scholarly journals Darkening Swiss glacier ice?

2018 ◽  
Author(s):  
Kathrin Naegeli ◽  
Matthias Huss ◽  
Martin Hoelzle
Keyword(s):  
Temporal Trend ◽  
Spatial Scales ◽  
Swiss Alps ◽  
Limited Region ◽  
Albedo Feedback ◽  
Glacier Melt ◽  
Glacier Ice ◽  
Wide Scale ◽  
Near Future ◽  
Scientific Debates

Abstract. The albedo feedback is an important driver of glacier melt over bare-ice surfaces. Light-absorbing impurities strongly enhance glacier melt rates but their abundance, composition and variations in space and time are subject to considerable uncertainties and on-going scientific debates. In this study, we assess the temporal evolution of shortwave broadband albedo derived from 19 end-of summer Landsat scenes for the bare-ice areas of 39 large glaciers in the western and southern Swiss Alps. Trends in bare-ice albedo crucially depend on the spatial scale considered. No significant negative temporal trend in bare-ice albedo was found on a regional to glacier-wide scale. However, at higher spatial scales, certain areas of bare-ice including the lowermost elevations and margins of the ablation zones revealed significant darkening over the study period 1999 to 2016. A total glacier area of 16 km2 (equivalent to about 12 % of the average end-of-summer bare-ice area in the study area) exhibited albedo trends significant at the 95 % confidence level or higher. Most of this area was affected by a negative albedo trend of about −0.05 per decade. Generally, bare-ice albedo exhibits a strong interannual variability, caused by a complex interplay of meteorological conditions prior to the acquisition of the data, local glacier characteristics and the date of the investigated satellite imagery. Although, a darkening of glacier ice was found to be present over only a limited region, we emphasise that due to the recent and projected growth of bare-ice areas and prolongation of the ablation season in the region, the albedo feedback will considerably enhance the rate of glacier mass loss in the Swiss Alps in the near future.

scholarly journals Change detection of bare-ice albedo in the Swiss Alps

2019 ◽  
Vol 13 (1) ◽  
pp. 397-412 ◽  
Author(s):  
Kathrin Naegeli ◽  
Matthias Huss ◽  
Martin Hoelzle
Keyword(s):  
Temporal Trend ◽  
Spatial Scales ◽  
Swiss Alps ◽  
Limited Region ◽  
Albedo Feedback ◽  
Glacier Melt ◽  
Glacier Ice ◽  
Wide Scale ◽  
Near Future ◽  
Scientific Debates

Abstract. Albedo feedback is an important driver of glacier melt over bare-ice surfaces. Light-absorbing impurities strongly enhance glacier melt rates but their abundance, composition and variations in space and time are subject to considerable uncertainties and ongoing scientific debates. In this study, we assess the temporal evolution of shortwave broadband albedo derived from 15 end-of-summer Landsat scenes for the bare-ice areas of 39 large glaciers in the western and southern Swiss Alps. Trends in bare-ice albedo crucially depend on the spatial scale considered. No significant negative temporal trend in bare-ice albedo was found on a regional to glacier-wide scale. However, at higher spatial scales, certain areas of bare ice, including the lowermost elevations and margins of the ablation zones, revealed significant darkening over the study period 1999 to 2016. A total glacier area of 13.5 km2 (equivalent to about 12 % of the average end-of-summer bare-ice area in the study area) exhibited albedo trends significant at the 95 % confidence level or higher. Most of this area was affected by a negative albedo trend of about −0.05 decade−1. Generally, bare-ice albedo exhibits a strong interannual variability, caused by a complex interplay of meteorological conditions prior to the acquisition of the data, local glacier characteristics and the date of the investigated satellite imagery. Although a darkening of glacier ice was found to be present over only a limited region, we emphasize that due to the recent and projected growth of bare-ice areas and prolongation of the ablation season in the region, the albedo feedback will considerably enhance the rate of glacier mass loss in the Swiss Alps in the near future.

scholarly journals On the effect of short-term climate variability on mountain glaciers: insights from a case study

2013 ◽  
Vol 59 (217) ◽  
pp. 992-1006 ◽  
Author(s):  
Daniel Farinotti
Keyword(s):  
Climatic Variability ◽  
Swiss Alps ◽  
Ice Dynamics ◽  
Mountain Glaciers ◽  
Temperature And Precipitation ◽  
Glacier Ice ◽  
Long Term Trends ◽  
Model Set ◽  
Set Up

AbstractStudies addressing the response of glaciers to climate change have so far analyzed the effect of long-term trends in a particular set of meteorological variables only, implicitly assuming an unaltered climatic variability. Here a framework for distinguishing between year-to-year, month-to-month and day-to-day variability is proposed. Synthetically generated temperature and precipitation time series following the same long-term trend but with altered variability are then used to force an ice-dynamics model set up for Rhonegletscher, Swiss Alps. In the case of temperature, variations in the day-to-day variability are shown to have a larger effect than changes at the yearly scale, while in the case of precipitation, variability changes are assessed as having negligible impact. A first set of scenarios is used to show that compared to reference, doubling the temperature variability can reduce glacier ice volume by up to 64% within half a decade. A second set derived from the results of the European ENSEMBLES project, however, shows that such changes are expected to remain below 8% even for extreme scenarios. Although the latter results relativize the importance of the effect in the near future, the analyses indicate that at least caution is required when assuming ‘unchanged variability’.

scholarly journals Distributed snow and rock temperature modelling in steep rock walls using Alpine3D

2017 ◽  
Vol 11 (1) ◽  
pp. 585-607 ◽  
Author(s):  
Anna Haberkorn ◽  
Nander Wever ◽  
Martin Hoelzle ◽  
Marcia Phillips ◽  
Robert Kenner ◽  
...  
Keyword(s):  
Energy Balance ◽  
Snow Cover ◽  
Snow Depth ◽  
Spatial Scales ◽  
Swiss Alps ◽  
Balance Model ◽  
Near Surface ◽  
Surface Rock ◽  
Depth Data ◽  
Rock Temperature

Abstract. In this study we modelled the influence of the spatially and temporally heterogeneous snow cover on the surface energy balance and thus on rock temperatures in two rugged, steep rock walls on the Gemsstock ridge in the central Swiss Alps. The heterogeneous snow depth distribution in the rock walls was introduced to the distributed, process-based energy balance model Alpine3D with a precipitation scaling method based on snow depth data measured by terrestrial laser scanning. The influence of the snow cover on rock temperatures was investigated by comparing a snow-covered model scenario (precipitation input provided by precipitation scaling) with a snow-free (zero precipitation input) one. Model uncertainties are discussed and evaluated at both the point and spatial scales against 22 near-surface rock temperature measurements and high-resolution snow depth data from winter terrestrial laser scans.In the rough rock walls, the heterogeneously distributed snow cover was moderately well reproduced by Alpine3D with mean absolute errors ranging between 0.31 and 0.81 m. However, snow cover duration was reproduced well and, consequently, near-surface rock temperatures were modelled convincingly. Uncertainties in rock temperature modelling were found to be around 1.6 °C. Errors in snow cover modelling and hence in rock temperature simulations are explained by inadequate snow settlement due to linear precipitation scaling, missing lateral heat fluxes in the rock, and by errors caused by interpolation of shortwave radiation, wind and air temperature into the rock walls.Mean annual near-surface rock temperature increases were both measured and modelled in the steep rock walls as a consequence of a thick, long-lasting snow cover. Rock temperatures were 1.3–2.5 °C higher in the shaded and sunny rock walls, while comparing snow-covered to snow-free simulations. This helps to assess the potential error made in ground temperature modelling when neglecting snow in steep bedrock.

scholarly journals Towards radiocarbon dating of ice cores

2009 ◽  
Vol 55 (194) ◽  
pp. 985-996 ◽  
Author(s):  
M. Sigl ◽  
T.M. Jenk ◽  
T. Kellerhals ◽  
S. Szidat ◽  
H.W. Gäggeler ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Ice Core ◽  
Ice Cores ◽  
Swiss Alps ◽  
Carbonaceous Aerosol ◽  
Polar Ice ◽  
Low Latitude ◽  
Bolivian Andes ◽  
Glacier Ice ◽  
Dating Method

AbstractA recently developed dating method for glacier ice, based on the analysis of radiocarbon in carbonaceous aerosol particles, is thoroughly investigated. We discuss the potential of this method to achieve a reliable dating using examples from a mid- and a low-latitude ice core. Two series of samples from Colle Gnifetti (4450 m a.s.l., Swiss Alps) and Nevado Illimani (6300 m a.s.l., Bolivian Andes) demonstrate that the 14C ages deduced from the water-insoluble organic carbon fraction represent the age of the ice. Sample sizes ranged between 7 and 100 μg carbon. For validation we compare our results with those from independent dating. This new method is thought to have major implications for dating non-polar ice cores in the future, as it provides complementary age information for time periods not accessible with common dating techniques.

Time-Life, World Reporter and the secretary: experiments with end-users

1986 ◽  
Vol 12 (4) ◽  
pp. 167-175 ◽  
Author(s):  
David Nicholas ◽  
Kevin Harris ◽  
Gertrud Erbach
Keyword(s):  
Information Retrieval ◽  
Information Seeking ◽  
Information Source ◽  
End Users ◽  
End User ◽  
Training Time ◽  
Wide Scale ◽  
Time To Learn ◽  
Information Retrieval Methods ◽  
Near Future

After six months of training Time-Life book researchers to use online databases it is clear that they will not become end-users overnight—despite plentiful training, good facilities, user-friendly interfaces and the like. The reasons for this are less clear but high on the list come: a lack of time (to learn and maintain the necessary searching skills); a general reluctance to abandon the tried and tested—and often pleasurable—con ventional information retrieval methods (there is certainly nothing to suggest that the computer is going to replace the telephone as an information source); and the low priority given to the (formal) information-seeking component of the job (high priority being given to the more visible and pressing elements, like writing and commissioning pictures). There is little in Time-Life's online experience to lend support to the belief that there will be wide-scale end-user searching in the near future. Online will find its place in the array of information retrieval methods at the disposal of the user and will undoubtedly be used where manual methods have failed: it is unlikely, however, to supplant manual systems that work well and are well-liked. Secretaries do appear to be well-qualified, and in an excel lent position to become a major end-user group and might indeed pose a threat to the librarian intermediary in the near future.

scholarly journals Sensitivity of mountain glacier mass balance to changes in bare-ice albedo

2017 ◽  
Vol 58 (75pt2) ◽  
pp. 119-129 ◽  
Author(s):  
Kathrin Naegeli ◽  
Matthias Huss
Keyword(s):  
Mass Balance ◽  
Balance Model ◽  
Glacier Mass Balance ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Mountain Glacier ◽  
Albedo Feedback ◽  
In Situ Data ◽  
The Impact ◽  
Near Future

ABSTRACT Albedo is an important parameter in the energy balance of bare-ice surfaces and modulates glacier melt rates. The prolongation of the ablation period enforces the albedo feedback and highlights the need for profound knowledge on impacts of bare-ice albedo on glacier mass balance. In this study, we assess the mass balance sensitivity of 12 Swiss glaciers with abundant long-term in-situ data on changes in bare-ice albedo. We use pixel-based bare-ice albedo derived from Landsat 8. A distributed mass-balance model is applied to the period 1997–2016 and experiments are performed to assess the impact of albedo changes on glacier mass balance. Our results indicate that glacier-wide mass-balance sensitivities to changes in bare-ice albedo correlate strongly with mean annual mass balances (r 2 = 0.81). Large alpine glaciers react more sensitively to bare-ice albedo changes due to their ablation areas being situated at lower elevations. We find average sensitivities of glacier-wide mass balance of −0.14 m w.e. a−1 per 0.1 albedo decrease. Although this value is considerably smaller than sensitivity to air temperature change, we stress the importance of the enhanced albedo feedback that will be amplified due to atmospheric warming and a suspected darkening of glacier surface in the near future.

Post-glacial dynamics of alpine Little Ice Age glacitectonized frozen landforms (Swiss Alps)

2020 ◽  
Author(s):  
Julie Wee ◽  
Reynald Delaloye ◽  
Chloé Barboux
Keyword(s):  
Little Ice Age ◽  
Spatial Configuration ◽  
Sar Interferometry ◽  
Swiss Alps ◽  
Ice Age ◽  
Permafrost Degradation ◽  
Mass Wasting ◽  
Ground Ice ◽  
Slope Movements ◽  
Glacier Ice

<p>Glaciers and frozen debris landforms have coexisted and episodically interacted throughout the Holocene, the former having altered the development, spatial distribution and thermal regime of the latter. In the Alps, the apogee of last interaction phase occurred during the Little Ice Age (LIA). Since then, due to glacier shrinkage, interactions between glaciers and LIA pre-existing frozen debris have gradually diminished and are leaning towards being non-existent. Post-LIA glacier forefields in permafrost environments, including associated glacitectonized frozen landforms (GFL) have shifted from a thermal and mechanical glacier dominant regime towards a periglacial or even post-periglacial regime. GFL are undergoing thermal and mechanical readjustments in response to both the longer-term glacier recession and the more recent drastic climatic warming. They can be expressed by a combination of mass-wasting processes and thaw-induced subsidence.</p><p> </p><p>In various regions of the Swiss Alps, slope movements occurring in a periglacial context have been inventoried in previous works using differential SAR interferometry (DInSAR) (Barboux et al., 2014). In the scope of this study, and focusing solely on mass-wasting GFL, the former inventory allowed the identification of the latter under various spatial configurations within LIA glacier forefields. While most observed GFL are disconnected from the associated glacier, some are still connected. Additionally, ground ice occurs as interstitial or massive (buried) glacier ice. This potentially infers the ongoing of non-uniform morphodynamical readjustments.</p><p> </p><p>To understand the site-specific behaviour of GFL, the analysis of long-term time-series of permafrost monitoring and multi-temporal high-resolution Digital Elevation Models will allow the assessment of the recent evolution of the Aget and Ritord/Challand LIA glacier forefields (46°00’32’’ N, 7°14’20’’ E and 45°57’10’’ N, 7°14’52’’ E, respectively) and their associated GFL (i.e. push-moraines). Both glacier forefields present a contrasting spatial configuration, making their morphodynamical evolution to differ partly from one another. The Aget push-moraine is a back-creeping GFL, which has been disconnected from the Aget glacier since the 1940s at latest. For the last two decades, surface displacement velocities have decelerated in comparison to the accelerating regional trend (PERMOS, 2019). Additionally, a 30% decrease of the electrical resistivity of the frozen ground, combined with locally observed thaw-induced subsidence of up to 10 cm/year suggest an advanced permafrost degradation. The Ritord/Challand system presents a push-moraine disconnected from its glacier as well as several push-moraines connected to a still existing debris-covered glacier. Between 2016 and 2019, surface lowering up to 10 m attesting massive ice melt has been locally detected in the former where buried glacier ice was visually observed. Whereas in the latter, subtle surface displacements ranging from 10 to 30 cm/year occur. This confirms the heterogeneity of the morphodynamical processes occurring in GFL, expressed as a function of both their spatial configuration and ground ice properties.</p><p> </p><p>Barboux, C., Delaloye R. and Lambiel, C. (2014). Inventorying slope movements in an Alpine environment using DInSAR. Earth Surface Processes and Landforms, 39/15, 2087-2099.</p><p>PERMOS 2019. Permafrost in Switzerland 2014/2015 to 2017/2018. Noetzli, J., Pellet, C., and Staub, B. (eds.), Glaciological Report (Permafrost) No. 16-19 of the Cryospheric Commission of the Swiss Academy of Sciences, 104.</p>

U.S. Mussel Watch Data from 1986 to 1994:  Temporal Trend Detection at Large Spatial Scales

1997 ◽  
Vol 31 (5) ◽  
pp. 1411-1415 ◽  
Author(s):  
B. Beliaeff ◽  
Thomas P. O'Connor ◽  
D. K. Daskalakis ◽  
P. J. Smith
Keyword(s):  
Temporal Trend ◽  
Spatial Scales ◽  
Trend Detection ◽  
Mussel Watch

scholarly journals Climatic Change in a High-Altitude Alpine Area Suggested by the Isotopic Composition Of Cold Basal Glacier Ice

1990 ◽  
Vol 14 ◽  
pp. 168-171 ◽  
Author(s):  
R. Lorrain ◽  
W. Haeberli
Keyword(s):  
Isotopic Composition ◽  
High Altitude ◽  
Temperature Effect ◽  
Climatic Change ◽  
Swiss Alps ◽  
Value Differences ◽  
Water Percolation ◽  
Melt Water ◽  
Glacier Ice ◽  
First Time

For the first time, a cold ice cover of a summit in the central Swiss Alps has been sampled from the surface to the bed for determining its isotopic composition in δD and δ18O. Results of the analyses show a striking decrease of δ-values with depth. The δ-value differences are greater than those explicable by a direct temperature effect, but a substantial increase in melt water percolation through the firn since the formation of the deepest ice layer may explain the situation of this high-altitude ice.

scholarly journals Toward a transdisciplinary understanding and a global control of emerging infectious diseases

2011 ◽  
Vol 5 (12) ◽  
pp. 903-905 ◽  
Author(s):  
Jean-Paul Gonzalez ◽  
Gérard Lambert ◽  
Anaïs Legand ◽  
Patrice Debré
Keyword(s):  
Social Sciences ◽  
Infectious Diseases ◽  
Animal Health ◽  
Emerging Infectious Diseases ◽  
Public Health Professionals ◽  
Human And Social Sciences ◽  
High Level ◽  
International Experts ◽  
Near Future ◽  
Scientific Debates

The Franceville International Centre for Medical Research (CIRMF) organized a first international symposium on infectious diseases, environments, and biodiversity. Over 200 international experts gathered in Gabon to forecast and work to prevent the emergence of infectious diseases. This symposium aimed to strengthen the regional and international fight against the emergence of infectious diseases with high-level scientific debates. Toward this goal, it brought together experts in human and animal health, the environment, and ecology, including biologists, climatologists, microbiologists, epidemiologists, public health professionals, and human and social sciences specialists. National, regional and international participants were present to debate on the challenges related to the emergence of infectious diseases and on the responses to be implemented. The symposium was very successful, and plans for a second symposium of this kind to be held in the near future in another high-biodiversity area are already underway.

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