Sensitivity Of Glaciers Research Articles

A scenario–neutral approach to climate change in glacier mass balance modeling

Abstract Scenario–neutral methods are commonly used to rapidly compare system responses to changes in climate. Using glacier mass balance as a system response, we present a bottom-up, scenario–neutral method as an effective tool for preliminary and overview studies on glacier sensitivity and a complementary approach to traditional top–down methods. The method's main characteristic is its visual result: two–dimensional response surfaces depicting glacier mass balance. Their axes represent perturbations in temperature and precipitation relative to a baseline. The simplicity of our approach makes it applicable to all global glaciers. As a proof–of–concept, the Open Global Glacier Model (OGGM) is used to perform a scenario–neutral glacier sensitivity analysis for four glaciers. In addition, the integration with a top–down approach is demonstrated by overlaying temperature and precipitation from four Coupled Model Intercomparison Project Phase 6 (CMIP6) models, under four Shared Socioeconomic Pathways (SSP). Finally, the benefits of the method are discussed for decision–making and science communication. Assessing results shows that overall, this scenario–neutral method can provide useful information for the research of climate change impact on glacier mass, from aiding study design to science communication.

A high-resolution calving front data product for marine-terminating glaciers in Svalbard

Abstract. The mass loss of glaciers outside the polar ice sheets has been accelerating during the past several decades and has been contributing to global sea-level rise. However, many of the mechanisms of this mass loss process are not well understood, especially the calving dynamics of marine-terminating glaciers, in part due to a lack of high-resolution calving front observations. Svalbard is an ideal site to study the climate sensitivity of glaciers as it is a region that has been undergoing amplified climate variability in both space and time compared to the global mean. Here we present a new high-resolution calving front dataset of 149 marine-terminating glaciers in Svalbard, comprising 124 919 glacier calving front positions during the period 1985–2023 (https://doi.org/10.5281/zenodo.10407266, Li et al., 2023). This dataset was generated using a novel automated deep-learning framework and multiple optical and SAR satellite images from Landsat, Terra-ASTER, Sentinel-2, and Sentinel-1 satellite missions. The overall calving front mapping uncertainty across Svalbard is 31 m. The newly derived calving front dataset agrees well with recent decadal calving front observations between 2000 and 2020 (Kochtitzky and Copland, 2022) and an annual calving front dataset between 2008 and 2022 (Moholdt et al., 2022). The calving fronts between our product and the latter deviate by 32 ± 65 m on average. The R2 of the glacier calving front change rates between these two products is 0.98, indicating an excellent match. Using this new calving front dataset, we identified widespread calving front retreats during the past four decades, across most regions in Svalbard except for a handful of glaciers draining the ice caps Vestfonna and Austfonna on Nordaustlandet. In addition, we identified complex patterns of glacier surging events overlaid with seasonal calving cycles. These data and findings provide insights into understanding glacier calving mechanisms and drivers. This new dataset can help improve estimates of glacier frontal ablation as a component of the integrated mass balance of marine-terminating glaciers.

Ubiquitous acceleration in Greenland Ice Sheet calving from 1985 to 2022.

Nearly every glacier in Greenland has thinned or retreated over the past few decades1-4, leading to glacier acceleration, increased rates of sea-level rise and climate impacts around the globe5-9. To understand how calving-front retreat has affected the ice-mass balance of Greenland, we combine 236,328 manually derived and AI-derived observations of glacier terminus positions collected from 1985 to 2022 and generate a 120-m-resolution mask defining the ice-sheet extent every month for nearly four decades. Here we show that, since 1985, the Greenland Ice Sheet (GrIS) has lost 5,091 ± 72 km2 of area, corresponding to 1,034 ± 120 Gt of ice lost to retreat. Our results indicate that, by neglecting calving-front retreat, current consensus estimates of ice-sheet mass balance4,9 have underestimated recent mass loss from Greenland by as much as 20%. The mass loss we report has had minimal direct impact on global sea level but is sufficient to affect ocean circulation and the distribution of heat energy around the globe10-12. On seasonal timescales, Greenland loses 193 ± 25 km2 (63 ± 6 Gt) of ice to retreat each year from a maximum extent in May to a minimum between September and October. We find that multidecadal retreat is highly correlated with the magnitude of seasonal advance and retreat of each glacier, meaning that terminus-position variability on seasonal timescales can serve as an indicator of glacier sensitivity to longer-term climate change.

Investigating the past, present and future responses of Shallap and Zongo Glaciers, Tropical Andes, to the El Niño Southern Oscillation

Abstract Tropical Andean glaciers are highly sensitive to climate change and are impacted by the El Niño Southern Oscillation (ENSO). However, glaciological data are scarce, meaning that there are substantial knowledge gaps in the response of Andean glaciers to future anthropogenic and ENSO forcing and these are crucial to address, as glaciers represent a key water source for downstream populations and ecosystems. Here we integrated data from glaciological field studies, remote sensing, statistical analysis and glacier modelling to analyse the response of two Andean glaciers (Zongo and Shallap) to ENSO and their potential sensitivity to a range of climate forcing scenarios. Both glaciers retreated and experienced increasingly negative mass balance between the 1990s and the 2010s and responded strongly and rapidly to contemporary ENSO forcing, although this relationship evolved over time. Sensitivity experiments demonstrate that Shallap and Zongo are highly sensitive to ENSO forcing scenarios and the combination of ENSO and climate warming can cause rapid ice loss under the most extreme scenarios. Results also demonstrate the strong sensitivity of both glaciers to changes in the equilibrium line altitude, whereby rapid ice loss occurred when melt extended into present-day accumulation areas.

Spatial pattern of glacier mass balance sensitivity to atmospheric forcing in High Mountain Asia

Abstract The complex topography and size of High Mountain Asia (HMA) result in large differences in glacier mass-balance variability and climate sensitivity. Current understanding of these sensitivities is limited by simplifications in past studies’ model structure. This study overcomes this limitation by using a mass-balance model to investigate the climatic mass-balance variability and climate sensitivity of 16 glaciers covering major mountain ranges in HMA. Generally, glaciers in the southeast have higher mass turnover while glaciers at the margins of HMA show higher interannual mass-balance variability. All glaciers are most sensitive to temperature perturbations in summer. The climatic mass balance of 15 glaciers is most sensitive to precipitation perturbations in summer or spring and summer, even if the seasonal accumulation peak is not in summer. Only one glacier's mass balance (Chhota Shigri Glacier) is most sensitive to precipitation perturbations in winter. Glaciers with high mass turnover and high summer-precipitation ratio are more sensitive to temperature perturbations. Sensitivity experiments reveal that besides the non-linearity of mass-balance temperature sensitivity, mass-balance precipitation sensitivity is non-linear as well. Furthermore, resolving the diurnal cycle of albedo, (re)freezing and the differentiation between liquid and solid precipitation are important to assess climate sensitivity of glaciers in HMA.

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

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

Icy thermometers: Quantifying the impact of volcanic heat on glacier elevation

Abstract We present a continentwide study of 600 glaciers located on and near 37 ice-clad volcanoes in South America. Results demonstrate glacier sensitivity to volcanic heat. We distinguished between “volcanic glaciers” (≤1 km from volcanic centers; n = 74), and “proximal glaciers” (1–15 km; n = 526) and calculated their equilibrium line altitudes (ELAs). For each ice-clad volcano, we compared the ELAs of its volcanic glaciers to those of its proximal glaciers, which showed that the ELAs of the former are higher than the ELAs of the latter. ΔELAmean, defined as the offset between the mean ELA of the volcanic glaciers compared with that of the proximal glaciers, was calculated for each ice-clad volcano. ΔELAmean was positive for 92% of the 37 volcanoes, and a quantitative relationship between ΔELAmean and volcanic thermal anomaly was established. Results highlight the impact of volcanic heat on glacier elevation; emphasize the need to exclude glaciers on, or near, volcanoes from glacier-climate investigations; and demonstrate the first-order potential for glaciers as “volcanic thermometers.” Volcanic-glacier monitoring could contribute to our understanding of magmatic and thermal activity, with changes in glacier geometries potentially reflecting long-term fluctuations in volcanic heat and unrest.

Long-term estimation of glacier mass balance using geospatial techniques in Western Himalayas, Ladakh, India

All glaciers are subject to mass fluctuations in the current context of climate change. For daily requirements like food, drink, irrigation, and the generation of hydroelectric power, these glaciers provide water to important basins including the Indus, Ganga, and Brahmaputra. Changes in glacier patterns are a blatant sign of local climate variability. Monitoring of glaciers requires long-term studies on glacier dynamics. Himalayan glaciers, because of their disposition in a complex topographic setting and inaccessible terrain render difficulty in the glacier observations in a continuous mode. Glacier mass fluctuations can be associated with glacier area shrinkage or expansion and concomitant snout shift. In the current study, two adjoining glaciers of different sizes, Pensilungpa and Drang Drung glaciers in the Zanskar Valley, Ladakh, India are selected. The period of the study was taken between the years 2000–2022. Earlier studies used a single day per year Accumulation Area Ratio (AAR) method to compute mass balance, which had limitations due to snow cover variability. The present study calculated and averaged all the AAR values for cloud-free images per year during the peak ablation period (mid-July to early September). Digital Elevation Model (DEM) difference technique was also employed for computing the mass budget between 2000 and 2021 b y utilizing two-time period DEMs. It was revealed that in the case of the AAR method, the Pensilungpa glacier showed 7 years of positive and 16 years of negative mass balance. The years 2003–2005 and 2011 to 2016 were depicted with negative mass balance with the highest value up to −0.752-m water equivalent (m.w.e.) for the year 2015. It has negligible areal fluctuations ranging from 0.01 to 0.6 km2. Drang Drung Glacier has shown 12 years of positive and 11 years of negative mass balance. The years 2002–2004 and 2009 to 2012 were depicted with positive mass balance with the highest value up to 0.305 m. w.e. Except, for the year 2009–2012 (areal increment ∼ 2.65 km2), years 2013–2015 showed a negative mass balance with negligible areal fluctuations. Mass balance estimation using DEM differencing method revealed an average estimated mass balance of −0.03 m. w.e. For Pensilungpa glacier though, it is 0.08 m. w.e. For Drang Drung glacier which shows good matches with the mass balance estimated using AAR method in m. w.e. Such contrasting behavior of mass balance suggests higher sensitivity of smaller glaciers to climate change.

Sensitivity of Glaciers in the European Alps to Anthropogenic Atmospheric Forcings: Case Study of the Argentière Glacier

AbstractThis study aims to quantify the contribution of anthropogenic forcings on the retreat of the Argentière Glacier (European Alps). The glacier evolution is simulated over 1850–2014 following retrospective scenarios produced with the IPSL‐CM6‐LR climate model, with and without natural and anthropogenic forcings. The scenarios used to force an ice flow model are statistically downscaled, preserving the long‐term trends and the physical consistency between precipitation and temperature. Since the late 19th century, the regional aerosol cooling has partially counteracted the greenhouse gas‐induced warming, delaying the time of emergence of the anthropogenic signal. The anthropogenic signal emerged from natural variability in 1979 for temperature and surface melting, and in 2008 for the glacier mass, whereas its snout position in 2014 remains compatible with natural variability. From the total mass loss between 1850 and 2014, 66% [21%–111%] is attributed to anthropogenic activities.

Melt rates in the kilometer-size grounding zone of Petermann Glacier, Greenland, before and during a retreat

Warming of the ocean waters surrounding Greenland plays a major role in driving glacier retreat and the contribution of glaciers to sea level rise. The melt rate at the junction of the ocean with grounded ice-or grounding line-is, however, not well known. Here, we employ a time series of satellite radar interferometry data from the German TanDEM-X mission, the Italian COSMO-SkyMed constellation, and the Finnish ICEYE constellation to document the grounding line migration and basal melt rates of Petermann Glacier, a major marine-based glacier of Northwest Greenland. We find that the grounding line migrates at tidal frequencies over a kilometer-wide (2 to 6 km) grounding zone, which is one order of magnitude larger than expected for grounding lines on a rigid bed. The highest ice shelf melt rates are recorded within the grounding zone with values from 60 ± 13 to 80 ± 15 m/y along laterally confined channels. As the grounding line retreated by 3.8 km in 2016 to 2022, it carved a cavity about 204 m in height where melt rates increased from 40 ± 11 m/y in 2016 to 2019 to 60 ± 15 m/y in 2020 to 2021. In 2022, the cavity remained open during the entire tidal cycle. Such high melt rates concentrated in kilometer-wide grounding zones contrast with the traditional plume model of grounding line melt which predicts zero melt. High rates of simulated basal melting in grounded glacier ice in numerical models will increase the glacier sensitivity to ocean warming and potentially double projections of sea level rise.

Grounding Zone of Amery Ice Shelf, Antarctica, From Differential Synthetic‐Aperture Radar Interferometry

AbstractWe employ a time series of Sentinel‐1 differential radar interferometry data from 2018 to detect the variability in grounding line position of the Fisher, Mellor, and Lambert glaciers, which drain about 47 billion tons of ice per year from East Antarctica. We observe kilometer‐scale tidal migration, two orders of magnitude larger than expected for ice flowing over a hard bed. The migration is not in phase with changes in oceanic tide. In two estuaries underlaid by subglacial channels, we observe two states of migration that switch on and off over time scales of several weeks. The range of vertical motion reveals a water column thickness of 2–20 cm. Such intrusions of seawater over wide grounding zones are not accounted for in physical models. Including them will add vigorous melting of grounded ice that will enhance the sensitivity of glaciers to ocean warming and increase projections of mass loss.

Characterizing 4 decades of accelerated glacial mass loss in the west Nyainqentanglha Range of the Tibetan Plateau

Abstract. Glacier retreat is altering the water regime of the Tibetan Plateau (TP) as the region's climate changes, but there remain substantial gaps in our knowledge of recent glacier loss in this region due to the difficulty of making direct high-mountain observations, and this limits our ability to predict the future of this important water resource. Here, we assessed 44 years of glacier area and volume changes in the major west Nyainqentanglha Range (WNR) that supplies meltwater to the densely populated Lhasa River basin and Nam Co, the second largest endorheic lake on the TP. Between the two periods 1976–2000 and 2000–2020, we found that the glacier areal retreat rate more than doubled (from -0.54±0.21 % a−1 to -1.17±0.30 % a−1), and surface lowering also accelerated (from -0.26±0.09 to -0.37±0.15 m w.e a−1) with particularly intense melting after 2014. This acceleration is similar in both timing and magnitude to that observed for Himalayan glaciers farther south. Besides, the areal retreat rate and mass loss rate of most glaciers in the WNR were not synchronized. To understand the sensitivity of WNR glaciers to climate forcing, we examined the effects of topography, debris cover and the presence of proglacial lakes on our observed changes. We found consistently faster areal retreat but slower thinning rates on steeper slopes and an inconsistent relationship with aspect. We concluded that our observed spatial and temporal patterns of glacier change were dominated by observed local variations in temperature and precipitation, the melt-reducing role of supraglacial debris, and the increasing influence of ice-marginal lakes on glacier ablation.

Hydrological and dynamical response of glaciers to climate change based on their dimensions in the Hunza Basin, Karakoram

Glaciers of different dimensions respond differently to climate change, resulting in variations in glacier dynamics and runoff. Differentiation of these responses is critical for the Karakoram region (in context to Karakoram anomalies) where glaciers contribute significantly to runoff. Herein, the Open Global Glacier Model is used to quantify these variabilities in the Hunza basin, and thereby develop a comprehensive understanding of how glaciers respond to past and future climate change. Basin glaciers were classified into six classes based on their terminus elevation and area (Z1-Z6). Annual mass balance (MB) time series were reconstructed from 1960 to 2019. The results indicate that the average MB is −0.09 ± 0.21 m w.e.a−1, which has been accelerated in 2000 s (average: −0.16 ± 0.20 m w.e.a−1). Cumulative MB between classes varies from −4.55 m w.e. (Z1) to −5.92 m w.e. (Z3), indicating that the medium classes (Z3, Z4) glaciers MB is comparatively more negative. Monthly glacier runoff explains the sensitivity of small glaciers to summer temperature, as they only contribute to runoff in the summer season. However, glacier runoff per unit area per year remains almost the same across these groups. Future climate change scenarios under CMIP6 illustrate that small (Z5/Z6) and large (Z1) glaciers will lose up to 90 % and 10 % of their volume, area, and length, respectively. The results identified that basin glacier runoff will increase till the year 2060 and will start decreasing after that to 2100. Projected glacier runoff suggests that the Basin runoff is mediated by Z4 glaciers. Whereas, the peak water supply from small size glaciers has occurred in past (Z6) or would occur in near future (Z5) while large size glaciers (Z1-Z3) runoff keeps on increasing till 2100. These findings indicate that immediate mitigation measures are required to deal with glacier change and ensure long-term water security in this region.

Lateglacial paleoglacier and paleoclimate reconstructions in the north-western Italian Alps

Lateglacial (19.0–11.7 ka ago) paleo-temperature records in the Western European Alps document several short-term cooling episodes within the general post-Last Glacial Maximum warming trend, in phase with North Hemisphere climatic oscillations. Alpine paleo-precipitation reconstructions are instead rare, and further constraints are needed in order to assess whether Lateglacial cold periods were associated with a modified atmospheric circulation pattern over the European Alps. The Alpine paleoglacial record offers a quantitative framework to investigate Lateglacial paleoclimatic conditions and glacier sensitivity in response to both temperature and precipitation changes. Through the combination of 10Be surface-exposure dating of glacial landforms and deposits constraining ice front and surface, together with numerical glacier simulations (iSOSIA), our study aims to reconstruct in space and time the main Lateglacial ice stages and associated paleo-climatic conditions in three tributary valleys (Valpelline, Valsavarenche and Val di Cogne) located within the Dora Baltea catchment (north-western Italian Alps). Our dating-modelling approach reveals in all the three investigated sectors two distinct paleoglacier stages at ca. 13 and 11 ka, documenting respectively the ice configurations at the transition between the Oldest Dryas cold period and the Bølling-Allerød interstadial, and between the Younger Dryas cold period and the early Holocene warming. Numerical ice-simulation outcomes suggest a similar-to-today precipitation pattern during the two ice stages, with either same absolute or homogeneously decreased precipitation values over the Dora Baltea catchment, although a unique quantitative solution of paleo-precipitation magnitudes could not be constrained from our dataset. Using present-day precipitation pattern and magnitude, our results provide paleo-temperature offsets from present-day between −3.3 and −3.8 °C for the older glacial stage, and −2.7 to −3.2 °C for the younger glacial stage, coinciding with the upper range of paleo-temperature reconstructions from other paleoclimatic proxies. Finally, Alpine glaciers’ sensitivity to climate fluctuations differ significantly between the investigated catchments, with a much higher glacier sensitivity to changes in the Equilibrium Line Altitude in the northern (Valpelline) compared to the southern (Valsavarenche and Val di Cogne) tributaries, reflecting different topographic and/or climatic conditions between the three valleys.

Modelled sensitivity of Monte San Lorenzo ice cap, Patagonian Andes, to past and present climate

Sparse measurements of glacier mass balance, velocity and ice thickness in Patagonia challenge our ability to understand glacier sensitivity to climate change and relate past glacier fluctuations to palaeoclimate change. Small ice caps, such as Monte San Lorenzo, have short response times and high climate sensitivity, making well-dated moraines in their glacier foregrounds an important tool for exploring glacier response to rapid changes in palaeoclimate. Here, the Parallel Ice Sheet Model (PISM) is used to model ice flow across a domain centred on the Monte San Lorenzo ice cap. Ice-flow parameters are calibrated to match present-day ice extent, velocity and thickness. Our aim is, firstly, to quantify present-day physical glacier properties, and ice cap dynamics and sensitivities, and secondarily, to evaluate the controls on the deglaciation of the ice cap within the context of the Southern Hemisphere palaeoclimate system during the Last Glacial-Interglacial Transition (LGIT). The simulated present-day ice cap shows high surface mass flux, with ablation at outlet glacier tongues up to 18 m w. e. a−1, accumulation at the highest elevations of up to 5.5 m w. e. a−1 and a simulated Equilibrium Line Altitude (ELA) of 1750–2000 m asl. The ice cap is more sensitive to changes in precipitation relative to changes in temperature. We provide envelopes with likely ranges of palaeotemperature and palaeoprecipitation for glacial advances to moraines formed during the Last Glacial-Interglacial Transition and Holocene. Our numerical model predicts that cooling and an increase in precipitation is required to force glacial advance to mapped moraine limits at 12.1 ka (2°C cooler, 50% more precipitation), 5.6 ka (0°C cooler, 50% more precipitation) and 0.2 ka (1°C cooler, 25% more precipitation). Our modelling results thus provide insights into the present-day mass balance, thermal regime and velocity of the ice cap, explores the sensitivities of this ice cap to various model and climatic parameters, and provide palaeoclimatic envelopes for readvances during the LGIT and Holocene in Patagonia.

GlacierNet2: A hybrid Multi-Model learning architecture for alpine glacier mapping

In recent decades, climate change has significantly affected glacier dynamics, resulting in mass loss and an increased risk of glacier-related hazards including supraglacial and proglacial lake development, as well as catastrophic outburst flooding. Rapidly changing conditions dictate the need for continuous and detailed observations and analysis of climate-glacier dynamics. Thematic and quantitative information regarding glacier geometry is fundamental for understanding climate forcing and the sensitivity of glaciers to climate change, however, accurately mapping debris-cover glaciers (DCGs) is notoriously difficult based upon the use of spectral information and conventional machine-learning techniques. The objective of this research is to improve upon an earlier proposed deep-learning-based approach, GlacierNet, which was developed to exploit a convolutional neural-network segmentation model to accurately outline regional DCG ablation zones. Specifically, we developed an enhanced GlacierNet2 architecture thatincorporates multiple models, automatic post-processing, and basin-level hydrological flow techniques to improve the mapping of DCGs such that it includes both the ablation and accumulation zones. Experimental evaluations demonstrate that GlacierNet2 improves the estimation of the ablation zone and allows a high level of intersection over union (IOU: 0.8839) score. The proposed architecture provides complete glacier (both accumulation and ablation zone) outlines at regional scales, with an overall IOU score of 0.8619. This is a crucial first step in automating complete glacier mapping that can be used for accurate glacier modeling or mass-balance analysis.

Modeling the climate sensitivity of Patagonian glaciers and their responses to climatic change during the global last glacial maximum

Investigation of the behavior of the former ice sheet over Patagonia aids better understanding of ice-climate interactions and has important implications for deciphering how modern glaciers will respond to rapid increase in global temperature. Here, we use a 1-km resolution ice sheet model to identify the climate sensitivity of Patagonian glaciers and examine their responses to climatic change during the global Last Glacial Maximum (gLGM). Our results demonstrate that the total glacier area increases by ∼78 × 103 km2 and the equilibrium-line altitude (ELA) lowers by ∼163 m for every 1 °C of cooling under modern precipitation regime. Keeping temperature unchanged, there is an increase of total glacier area by ∼21 × 103 km2 and a ΔELA by ∼64 m for every doubling in precipitation. According to the multimodel ensemble mean of 21 PMIP models, an overall colder and drier climate prevails over Patagonia during the gLGM, with a decrease of annual mean temperature and precipitation by ∼4.7 °C and 12%, respectively. Under the modeled gLGM climate, there is an extensive ice sheet (∼387 × 103 km2) almost completely covering the Patagonian Andes, which results largely from the cooling with positive contribution from sea-level fall. The Patagonian ice sheet is drained by ice streams at the western margins and fast-flowing outlet glaciers to the east, with a north-to-south ice divide mainly extending the southern Patagonian Andes. Additionally, the erosion potential induced by the ice sheet exhibits a very strong localization over the fjords and valleys, resembling the pattern of ice velocity. The modeled ice sheet extent and ice flow pattern during the gLGM match well with the latest empirical reconstructions (though with spatial discrepancies), whereas the total ice volume is underestimated. However, the modeled Patagonian ice sheet exhibits high sensitivity to climatic forcing and the values of ice sheet model parameters used.

Modeling the climate sensitivity of Patagonian glaciers and their responses to climatic change during the global last glacial maximum

Modeling the climate sensitivity of Patagonian glaciers and their responses to climatic change during the global last glacial maximum

Revisiting glacier mass-balance sensitivity to surface air temperature using a data-driven regionalization

AbstractThis study involves examination of glaciological mass-balance time series, glacier and climatic descriptors, the application of machine learning methods for glaciological clustering, and computation of mass-balance time series based upon the clustering and statistical analyses relative to gridded air temperature datasets. Our analysis revealed an increasingly coherent mass-balance trend but a latitudinal bias of monitoring programs. The glacier classification scheme delivered three clusters, suggesting these correspond to climate-based first-order regimes, as glacier morphometric characteristics weighed little in our multivariate analysis. We combined all available surface mass-balance data from in situ monitoring programs to study temperature sensitivity for each cluster. These aggregated mass-balance time series delivered spatially different statistical relationships to temperature. Results also showed that surface mass balance tends to have a temporal self-correlation of ~20 years. Using this temporal window to analyze sensitivity since ~ 1950, we found that in all cases temperature sensitivity, while generally negative, tended to fluctuate through time, with the largest absolute magnitudes occurring in the 1980s and becoming less negative in recent years, revealing that glacier sensitivity is non-stationary. These findings point to a scenario of a coherent signal of change no matter the glacier regime. This work provides new insights into glacier–climate relationships that can guide observational and analytical strategies.

Quantifying Geodetic Mass Balance of the Northern and Southern Patagonian Icefields Since 1976

Southern Andean glaciers contribute substantially to global sea-level rise. Unfortunately, mass balance estimates prior to 2000 are limited, hindering our understanding of the evolution of glacier mass changes over time. Elevation changes over 1976/1979 to 2000 derived from historical KH-9 Hexagon imagery and NASADEM provide the basis for geodetic mass balance estimates for subsets of the Northern Patagonian Icefield (NPI) and the Southern Patagonian Icefield (SPI), extending current mass balance observations by ∼20 years. Geodetic mass balances were −0.63 ± 0.03 m w.e. yr−1 for 63% of the NPI and −0.33 ± 0.05 m w.e. yr−1 for 52% of the SPI glacierized areas for this historical period. We also extend previous estimates temporally by 25% using NASADEM and ASTER elevation trends for the period 2000 to 2020, and find geodetic mass balances of −0.86 ± 0.03 m w.e. yr−1 for 100% of the NPI and −1.23 ± 0.04 m w.e. yr−1 for 97% of the SPI glacierized areas. 2000–2020 aggregations for the same areas represented in the 1976/1979 to 2000 estimates are −0.78 ± 0.03 m w.e. yr−1 in the NPI and −0.80 ± 0.04 m w.e. yr−1 on the SPI. The significant difference in SPI geodetic mass balance in the modern period for 100% vs. 52% of the glacierized area suggests subsampling leads to significant biases in regional mass balance estimates. When we compare the same areas in each time period, the results highlight an acceleration of ice loss by a factor of 1.2 on the NPI and 2.4 on the SPI in the 21st century as compared to the 1976/1979 to 2000 period. While lake-terminating glaciers show the most significant increase in mass loss rate from 1976/1979–2000 to 2000–2020, mass balance trends are highly variable within glaciers of all terminus environments, which suggests that individual glacier sensitivity to climate change is dependent on a multitude of morphological and climatological factors.