On the Imbalance and Response Time of Glaciers in the European Alps

Zekollari, Harry; Huss, Matthias; Farinotti, Daniel

doi:10.1029/2019gl085578

Cited by 52 publications

(48 citation statements)

References 52 publications

(85 reference statements)

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“…Possible interpretations are that the mean slope and the mass transfer are related, with steeper glaciers having faster dynamics and, that glaciers with higher accumulation areas (i.e., still having a wide accumulation zone) have lower mass balance sensitivity. This hypothesis would imply that steeper glaciers with wide accumulation area faster reach a balanced-state with less negative mass balances while glaciers with low slope remain imbalanced for a longer time, experiencing more negative mass balances to adapt to changing climatic conditions (corroborated by e.g., Brun et al, 2019;Zekollari et al, 2020).…”

Section: Representativeness Of In Situ Monitored Mass Changementioning

confidence: 99%

Region-Wide Annual Glacier Surface Mass Balance for the European Alps From 2000 to 2016

et al. 2020

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Studying glacier mass changes at regional scale provides critical insights into the impact of climate change on glacierized regions, but is impractical using in situ estimates alone due to logistical and human constraints. We present annual mass-balance time series for 239 glaciers in the European Alps, using optical satellite images for the period of 2000 to 2016. Our approach, called the SLA-method, is based on the estimation of the glacier snowline altitude (SLA) for each year combined with the geodetic mass balance over the study period to derive the annual mass balance. In situ annual mass-balances from 23 glaciers were used to validate our approach and underline its robustness to generate annual mass-balance time series. Such temporally-resolved observations provide a unique potential to investigate the behavior of glaciers in regions where few or no data are available. At the European Alps scale, our geodetic estimate was performed for 361 glaciers (75% of the glacierized area) and indicates a mean annual mass loss of −0.74 ± 0.20 m w.e. yr −1 from 2000 to 2016. The spatial variability in the average glacier mass loss is significantly correlated to three morpho-topographic variables (mean glacier slope, median, and maximum altitudes), altogether explaining 36% of the observed variance. Comparing the mass losses from in situ and SLAmethod estimates and taking into account the glacier slope and maximum elevation, we show that steeper glaciers and glaciers with higher maximum elevation experienced less mass loss. Because steeper glaciers (>20 •) are poorly represented by in situ estimates, we suggest that region-wide extrapolation of field measurements could be improved by including a morpho-topographic dependency. The analysis of the annual mass changes with regard to a global atmospheric dataset (ERA5) showed that: (i) extreme climate events are registered by all glaciers across the European Alps, and we identified opposite weather regimes favorable or detrimental to the mass change; (ii) the interannual variability of glacier mass balances in the "central European Alps" is lower; and (iii) current strong imbalance of glaciers in the European Alps is likely mainly the consequence of the multi-decadal increasing trend in atmospheric temperature, clearly documented from ERA5 data.

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Section: Representativeness Of In Situ Monitored Mass Changementioning

confidence: 99%

Region-Wide Annual Glacier Surface Mass Balance for the European Alps From 2000 to 2016

et al. 2020

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“…Similar evolutions of runoff under RCP4.5 and RCP8.5 are also linked more generally to the glacier evolutions. The latter are very similar under both RCPs in the first decades of the century, and are largely driven by the recent and present-day glacier geometry, because of the large inertia of glaciers, inducing a lag between temperature changes and their response 40 . A last explanation is that temperature and precipitation evolutions are quite similar under RCP4.5 and RCP8.5, with differences only appearing in the second part of the twenty-first century 17 .…”

Section: Contribution Of Snow and Ice Melt To Water Dischargementioning

confidence: 91%

The impact of climate change and glacier mass loss on the hydrology in the Mont-Blanc massif

Laurent

Buoncristiani

Pohl

et al. 2020

Sci Rep

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The Mont-Blanc massif, being iconic with its large glaciers and peaks of over 4,000 m, will experience a sharp increase in summer temperatures during the twenty-first century. By 2100, the impact of climate change on the cryosphere and hydrosphere in the Alps is expected to lead to a decrease in annual river discharge. In this work, we modelled the twenty-first century evolution of runoff in the Arve river, downstream of Mont-Blanc's French side. For the first time for this region, we have forced a hydrological model with output from an ice-dynamical glacier model and 16 downscaled climate projections, under RCP4.5 and RCP8.5 scenarios. By 2100, under RCP8.5 (high-emission scenario), the winter discharge of the Arve river remains low but is expected to increase by 80% when compared to the beginning of the century. By contrast, the summer season, currently the most important discharge period, will be marked by a runoff decrease of approximately 40%. These changes are almost similar according to a scenario with a lower warming (RCP4.5) and are mostly driven by glacier retreat. These shifts will have significant downstream impacts on water quantity and quality, affecting hydroelectric generation, agriculture, forestry, tourism and aquatic ecosystems. Global change and temperature increase are projected to lead to major environmental changes in mountainous regions 1 , including major changes in glacier extent 2,3 , permafrost 4 , ice and snow cover 5-7 , and vegetation 8,9. In the Alps, the cryosphere is crucial for water storage and for contributing to the total discharge of the main major European rivers 10. In this context, major changes are likely to occur in water discharge 11 in and near these vulnerable regions, mostly decreasing runoff in summer and modifying water resources 12. These changes could either be driven by (i) changes in precipitation 13,14 , especially in the proportion of liquid and solid water 15,16 , depending on the altitude of the 0 °C isotherm 17 ; (ii) a general warming trend, increasing snow and ice melt, hereby contributing to glacier mass loss 18 , but also increasing evapotranspiration from the surface; (iii) glacier retreat in response to such warming, ultimately leading to changes in water discharge as the available ice reserves gradually decrease 11. Of particular importance are the relative weight of each of these forcings over the coming years and decades, and their dependency on the greenhouse gas emission scenarios. These changes will have major effects on river discharges and water quality 19 , impacting hydropower generation, agriculture, forestry, tourism and aquatic ecosystems 8,20. Many studies have explored the impact of global warming and glacier retreat on glacier runoff, at global 21 and regional scales (e.g., High Mountain Asia 22,23 , the Andes 24,25 and the USA 26). In the European Alps, glacier runoff evolution under climate change has already been investigated in Switzerland 27,28 and Austria 29 for example. In the French Alps, assessments of future changes are sca...

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“…Moreover, glacier geometry changes are themselves an indicator of local (for individual glaciers) and regional (for glaciers considered across a wider area) climate changes (Oerlemans, 1986(Oerlemans, , 2005. Direct observations of historical glacier geometry (observations of contemporaneous glacier extent, as opposed to secondary sources like moraines or lake sediments) are relatively sparse (Zemp et al, 2015;Cogley, 2009), and it is only through recent aerial (WGMS and NSIDC, 1989) and satellite mapping (RGI Consortium, 2017) that fairly comprehensive inventories of glaciers across all of the world's glacierised regions have become available, cataloguing upwards of 200 000 glaciers. Even this number is likely a significant underestimate (Parkes and Marzeion, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…OGGM by default calibrates the glacier sensitivity to local temperature based on CRU TS 4.01 data (Harris et al, 2020) that begins in 1901, and uses RGI version 6.0 (RGI Consortium, 2017) glacier outlines which are typically from around the start of the 21st century. In many regions, glaciers were already experiencing significant retreat by the beginning of the 20th century (Zemp et al, 2015), and calibrating glacier models for time periods when glaciers are far from equilibrium brings additional challenges. It is a critical test of a model's ability to determine whether it can reach non-trivial equilibrium states in periods of more stable climate because recent retreats and expected future sustained retreats necessarily exist as transitional phenomena between equilibria.…”

Section: Introductionmentioning

confidence: 99%

Modelling regional glacier length changes over the last millennium using the Open Global Glacier Model

Parkes

Goosse

2020

The Cryosphere

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Abstract. A large majority of the direct observational record for glacier changes falls within the industrial period, from the 19th century onward, associated with global glacier retreat. Given this availability of data and the significant focus in contemporary glacier modelling falling on recent retreat, glacier models are typically calibrated using – and validated with – only observations of glaciers that are considerably out of equilibrium. In order to develop a broader picture of the skill of one glacier model – the Open Global Glacier Model (OGGM) – we model glaciers for extended historical timescales of 850–2004 CE using a selection of six general circulation model (GCM) outputs. We select glaciers for which long-term length observations are available in order to compare these observations with the model results, and we find glaciers with such observations in almost all glacierised regions globally. In many regions, the mean modelled glacier changes are consistent with observations, with recent observed retreat in these regions typically at the steeper end of the range of modelled retreats. However, on the scale of individual glaciers, performance of the model is worse, with overall correlation between observed and modelled retreat weak for all of the GCM datasets used to force the model. We also model the same set of glaciers using modified climate time series from each of the six GCMs that keep temperature or precipitation constant, testing the impact of each individually. Temperature typically explains considerably more variance in glacier lengths than precipitation, but results suggest that the interaction between the two is also significant within OGGM and neither can be seen as a simple proxy for glacier length changes. OGGM proves capable of reproducing recent observational trends on at least a qualitative level in many regions, with a modelling period over a considerably larger timescale than it is calibrated for. Prospects are good for more widespread use of OGGM for timescales extending to the pre-industrial period, where glaciers were typically larger and experience less rapid (and less globally consistent) geometry changes, but additional calibration will be required in order to have confidence in the magnitude of modelled changes, particularly on the scale of individual glaciers.

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On the Imbalance and Response Time of Glaciers in the European Alps

Cited by 52 publications

References 52 publications

Region-Wide Annual Glacier Surface Mass Balance for the European Alps From 2000 to 2016

Region-Wide Annual Glacier Surface Mass Balance for the European Alps From 2000 to 2016

The impact of climate change and glacier mass loss on the hydrology in the Mont-Blanc massif

Modelling regional glacier length changes over the last millennium using the Open Global Glacier Model

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