The Experts below are selected from a list of 2364 Experts worldwide ranked by ideXlab platform
Kerstin Stahl - One of the best experts on this subject based on the ideXlab platform.
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The role of Glacier Dynamics and threshold definition in the characterisation of future streamflow droughts in Glacierised catchments
2017Co-Authors: Marit Van Tiel, Marc J. P. Vis, Kerstin Stahl, Adriaan J. Teuling, Niko Wanders, Anne F. Van LoonAbstract:Abstract. Glaciers are essential hydrological reservoirs, storing and releasing water at various time scales. Short-term variability in Glacier melt is one of the causes of streamflow droughts, defined as below normal water availabilities. Streamflow droughts in Glacierised catchments have a wide range of interlinked causing factors related to precipitation and temperature on short and long time scales. Climate change affects Glacier storage capacity, with resulting consequences for discharge regimes and drought. Future projections of streamflow drought in Glacierised basins can, however, strongly depend on the modelling strategies and analysis approaches applied. Here, we examine the effect of different approaches, concerning the Glacier modelling and the drought threshold, on the characterisation of streamflow droughts in Glacierised catchments. Streamflow is simulated with the HBV-light model for two case study catchments, the Nigardsbreen catchment in Norway and the Wolverine catchment in Alaska, and two future climate change scenarios (RCP4.5 and RCP8.5). Two types of Glacier modelling are applied, a constant and dynamical Glacier area conceptualisation. Streamflow droughts are identified with the variable threshold level method and their characteristics are compared between two periods, a historical (1975–2004) and future (2071–2100) period. Two existing threshold approaches to define future droughts are employed, (1) the threshold from the historical period and (2) a transient threshold approach, whereby the threshold adapts every year in the future to the changing regimes. Results show that drought characteristics differ among the combinations of Glacier area modelling and thresholds. The historical threshold combined with a dynamical Glacier area projects extreme increases in drought severity in the future, caused by the regime shift due to a reduction in Glacier area. The historical threshold combined with a constant Glacier area results in a drastic decrease of the number of droughts. The drought characteristics between future and historic periods are more similar when the transient threshold is used, for both Glacier Dynamics conceptualisations. With the transient threshold causing factors of future droughts, can be analysed. This study revealed the different effects of methodological choices on future streamflow drought projections and it highlights how the options can be used to analyse different aspects of future droughts: the transient threshold for analysing future drought processes, the historical threshold to assess changes between periods, the constant Glacier area to analyse the effect of short term climate variability on droughts and the dynamical Glacier area to model realistic future discharges under climate change.
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Technical Note: Representing Glacier Dynamics in a semi-distributed hydrological model
Hydrology and Earth System Sciences Discussions, 2017Co-Authors: Jan Seibert, Marc J. P. Vis, Irene Kohn, Markus Weiler, Kerstin StahlAbstract:Glaciers play an important role in high-mountain hydrology. While changing Glacier areas are considered of highest importance for the understanding of future changes in runoff, Glaciers are often only poorly represented in hydrological models. Most importantly, the direct coupling between the simulated Glacier mass balances and changing Glacier areas needs feasible solutions. The use of a complex Glacier model is often not possible due to data and computational limitations. The Δ h -parameterization is a simple approach to consider the spatial variation of Glacier thickness and area changes. Here, we describe a conceptual implementation of the Δ h -parameterization into the semi-distributed hydrological model HBV-light, which also allows for the representation of Glacier advance phases, and comparison between the different versions of the implementation. The coupled glacio-hydrological simulation approach, which could also be implemented in many other semi-distributed hydrological models, is illustrated based on an example application.
Gwenn E. Flowers - One of the best experts on this subject based on the ideXlab platform.
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Correlations of suspended sediment size with bedrock lithology and Glacier Dynamics
Annals of Glaciology, 2016Co-Authors: Jeff W. Crompton, Gwenn E. FlowersAbstract:The hypothesized link between Glacier surging and bedrock geology motivates this study of the suspended sediment size distributions (SSSD) from surge-type and non-surge-type Glaciers. We analyze SSSDs from proglacial streams in 20 individual basins comprising various fractions of metasedimentary (MS) and felsic plutonic rocks. We compare the size distributions by performing tests of significance on the distribution statistics, and a principal component analysis on discrete grain sizes. We find that surge-type and non-surge-type Glaciers underlain solely by MS rocks have significantly different SSSDs, while surge-type Glaciers as a whole have remarkably similar SSSDs, regardless of the underlying bedrock geology. These observations hint at a relationship between sediment characteristics and Glacier surging, though causation in either direction cannot be established without additional data.
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A numerical study of hydrologically driven Glacier Dynamics and subglacial flooding
Proceedings of the Royal Society A: Mathematical Physical and Engineering Sciences, 2010Co-Authors: S. Pimentel, Gwenn E. FlowersAbstract:A hydrologically coupled flowband model of ‘higher order’ ice Dynamics is used to explore perturbations in response to supraglacial water drainage and subglacial flooding. The subglacial drainage system includes interacting ‘fast’ and ‘slow’ drainage elements. The fast drainage system is assumed to be composed of ice-walled conduits and the slow system of a macroporous water sheet. Under high subglacial water pressures, flexure of the overlying ice is modelled using elastic beam theory. A regularized Coulomb friction law describes basal boundary conditions that enable hydrologically driven acceleration. We demonstrate the modelled interactions between hydrology and ice Dynamics by means of three observationally inspired examples: (i) simulations of meltwater drainage at an Alpine-type Glacier produce seasonal and diurnal variability, and exhibit drainage evolution characteristic of the so-called ‘spring transition’; (ii) horizontal and vertical diurnal accelerations are modelled in response to summer meltwater input at a Greenland-type outlet Glacier; and (iii) short-lived perturbations to basal water pressure and ice-flow speed are modelled in response to the prescribed drainage of a supraglacial lake. Our model supports the suggestion that a channelized drainage system can form beneath the margins of the Greenland ice sheet, and may contribute to reducing the dynamic impact of floods derived from supraglacial lakes.
Jan Seibert - One of the best experts on this subject based on the ideXlab platform.
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Technical Note: Representing Glacier Dynamics in a semi-distributed hydrological model
Hydrology and Earth System Sciences Discussions, 2017Co-Authors: Jan Seibert, Marc J. P. Vis, Irene Kohn, Markus Weiler, Kerstin StahlAbstract:Glaciers play an important role in high-mountain hydrology. While changing Glacier areas are considered of highest importance for the understanding of future changes in runoff, Glaciers are often only poorly represented in hydrological models. Most importantly, the direct coupling between the simulated Glacier mass balances and changing Glacier areas needs feasible solutions. The use of a complex Glacier model is often not possible due to data and computational limitations. The Δ h -parameterization is a simple approach to consider the spatial variation of Glacier thickness and area changes. Here, we describe a conceptual implementation of the Δ h -parameterization into the semi-distributed hydrological model HBV-light, which also allows for the representation of Glacier advance phases, and comparison between the different versions of the implementation. The coupled glacio-hydrological simulation approach, which could also be implemented in many other semi-distributed hydrological models, is illustrated based on an example application.
J. Weiss - One of the best experts on this subject based on the ideXlab platform.
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Modelling the impact of submarine frontal melting and ice mélange on Glacier Dynamics
The Cryosphere, 2015Co-Authors: J. Krug, G. Durand, O. Gagliardini, J. WeissAbstract:Abstract. Submarine melting of the calving face of tidewater Glaciers and the mechanical back force applied by the ice melange layer are two mechanisms generally proposed to explain seasonal variations at the calving front of tidewater Glaciers. However, the way these processes affect the calving rate and Glacier Dynamics remains uncertain. In this study, we used a finite element-based model that solves the full Stokes equations to simulate the impact of these forcings on two-dimensional theoretical flow line Glacier configurations. The model, which includes calving processes, suggests that frontal melting affects the position of the terminus only slightly (less than a few hundred metres) and does not affect the multiannual Glacier mass balance at all. However, the ice melange has a greater impact on the advance and retreat cycles of the Glacier front (more than several kilometres) and its consequences for the mass balance are not completely negligible, stressing the need for better characterization of forcing properties. We also show that ice melange forcing against the calving face can mechanically prevent crevasse propagation at sea level and hence prevent calving. Results also reveal different behaviours in grounded and floating Glaciers: in the case of a floating extension, the strongest forcings can disrupt the Glacier equilibrium by modifying its buttressing and ice flux at the grounding line.
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Modelling the impact of submarine frontal melting and ice mélange on Glacier Dynamics
The Cryosphere, 2015Co-Authors: J. Krug, G. Durand, O. Gagliardini, J. WeissAbstract:Submarine melting of the calving face of tidewa-ter Glaciers and the mechanical back force applied by the ice mélange layer are two mechanisms generally proposed to explain seasonal variations at the calving front of tide-water Glaciers. However, the way these processes affect the calving rate and Glacier Dynamics remains uncertain. In this study, we used a finite element-based model that solves the full Stokes equations to simulate the impact of these forcings on two-dimensional theoretical flow line Glacier configurations. The model, which includes calving processes, suggests that frontal melting affects the position of the terminus only slightly (less than a few hundred metres) and does not affect the multiannual Glacier mass balance at all. However, the ice mélange has a greater impact on the advance and retreat cycles of the Glacier front (more than several kilometres) and its consequences for the mass balance are not completely negligible , stressing the need for better characterization of forcing properties. We also show that ice mélange forcing against the calving face can mechanically prevent crevasse propagation at sea level and hence prevent calving. Results also reveal different behaviours in grounded and floating Glaciers: in the case of a floating extension, the strongest forcings can disrupt the Glacier equilibrium by modifying its buttressing and ice flux at the grounding line.
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Modelling the impact of submarine frontal melting and ice mélange on Glacier Dynamics
2015Co-Authors: J. Krug, G. Durand, O. Gagliardini, J. WeissAbstract:Abstract. Two mechanisms are generally proposed to explain seasonal variations in the calving front of tidewater Glaciers: submarine melting of the calving face and the mechanical back-force applied by the ice mélange. However, the way these processes affect the calving rate and the Glacier Dynamics remains uncertain. In this study, we used the finite element model Elmer/Ice to simulate the impact of these forcings on more than 200 two dimensional theoretical flowline Glacier configurations. The model, which includes calving processes, suggests that frontal melting affects the position of the terminus only slightly (< a few hundred meters) and does not affect the pluriannual Glacier mass balance at all. However, the ice mélange has a greater impact on the advance and retreat cycles of the Glacier front (more than several 1000 m) and its consequences for the mass balance are not completely negligible, stressing the need for better characterization of forcing properties. We also show that ice mélange forcing against the calving face can mechanically prevent crevasse propagation at sea level and hence prevent calving. Results also revealed different behaviors in grounded and floating Glaciers: in the case of a floating extension, the heaviest forcings can disrupt the Glacier equilibrium by modifying its buttressing and ice flux at the grounding line.
Andrew J. Russell - One of the best experts on this subject based on the ideXlab platform.
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Response of Glacier flow and structure to proglacial lake development and climate at Fjallsjökull, south-east Iceland
Journal of Glaciology, 2019Co-Authors: Rebecca Dell, Rachel Carr, Emrys Phillips, Andrew J. RussellAbstract:Over recent decades, the number of outlet Glaciers terminating in lakes in Iceland has increased in line with climate warming. The mass-balance changes of these lake-terminating outlet Glaciers are sensitive to rising air temperatures, due to altered Glacier Dynamics and increased surface melt. This study aims to better understand the relationship between proglacial lake development, climate, Glacier Dynamics and Glacier structure at Fjallsjokull, a large, lake-terminating outlet Glacier in south-east Iceland. We used satellite imagery to map Glacier terminus position and lake extent between 1973 and 2016, and a combination of aerial and satellite imagery to map the structural architecture of the Glacier's terminus in 1982, 1994 and 2011. The temporal evolution of ice surface velocities between 1990 and 2018 was calculated using feature tracking. Statistically significant increases in the rate of terminus retreat and lake expansion were identified in 2001, 2009 and 2011. Our surface velocity and structural datasets revealed the development of localised flow ‘corridors’ over time, which conveyed relatively faster flow towards the Glacier's terminus. We attribute the overall changes in Dynamics and structural architecture at Fjallsjokull to rising air temperatures, but argue that the spatial complexities are driven by Glacier specific factors, such as basal topography.
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Interactions between Glacier Dynamics, ice structure, and climate at Fjallsjökul, south-east Iceland
2019Co-Authors: Rebecca Dell, Rachel Carr, Emrys Phillips, Andrew J. RussellAbstract:Over recent decades, the number of outlet Glaciers terminating in lakes in Iceland has increased in line with climate warming. The mass-balance changes of these lake-terminating outlet gla-ciers are sensitive to rising air temperatures, due to altered Glacier Dynamics and increased surface melt. This study aims to better understand the relationship between proglacial lake development, climate, Glacier Dynamics and Glacier structure at Fjallsjokull, a large, lake-terminating outlet Glacier in south-east Iceland. We used satellite imagery to map Glacier terminus position and lake extent between 1973 and 2016, and a combination of aerial and satellite imagery to map the structural architecture of the Glacier’s terminus in 1982, 1994 and 2011. The temporal evolution of ice surface velocities between 1990 and 2018 was calculated using feature tracking. Statistically significant increases in the rate of terminus retreat and lake expansion were identified in 2001, 2009 and 2011. Our surface velocity and structural datasets revealed the development of localised flow ‘corridors’ over time, which conveyed relatively faster flow towards the Glacier’s terminus. We attribute the overall changes in Dynamics and structural architecture at Fjallsjokull to rising air temperatures, but argue that the spatial complexities are driven by Glacier specific factors, such as basal topography.