scholarly journals Ice flow velocity as a sensitive indicator of glacier state

2018 ◽  
Author(s):  
Martin Stocker-Waldhuber ◽  
Andrea Fischer ◽  
Kay Helfricht ◽  
Michael Kuhn
Keyword(s):  
Flow Dynamics ◽  
Sensitive Indicator ◽  
Interannual Variations ◽  
Climatic Forcing ◽  
Velocity Change ◽  
Ice Flow ◽  
Glacier Length ◽  
Length Changes ◽  
Flow Velocities

Abstract. Climatic forcing affects glacier length changes, mass balance and ice flow dynamics on different time scales and also dependent on topography. The first two of these parameters are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics exist with the potential to serve as long-term indicators of glacier response to climate change. With more than 100 years of measurements of ice flow velocities at stakes and stone lines on Hintereisferner (HEF) and more than 50 years on Kesselwandferner (KWF), records of annual velocity change are as long as records of glacier fluctuations. Interannual variations of ice flow velocities and shorter supporting interpretations of long-term records have been measured on Gepatschferner (GPF) and Taschachferner (TSF) for nearly 10 years. The ice flow velocities on Hintereisferner and especially on Kesselwandferner show great variations between advancing and retreating periods, with magnitudes increasing from the highest to the lowest stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong sign of the severe retreat of the glaciers in recent decades.

scholarly journals Long-term records of glacier surface velocities in the Ötztal Alps (Austria)

2019 ◽  
Vol 11 (2) ◽  
pp. 705-715 ◽  
Author(s):  
Martin Stocker-Waldhuber ◽  
Andrea Fischer ◽  
Kay Helfricht ◽  
Michael Kuhn
Keyword(s):  
Mass Balance ◽  
Glacier Mass Balance ◽  
Climatic Forcing ◽  
Glacier Surface ◽  
Ice Flow ◽  
Strong Indicator ◽  
Glacier Length ◽  
Length Changes ◽  
Flow Velocities

Abstract. Climatic forcing affects glacier mass balance, which causes changes in ice flow dynamics and glacier length changes on different timescales. Mass balance and length changes are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics have been recorded. Here we present a unique dataset of yearly averaged ice flow velocity measurements at stakes and stone lines covering more than 100 years on Hintereisferner and more than 50 years on Kesselwandferner. Moreover, the dataset contains sub-seasonal variations in ice flow from Gepatschferner and Taschachferner covering almost 10 years. The ice flow velocities on Hintereisferner and (especially) on Kesselwandferner show great variation between advancing and retreating periods, with magnitudes increasing from the stakes at higher elevations to the lower-elevated stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong indicator of the negative mass balances of the glaciers in recent decades. The velocity datasets of the four glaciers are available at https://doi.org/10.1594/PANGAEA.896741.

scholarly journals Long-term records of glacier surface velocities in the Ötztal Alps (Austria)

2019 ◽  
Author(s):  
Martin Stocker-Waldhuber ◽  
Andrea Fischer ◽  
Kay Helfricht ◽  
Michael Kuhn
Keyword(s):  
Mass Balance ◽  
Glacier Mass Balance ◽  
Data Sets ◽  
Climatic Forcing ◽  
Glacier Surface ◽  
Ice Flow ◽  
Strong Indicator ◽  
Length Changes ◽  
Flow Velocities

Abstract. Climatic forcing affects glacier mass balance and ice flow dynamics on different time scales, resulting in length changes. Mass Balance and length changes are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics have been recorded. With more than 100 years of measurements of ice flow velocities at stakes and stone lines on Hintereisferner and more than 50 years on Kesselwandferner, annual velocity and glacier fluctuation records have similar lengths. Subseasonal variations of ice flow velocities have been measured on Gepatschferner and Taschachferner for nearly a decade. The ice flow velocities on Hintereisferner and especially on Kesselwandferner show great variations between advancing and retreating periods, with magnitudes increasing from the highest to the lowest stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong indicator of the negative mass balances of the glaciers in recent decades. The velocity data sets of the four glaciers are available at https://doi.pangaea.de/10.1594/PANGAEA.896741.

scholarly journals Ice-flow and mass changes of Lewis Glacier, Mount Kenya, East Africa, 1986–90: observations and modeling

1992 ◽  
Vol 38 (128) ◽  
pp. 36-42
Author(s):  
Stefan Hastenrath
Keyword(s):  
Time Interval ◽  
Volume Loss ◽  
Climatic Forcing ◽  
Ice Flow ◽  
Mass Budget ◽  
Modeling And Prediction ◽  
Mass Redistribution ◽  
Glacier Changes ◽  
Flow Velocities

AbstractThe long-term monitoring of Lewis Glacier on Mount Kenya serves as a basis for the study of glacier evolution in response to climatic forcing through modeling of its ice flow and mass budget. Following up on an earlier modeling and prediction study to 1990, this paper examines the ice-mass and flow changes in relation to the net-balance conditions over 1986–90. A model experiment using as climatic forcing the observed 1978–86 vertical net-balance profile yielded a volume loss and slow down of ice flow more drastic than observed during 1986–90. The causes of this discrepancy were examined in successive model experiments. Realistic simulations of mass-budget and thickness changes over 1986–90 are obtained using as input the net-balance forcing for the same period rather than for the preceding 1978–86 interval, and approximate flow velocities. With the same net-balance forcing and a completely stagnant Lewis Glacier, the elimination of mass redistribution by ice flow acts to mitigate the loss of volume and thickness in the upper glacier, and to accentuate it in the lower glacier. Accordingly, the observed 1986–90 net-balance profile along with the 1990 ice-flow velocities provide suitable input for the modeling of Lewis Glacier changes to 1994. Under continuation of the 1986–90 climatic forcing, ice thinning ranging from less than 1 m in the upper glacier to more than 7 m in the lower glacier, and a total volume loss of order 57 × 104 m3, are anticipated over the 1990–94 time interval.

scholarly journals Ice-flow and mass changes of Lewis Glacier, Mount Kenya, East Africa, 1986–90: observations and modeling

1992 ◽  
Vol 38 (128) ◽  
pp. 36-42 ◽  
Author(s):  
Stefan Hastenrath
Keyword(s):  
Time Interval ◽  
Volume Loss ◽  
Climatic Forcing ◽  
Ice Flow ◽  
Mass Budget ◽  
Modeling And Prediction ◽  
Mass Redistribution ◽  
Glacier Changes ◽  
Flow Velocities

AbstractThe long-term monitoring of Lewis Glacier on Mount Kenya serves as a basis for the study of glacier evolution in response to climatic forcing through modeling of its ice flow and mass budget. Following up on an earlier modeling and prediction study to 1990, this paper examines the ice-mass and flow changes in relation to the net-balance conditions over 1986–90. A model experiment using as climatic forcing the observed 1978–86 vertical net-balance profile yielded a volume loss and slow down of ice flow more drastic than observed during 1986–90. The causes of this discrepancy were examined in successive model experiments. Realistic simulations of mass-budget and thickness changes over 1986–90 are obtained using as input the net-balance forcing for the same period rather than for the preceding 1978–86 interval, and approximate flow velocities. With the same net-balance forcing and a completely stagnant Lewis Glacier, the elimination of mass redistribution by ice flow acts to mitigate the loss of volume and thickness in the upper glacier, and to accentuate it in the lower glacier. Accordingly, the observed 1986–90 net-balance profile along with the 1990 ice-flow velocities provide suitable input for the modeling of Lewis Glacier changes to 1994. Under continuation of the 1986–90 climatic forcing, ice thinning ranging from less than 1 m in the upper glacier to more than 7 m in the lower glacier, and a total volume loss of order 57 × 104m3, are anticipated over the 1990–94 time interval.

scholarly journals Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

2017 ◽  
Vol 11 (1) ◽  
pp. 281-302 ◽  
Author(s):  
Henning Åkesson ◽  
Kerim H. Nisancioglu ◽  
Rianne H. Giesen ◽  
Mathieu Morlighem
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
Ice Age ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Surface Mass ◽  
Ice Caps ◽  
Ice Cap ◽  
Length Changes

Abstract. Understanding of long-term dynamics of glaciers and ice caps is vital to assess their recent and future changes, yet few long-term reconstructions using ice flow models exist. Here we present simulations of the maritime Hardangerjøkulen ice cap in Norway from the mid-Holocene through the Little Ice Age (LIA) to the present day, using a numerical ice flow model combined with glacier and climate reconstructions. In our simulation, under a linear climate forcing, we find that Hardangerjøkulen grows from ice-free conditions in the mid-Holocene to its maximum extent during the LIA in a nonlinear, spatially asynchronous fashion. During its fastest stage of growth (2300–1300 BP), the ice cap triples its volume in less than 1000 years. The modeled ice cap extent and outlet glacier length changes from the LIA until today agree well with available observations. Volume and area for Hardangerjøkulen and several of its outlet glaciers vary out-of-phase for several centuries during the Holocene. This volume–area disequilibrium varies in time and from one outlet glacier to the next, illustrating that linear relations between ice extent, volume and glacier proxy records, as generally used in paleoclimatic reconstructions, have only limited validity. We also show that the present-day ice cap is highly sensitive to surface mass balance changes and that the effect of the ice cap hypsometry on the mass balance–altitude feedback is essential to this sensitivity. A mass balance shift by +0.5 m w.e. relative to the mass balance from the last decades almost doubles ice volume, while a decrease of 0.2 m w.e. or more induces a strong mass balance–altitude feedback and makes Hardangerjøkulen disappear entirely. Furthermore, once disappeared, an additional +0.1 m w.e. relative to the present mass balance is needed to regrow the ice cap to its present-day extent. We expect that other ice caps with comparable geometry in, for example, Norway, Iceland, Patagonia and peripheral Greenland may behave similarly, making them particularly vulnerable to climate change.

scholarly journals Ice-flow velocities on Rutford Ice Stream, West Antarctica, are stable over decadal timescales

2009 ◽  
Vol 55 (190) ◽  
pp. 339-344 ◽  
Author(s):  
G.H. Gudmundsson ◽  
A. Jenkins
Keyword(s):  
Temporal Variations ◽  
Flow Speed ◽  
Seasonal Effects ◽  
West Antarctica ◽  
Ice Flow ◽  
Long Period ◽  
Ice Stream ◽  
Surface Ice ◽  
Flow Velocities

AbstractSurface ice-flow velocities measured at stakes on Rutford Ice Stream, West Antarctica, covering a period of ∼25 years are analysed for evidence of temporal variations in flow. No indications of significant long-term changes in flow are found. Earlier observations have shown significant tidally related variations in flow speed. We conclude that temporal variability on Rutford Ice Stream, West Antarctica, appears limited to tidal periods of days and weeks, and weaker interannual variation, possibly related to long-period tides or seasonal effects, while long-term (decadal) changes in flow speed are either absent or smaller than ∼0.1% a−1.

scholarly journals Overestimation and Adjustment of Antarctic Ice Flow Velocity Fields Reconstructed from Historical Satellite Imagery

2021 ◽  
Author(s):  
Rongxing Li ◽  
Yuan Cheng ◽  
Haotian Cui ◽  
Menglian Xia ◽  
Xiaohan Yuan ◽  
...  
Keyword(s):  
Satellite Image ◽  
Ice Sheet ◽  
Image Data ◽  
Ground Truth ◽  
Flow Dynamics ◽  
Landsat 8 ◽  
Sea Level Changes ◽  
Velocity Mapping ◽  
Ice Flow

Abstract. Antarctic ice velocity maps describe the ice flow dynamics of the ice sheet and are one of the primary components used to estimate the Antarctic mass balance and contribution to global sea level changes. In comparison to velocity maps covering monthly to weekly time spans derived from the images of optical imaging satellites taken in recent decades, historical maps, from before the 1990s, generally cover longer time spans, e.g., over 10 years, due to the scarce spatial and temporal coverage of earlier satellite image data. We found velocity overestimations in such long-term maps that can reach from ~69 m a−1 (7-year span) in Totten Glacier, East Antarctica, up to ~930 m a−1 (10-year span) in Pine Island, West Antarctica. We propose an innovative Lagrangian velocity-based method for overestimation correction without the use of field observations or additional image data. The method is validated by using a set of “ground truth” velocity maps for Totten Glacier which are produced from high-quality Landsat 8 images from 2013 to 2020. Subsequently, the validated method is applied to a historical velocity map of the David Glacier region from images from 1972–1989 acquired during Landsat 1, 4 and 5 satellite missions. It is demonstrated that velocity overestimations of up to 39 m a−1 for David Glacier and 69 m a−1 for Totten Glacier can be effectively corrected. Furthermore, temporal acceleration information, e.g., on calving events, is preserved in the corrected velocity maps and can be used for long-term ice flow dynamics analysis. We recommend that overestimations of more than the velocity mapping uncertainty (1σ) be corrected. This velocity overestimation correction method can be applied to the production of regional and ice sheet-wide historical velocity maps from long-term satellite images.

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

2019 ◽  
Author(s):  
David Parkes ◽  
Hugues Goosse
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Industrial History ◽  
Glacier Changes ◽  
Glacier Length ◽  
Length Changes ◽  
Almost All ◽  
Post Industrial ◽  
The Impact

Abstract. A large majority of the direct observational record for glacier changes falls within the post-industrial period, associated with global glacier retreat. Given this availability of data, and significant focus in contemporary glacier modelling falling on post-industrial retreat, glacier models are typically calibrated using – and validated with – only observations from points where glaciers were considerably out of equilibrium. In order to develop a broader picture of the skill of one glacier model in active development – the Open Global Glacier Model (OGGM) – we model glaciers for extended historical timescales of 850–2004 CE using a selection of 6 climate model outputs, including recent post-industrial history. We select glaciers for which long term glacier length observations are available, in order to compare these observations with the model results, and we find glaciers for this purpose in almost all glacierised regions globally. In many regions, the modelled glacier changes are consistent with observations, with recent retreat often as rapid as – or sometimes more rapid than – modelled retreats. We also model this set of glaciers using modified climate timeseries from each of the 6 climate models to 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. Overall, with the vast majority of glaciers successfully modelled, and recent observational trends in many regions reproduced by the model running 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, where glaciers are typically larger and experience less rapid (and less globally consistent) geometry changes.

scholarly journals Health and sustainability of glaciers in High Mountain Asia

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Evan Miles ◽  
Michael McCarthy ◽  
Amaury Dehecq ◽  
Marin Kneib ◽  
Stefan Fugger ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Field Measurements ◽  
Tien Shan ◽  
High Mountain ◽  
Specific Mass ◽  
Ice Flow ◽  
Ice Volume ◽  
Mass Redistribution ◽  
Glacier Ablation

AbstractGlaciers in High Mountain Asia generate meltwater that supports the water needs of 250 million people, but current knowledge of annual accumulation and ablation is limited to sparse field measurements biased in location and glacier size. Here, we present altitudinally-resolved specific mass balances (surface, internal, and basal combined) for 5527 glaciers in High Mountain Asia for 2000–2016, derived by correcting observed glacier thinning patterns for mass redistribution due to ice flow. We find that 41% of glaciers accumulated mass over less than 20% of their area, and only 60% ± 10% of regional annual ablation was compensated by accumulation. Even without 21st century warming, 21% ± 1% of ice volume will be lost by 2100 due to current climatic-geometric imbalance, representing a reduction in glacier ablation into rivers of 28% ± 1%. The ablation of glaciers in the Himalayas and Tien Shan was mostly unsustainable and ice volume in these regions will reduce by at least 30% by 2100. The most important and vulnerable glacier-fed river basins (Amu Darya, Indus, Syr Darya, Tarim Interior) were supplied with >50% sustainable glacier ablation but will see long-term reductions in ice mass and glacier meltwater supply regardless of the Karakoram Anomaly.

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