scholarly journals Avalanches and micrometeorology driving mass and energy balance of the lowest perennial ice field of the Alps: a case study

2018 ◽  
Author(s):  
Rebecca Mott ◽  
Andreas Wolf ◽  
Maximilian Kehl ◽  
Harald Kunstmann ◽  
Michael Warscher ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Energy Balance ◽  
Mass Balance ◽  
Snow Accumulation ◽  
Near Surface ◽  
Rock Face ◽  
Katabatic Flows ◽  
Ice Field ◽  
The Alps ◽  
Perennial Ice

Abstract. The mass balance of very small glaciers is often governed either by anomalous snow accumulation, winter precipitation being multiplied by snow redistribution processes (gravitationally or wind-driven), or by suppressed snow ablation driven by micrometeorological effects lowering net radiation and/or turbulent heat exchange. In this case study, we analysed the relative contribution of snow accumulation and ablation processes governing the long- and short-term mass balance of the lowest perennial ice field of the Alps, the Ice Chapel, located at 870 m ASL in the Berchtesgaden National Park (Germany). This study emphasizes the importance of the local topographic setting for the survival of a perennial ice field located far below the climatic snow line. Although long-term mass balance measurements of the ice field surface showed a dramatic mass loss between 1973 and 2014, the ice field mass balance was rather stable between 2014 and 2017 and even showed a strong mass gain in 2017/2018 with an increase in surface height by 50–100 % relative to the ice field thickness. Measurements suggest that the winter mass balance clearly dominated the annual mass balance with 3000 % of winter snow accumulation compared to a near-by flat field station. At the Ice Chapel surface, 92 % of snow accumulation was gained by snow avalanching, thus clearly governing the 2017/2018 winter mass balance of the ice field with mean snow depths of 32 m at the end of the accumulation period. Avalanche deposition was amplified by preferential deposition of snowfall in the wind-sheltered rock face surrounding the ice field. Detailed micrometeorological measurements combined with a numerical analysis of the small-scale near-surface atmospheric flow field identified the micrometeorological processes driving the energy balance of the ice field. Measurements revealed a katabatic flow system draining down the ice field throughout the day, showing strong temporal and spatial dynamics. The spatial origin of the onset of the thermal flow system, was shown to be of particular importance for the ice field surface energy balance. Deep katabatic flows, that developed at higher-elevated shaded areas of the rock face and drained down the ice field appeared to enhance sensible heat exchange towards the ice field surface by enhancing turbulence close to the ice surface. Contrary, the shallow katabatic flow developing at the ice field surface appeared to laterally decouple the local near-surface atmosphere from the warmer adjacent air supressing heat exchange. Results thus suggest that shallow katabatic flows driven by the cooling effect of the ice field surface are especially efficient in lowering the climatic sensitivity of the ice field to the surrounding rising air temperatures. Such micrometeorological phenomena must be taken into account when calculating mass and energy balances of very small glaciers or perennial ice fields at elevations far below the climatic snow line.

scholarly journals Avalanches and micrometeorology driving mass and energy balance of the lowest perennial ice field of the Alps: a case study

2019 ◽  
Vol 13 (4) ◽  
pp. 1247-1265 ◽  
Author(s):  
Rebecca Mott ◽  
Andreas Wolf ◽  
Maximilian Kehl ◽  
Harald Kunstmann ◽  
Michael Warscher ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Energy Balance ◽  
Mass Balance ◽  
Snow Accumulation ◽  
Near Surface ◽  
Rock Face ◽  
Katabatic Flows ◽  
Ice Field ◽  
The Alps ◽  
Perennial Ice

Abstract. The mass balance of very small glaciers is often governed by anomalous snow accumulation, winter precipitation being multiplied by snow redistribution processes (gravitationally or wind driven), or suppressed snow ablation driven by micrometeorological effects lowering net radiation and/or turbulent heat exchange. In this case study, we analysed the relative contribution of snow accumulation and ablation processes governing the long- and short-term mass balance of the lowest perennial ice field of the Alps, the Ice Chapel, located at 870 m a.s.l. in the Berchtesgaden National Park (Germany). This study emphasizes the importance of the local topographic setting for the survival of a perennial ice field located far below the climatic snow line. Although long-term mass balance measurements of the ice field surface showed a dramatic mass loss between 1973 and 2014, the ice field mass balance was rather stable between 2014 and 2017 and even showed a strong mass gain in 2017/2018 with an increase in surface height by 50 %–100 % relative to the ice field thickness. Measurements suggest that the winter mass balance clearly dominated the annual mass balance. At the Ice Chapel surface, 92 % of snow accumulation was gained by snow avalanching, thus clearly governing the 2017/2018 winter mass balance of the ice field with mean snow depths of 32 m at the end of the accumulation period. Avalanche deposition was amplified by preferential deposition of snowfall in the wind-sheltered rock face surrounding the ice field. Detailed micrometeorological measurements combined with a numerical analysis of the small-scale near-surface atmospheric flow field identified the micrometeorological processes driving the energy balance of the ice field. Measurements revealed a katabatic flow system draining down the ice field throughout the day, showing strong temporal and spatial dynamics. The spatial origin of the thermal flow system was shown to be of particular importance for the ice field surface energy balance. Numerical simulation indicates that deep katabatic flows, which developed at higher-elevation shaded areas of the rock face and drained down the ice field, enhance sensible heat exchange towards the ice field surface by enhancing turbulence close to the ice surface. Conversely, the shallow katabatic flow developing at the ice field surface appeared to laterally decouple the local near-surface atmosphere from the warmer adjacent air suppressing heat exchange. Numerical results thus suggest that shallow katabatic flows driven by the cooling effect of the ice field surface are especially efficient in lowering the climatic sensitivity of the ice field to the surrounding rising air temperatures. Such micrometeorological phenomena must be taken into account when calculating mass and energy balances of very small glaciers or perennial ice fields at elevations far below the climatic snow line.

scholarly journals Snow accumulation and ice flow at Dôme du Goûter (4300 m), Mont Blanc, French Alps

1997 ◽  
Vol 43 (145) ◽  
pp. 513-521 ◽  
Author(s):  
C. Vincent ◽  
M. Vallon ◽  
J. F. Pinglot ◽  
M. Funk ◽  
L. Reynaud
Keyword(s):  
Mass Balance ◽  
Flow Model ◽  
Snow Accumulation ◽  
Ice Age ◽  
Seasonal Patterns ◽  
Ice Flow ◽  
The Alps ◽  
Radioactivity Measurements ◽  
Simple Flow

AbstractGlaciological experiments have been carried out at Dôme du Goûter (4300 m a.s.l.), Mont Blanc, in order to understand the flow of firn/ice in this high-altitude Alpine glacierized area. Accumulation measurements from stakes show a very strong spatial variability and an unusual feature of mass-balance fluctuations for the Alps, i.e. the snow accumulation does not show any seasonal patterns. Measured vertical velocities which should match with long-term mean mass balance are consistent with observed accumulations. Therefore, the measurement of vertical velocities seems a good way of quickly obtaining reliable mean accumulation values for several decades in such a region.A simple flow model can be used to determine the main flowlines of the glacier and to propose snow/ice age of core samples from the two boreholes drilled down tο the bedrock in June 1994. These results coincide with radioactivity measurements made to identify the well-known radioactive snow layers of 1963 and 1986. We can hope to obtain ice samples 55–60 years old about 20 or 30 m above the bedrock (110 m deep). Below, the deformation of the ice layers is loo great to be dated accurately.

scholarly journals Micrometeorological conditions and surface mass and energy fluxes on Lewis Glacier, Mt Kenya, in relation to other tropical glaciers

2013 ◽  
Vol 7 (4) ◽  
pp. 1205-1225 ◽  
Author(s):  
L. I. Nicholson ◽  
R. Prinz ◽  
T. Mölg ◽  
G. Kaser
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Cloud Cover ◽  
Meteorological Data ◽  
Snow Accumulation ◽  
Energy Fluxes ◽  
Glacier Surface ◽  
Monte Carlo Optimization ◽  
Surface Mass ◽  
Tropical Glaciers

Abstract. The Lewis Glacier on Mt Kenya is one of the best-studied tropical glaciers, but full understanding of the interaction of the glacier mass balance and its climatic drivers has been hampered by a lack of long-term meteorological data. Here we present 2.5 yr of meteorological data collected from the glacier surface from October 2009 to February 2012. The location of measurements is in the upper portion of Lewis Glacier, but this location experiences negative annual mass balance, and the conditions are comparable to those experienced in the lower ablation zones of South American glaciers in the inner tropics. In the context of other glaciated mountains of equatorial East Africa, the summit zone of Mt Kenya shows strong diurnal cycles of convective cloud development as opposed to the Rwenzoris, where cloud cover persists throughout the diurnal cycle, and Kilimanjaro, where clear skies prevail. Surface energy fluxes were calculated for the meteorological station site using a physical mass- and energy-balance model driven by measured meteorological data and additional input parameters that were determined by Monte Carlo optimization. Sublimation rate was lower than those reported on other tropical glaciers, and melt rate was high throughout the year, with the glacier surface reaching the melting point on an almost daily basis. Surface mass balance is influenced by both solid precipitation and air temperature, with radiation providing the greatest net source of energy to the surface. Cloud cover typically reduces the net radiation balance compared to clear-sky conditions, and thus the frequent formation of convective clouds over the summit of Mt Kenya and the associated higher rate of snow accumulation are important in limiting the rate of mass loss from the glacier surface. The analyses shown here form the basis for future glacier-wide mass and energy balance modeling to determine the climate proxy offered by the glaciers of Mt Kenya.

scholarly journals Micrometeorological conditions and surface mass and energy fluxes on Lewis glacier, Mt Kenya, in relation to other tropical glaciers

2012 ◽  
Vol 6 (6) ◽  
pp. 5181-5224 ◽  
Author(s):  
L. Nicholson ◽  
R. Prinz ◽  
T. Mölg ◽  
G. Kaser
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Cloud Cover ◽  
Meteorological Data ◽  
Snow Accumulation ◽  
Energy Fluxes ◽  
Glacier Surface ◽  
Monte Carlo Optimization ◽  
Surface Mass ◽  
Tropical Glaciers

Abstract. The Lewis Glacier on Mt Kenya is one of the best-studied tropical glaciers, but full understanding of the interaction of the glacier mass balance and climate forcing has been hampered by a lack of long term meteorological data. Here we present 2.5 yr of meteorological data collected from the glacier surface from October 2009–February 2012, which indicate that mean meteorological conditions in the upper zone of Lewis Glacier are comparable to those experienced in the ablation zones of South American tropical glaciers. In the context of other glaciated mountains of equatorial east Africa, the summit zone of Mt Kenya shows strong diurnal cycles of convective cloud development as opposed to the Rwenzoris where cloud cover persists throughout the diurnal cycle and Kilimanjaro where clear skies prevail. Surface energy fluxes were calculated for the meteorological station site using a physical mass- and energy-balance model driven by hourly measured meteorological data and additional input parameters that were determined by Monte Carlo optimization. Sublimation rate was lower than those reported on other tropical glaciers and melt rate was high throughout the year, with the glacier surface reaching the melting point on an almost daily basis. Surface mass balance is influenced by both solid precipitation and air temperature, with radiation providing the greatest net source of energy to the surface. Cloud cover typically reduces the net radiation balance compared to clear sky conditions, and thus the more frequent formation of convective clouds over the summit of Mt Kenya, and the associated higher rate of snow accumulation are important in limiting the rate of mass loss from the glacier surface. The analyses shown here are the basis for glacier-wide mass and energy balance modeling to determine the climate proxy offered by the glaciers of Mt Kenya.

Detailed simulations of snow properties and accumulation across the Antarctic Ice Sheet

2020 ◽  
Author(s):  
Jan Lenaerts ◽  
Eric Keenan ◽  
Nander Wever ◽  
Marissa Dattler ◽  
Carleen Reijmer ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Snow Accumulation ◽  
Small Scale ◽  
Blowing Snow ◽  
Antarctic Ice Sheet ◽  
Near Surface ◽  
Surface Mass ◽  
Order Of Magnitude ◽  
Snow Model

<p>Surface mass balance (SMB) represents a large uncertainty in characterizing Antarctic Ice Sheet (AIS) mass balance. Atmospheric reanalysis products, which are commonly used for AIS SMB studies, do not include small-scale snow redistribution processes even though these can be of the same order of magnitude as snow accumulation in many parts of the AIS. Therefore, a proper representation of these processes is critical to interpret local SMB and firn observations, such as from ICESat-2 repeat altimetry. In this study, we use a detailed, multi-layer snow model (SNOWPACK) forced by a global atmospheric reanalysis (MERRA-2). Firstly, we show that a new accumulation scheme, designed to better represent wind-driven snow compaction in SNOWPACK, substantially reduces simulated biases in near-surface snow density at 131 locations across the AIS. Next, we employ a distributed version of SNOWPACK to two regions on the AIS, and compare the simulation output to airborne radar and in-situ observations of SMB. Our results demonstrate that SNOWPACK can capture the timing of blowing snow events, snow erosion events, as well as observed kilometer-scale spatial SMB variability. This study illustrates the importance of using high-resolution SMB models when converting surface height (volume) observations to mass changes.</p>

scholarly journals The influence of superimposed-ice formation on the sensitivity of glacier mass balance to climate change

1997 ◽  
Vol 24 ◽  
pp. 186-190 ◽  
Author(s):  
John Woodward ◽  
Martin Sharp ◽  
Anthony Arendt
Keyword(s):  
Mass Balance ◽  
Air Temperature ◽  
High Arctic ◽  
Snow Accumulation ◽  
Ice Formation ◽  
Mean Annual Temperature ◽  
Glacier Mass Balance ◽  
Specific Mass ◽  
Near Surface ◽  
Mean Annual Air Temperature

The formation of superimposed ice at the surface of high-Arctic glaciers is an important control on glacier mass balance, but one which is usually modelled in only a schematic fashion. A method is developed to predict the relationship between the thickness of superimposed ice formed and the mean annual air temperature (which approximates the ice temperature at 14 m depth). This relationship is used to investigate the dependence of the proportion of snowpack water equivalent which forms superimposed ice on changes in mean annual temperature and patterns of snow accumulation. Increased temperatures are likely to reduce the extent of the zone of superimposed-ice accumulation and the thickness of superimposed ice formed. This will have a negative effect on glacier mass balance. This is true even if warming occurs only in the winter months, since near-surface ice temperatures will respond to such warming. For John Evans Glacier, Ellesmere Island, Nunavut, Canada (79°40’ N, 74°00’ W), a 1°C rise in mean annual air temperature due solely to winter warming is predicted to reduce the specific mass balance of the glacier by 0.008 m a–1 as a result of decreased superimposed-ice formation. Although such a response is small in comparison to the changes which might result from summer warming, it is nonetheless significant given the very low specific mass balance of many high-Arctic glaciers.

scholarly journals Snow accumulation and ice flow at Dôme du Goûter (4300 m), Mont Blanc, French Alps

1997 ◽  
Vol 43 (145) ◽  
pp. 513-521 ◽  
Author(s):  
C. Vincent ◽  
M. Vallon ◽  
J. F. Pinglot ◽  
M. Funk ◽  
L. Reynaud
Keyword(s):  
Mass Balance ◽  
Flow Model ◽  
Snow Accumulation ◽  
Ice Age ◽  
Seasonal Patterns ◽  
Ice Flow ◽  
The Alps ◽  
Radioactivity Measurements ◽  
Simple Flow

AbstractGlaciological experiments have been carried out at Dôme du Goûter (4300 m a.s.l.), Mont Blanc, in order to understand the flow of firn/ice in this high-altitude Alpine glacierized area. Accumulation measurements from stakes show a very strong spatial variability and an unusual feature of mass-balance fluctuations for the Alps, i.e. the snow accumulation does not show any seasonal patterns. Measured vertical velocities which should match with long-term mean mass balance are consistent with observed accumulations. Therefore, the measurement of vertical velocities seems a good way of quickly obtaining reliable mean accumulation values for several decades in such a region.A simple flow model can be used to determine the main flowlines of the glacier and to propose snow/ice age of core samples from the two boreholes drilled down tο the bedrock in June 1994. These results coincide with radioactivity measurements made to identify the well-known radioactive snow layers of 1963 and 1986. We can hope to obtain ice samples 55–60 years old about 20 or 30 m above the bedrock (110 m deep). Below, the deformation of the ice layers is loo great to be dated accurately.

scholarly journals The influence of superimposed-ice formation on the sensitivity of glacier mass balance to climate change

1997 ◽  
Vol 24 ◽  
pp. 186-190 ◽  
Author(s):  
John Woodward ◽  
Martin Sharp ◽  
Anthony Arendt
Keyword(s):  
Mass Balance ◽  
Air Temperature ◽  
High Arctic ◽  
Snow Accumulation ◽  
Ice Formation ◽  
Mean Annual Temperature ◽  
Glacier Mass Balance ◽  
Specific Mass ◽  
Near Surface ◽  
Mean Annual Air Temperature

The formation of superimposed ice at the surface of high-Arctic glaciers is an important control on glacier mass balance, but one which is usually modelled in only a schematic fashion. A method is developed to predict the relationship between the thickness of superimposed ice formed and the mean annual air temperature (which approximates the ice temperature at 14 m depth). This relationship is used to investigate the dependence of the proportion of snowpack water equivalent which forms superimposed ice on changes in mean annual temperature and patterns of snow accumulation.Increased temperatures are likely to reduce the extent of the zone of superimposed-ice accumulation and the thickness of superimposed ice formed. This will have a negative effect on glacier mass balance. This is true even if warming occurs only in the winter months, since near-surface ice temperatures will respond to such warming. For John Evans Glacier, Ellesmere Island, Nunavut, Canada (79°40’ N, 74°00’ W), a 1°C rise in mean annual air temperature due solely to winter warming is predicted to reduce the specific mass balance of the glacier by 0.008 m a–1 as a result of decreased superimposed-ice formation. Although such a response is small in comparison to the changes which might result from summer warming, it is nonetheless significant given the very low specific mass balance of many high-Arctic glaciers.

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