaviour and climate change in the tropical Andes. Using 10Be dating we determined the ages of 21 boulders on moraines in the Santa Cruz Valley, Peru (∼10°S, altitudes ~ 4100 to ~ 4300m a.s.l.). Former glacier extent is marked by a suite of nested outer lateral and terminal moraines. These moraines are dated to 11.1ka, 11.6ka, 11.8ka and 12.0ka, falling within the Younger Dryas Chronozone (YDC; ∼12.9-11.6ka). Nine 10Be samples from the Lake Arhuaycocha catchment document a period of glacier thinning and lateral contraction between 12.0ka and 11.8ka. Reconstructed glacier Equilibrium Line Altitudes (ELA) at 11.0 to 12.0ka with an area-altitude balance ratio (AABR) of 1.00-2.50 are between 4675 and 4835m a.s.l. for the Arhuaycocha glacier, between 4692 and 4832m a.s.l. for the Taullicocha glacier and between 4800 and 4940m a.s.l. for the Artizon glacier. These values represent a depression of 300-400m in elevation compared to contemporary values for the ELA. We infer that the glacier advances at this time were driven by increased precipitation and that these changes were most likely a response to seasonal changes in the position of the ITCZ.