Ice thickness and volume of the Renland Ice Cap, East Greenland

Abstract To assess the amount of ice volume stored in glaciers or ice caps, a method to estimate ice thickness distribution is required for glaciers where no direct observations are available. In this study, we use an existing inverse method to estimate the bedrock topography and ice thickness of the Renland Ice Cap, East Greenland, using satellite-based observations of the surface topography. The inverse approach involves a procedure in which an ice dynamical model is used to build-up an ice cap in steady state with climate forcing from a regional climate model, and the bedrock is iteratively adjusted until the modelled and observed surface topography match. We validate our model results against information from airborne radar data and satellite observed surface velocity, and we find that the inferred ice thickness and thereby the stored total volume of the ice cap is sensitive to the assumed ice softness and basal slipperiness. The best basal model parameters for the Renland Ice Cap are determined and the best estimated total ice volume of 384 km3 is found. The Renland Ice Cap is particularly interesting because of its location at a high elevation plateau and hence assumed low sensitivity to climate change.

Download Full-text

Estimating the volume of glaciers in the Himalayan–Karakoram region using different methods

The Cryosphere ◽

10.5194/tc-8-2313-2014 ◽

2014 ◽

Vol 8 (6) ◽

pp. 2313-2333 ◽

Cited By ~ 104

Author(s):

H. Frey ◽

H. Machguth ◽

M. Huss ◽

C. Huggel ◽

S. Bajracharya ◽

...

Keyword(s):

Thickness Distribution ◽

Critical Evaluation ◽

Estimation Method ◽

Volume Estimation ◽

Ice Thickness ◽

Model Parameters ◽

Distribution Models ◽

Ice Volume ◽

Sensitivity Assessment ◽

Volume Estimates

Abstract. Ice volume estimates are crucial for assessing water reserves stored in glaciers. Due to its large glacier coverage, such estimates are of particular interest for the Himalayan–Karakoram (HK) region. In this study, different existing methodologies are used to estimate the ice reserves: three area–volume relations, one slope-dependent volume estimation method, and two ice-thickness distribution models are applied to a recent, detailed, and complete glacier inventory of the HK region, spanning over the period 2000–2010 and revealing an ice coverage of 40 775 km2. An uncertainty and sensitivity assessment is performed to investigate the influence of the observed glacier area and important model parameters on the resulting total ice volume. Results of the two ice-thickness distribution models are validated with local ice-thickness measurements at six glaciers. The resulting ice volumes for the entire HK region range from 2955 to 4737 km3, depending on the approach. This range is lower than most previous estimates. Results from the ice thickness distribution models and the slope-dependent thickness estimations agree well with measured local ice thicknesses. However, total volume estimates from area-related relations are larger than those from other approaches. The study provides evidence on the significant effect of the selected method on results and underlines the importance of a careful and critical evaluation.

Download Full-text

The ice thickness distribution of Flask Glacier, Antarctic Peninsula, determined by combining radio-echo soundings, surface velocity data and flow modelling

Annals of Glaciology ◽

10.3189/2013aog63a603 ◽

2013 ◽

Vol 54 (63) ◽

pp. 18-24 ◽

Cited By ~ 20

Author(s):

Daniel Farinotti ◽

Hugh Corr ◽

G.Hilmar Gudmundsson

Keyword(s):

Antarctic Peninsula ◽

Thickness Distribution ◽

Surface Velocity ◽

Ice Thickness ◽

Ice Shelf ◽

Ice Flow ◽

Ice Volume ◽

Flow Modelling ◽

Bedrock Topography ◽

Sparse Measurements

AbstractAn interpolated bedrock topography is presented for Flask Glacier, one of the tributaries of the remnant part of the Larsen B ice shelf, Antarctic Peninsula. The ice thickness distribution is derived by combining direct but sparse measurements from airborne radio-echo soundings with indirect estimates obtained from ice-flow modelling. The ice-flow model is applied to a series of transverse profiles, and a first estimate of the bedrock is iteratively adjusted until agreement between modelled and measured surface velocities is achieved. The adjusted bedrock is then used to reinterpret the radio-echo soundings, and the recovered information used to further improve the estimate of the bedrock itself. The ice flux along the glacier center line provides an additional and independent constraint on the ice thickness. The resulting bedrock topography reveals a glacier bed situated mainly below sea level with sections having retrograde slope. The total ice volume of 120 ±15 km3 for the considered area of 215 km2 corresponds to an average ice thickness of 560 ± 70 m.

Download Full-text

Combining SAR interferometry and the equation of continuity to estimate the three-dimensional glacier surface-velocity vector

Journal of Glaciology ◽

10.3189/s0022143000001398 ◽

1999 ◽

Vol 45 (151) ◽

pp. 533-538 ◽

Cited By ~ 2

Author(s):

Niels Reeh ◽

Søren Nørvang Madsen ◽

Johan Jakob Mohr

Keyword(s):

Steady State ◽

Mass Balance ◽

Vertical Velocity ◽

Velocity Vector ◽

Thickness Distribution ◽

Vertical Surface ◽

Horizontal Velocity ◽

Sar Interferometry ◽

Surface Velocity ◽

Ice Thickness

AbstractUntil now, an assumption of surface-parallel glacier flow has been used to express the vertical velocity component in terms of the horizontal velocity vector, permitting all three velocity components to be determined from synthetic aperture radar interferometry. We discuss this assumption, which neglects the influence of the local mass balance and a possible contribution to the vertical velocity arising if the glacier is not in steady state. We find that the mass-balance contribution to the vertical surface velocity is not always negligible as compared to the surface-slope contribution. Moreover, the vertical velocity contribution arising if the ice sheet is not in steady state can be significant. We apply the principle of mass conservation to derive an equation relating the vertical surface velocity to the horizontal velocity vector. This equation, valid for both steady-state and non-steady-state conditions, depends on the ice-thickness distribution. Replacing the surface-parallel-flow assumption with a correct relationship between the surface velocity components requires knowledge of additional quantities such as surface mass balance or ice thickness.

Download Full-text

Ice thickness distribution of all Swiss glaciers based on extended ground-penetrating radar data and glaciological modeling

Journal of Glaciology ◽

10.1017/jog.2021.55 ◽

2021 ◽

pp. 1-19

Author(s):

Melchior Grab ◽

Enrico Mattea ◽

Andreas Bauder ◽

Matthias Huss ◽

Lasse Rabenstein ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Thickness Distribution ◽

Radar Data ◽

Tourism Industry ◽

Swiss Alps ◽

Ice Thickness ◽

Hazard Management ◽

Bed Topography ◽

Ice Volume ◽

Ground Penetrating

Abstract Accurate knowledge of the ice thickness distribution and glacier bed topography is essential for predicting dynamic glacier changes and the future developments of downstream hydrology, which are impacting the energy sector, tourism industry and natural hazard management. Using AIR-ETH, a new helicopter-borne ground-penetrating radar (GPR) platform, we measured the ice thickness of all large and most medium-sized glaciers in the Swiss Alps during the years 2016–20. Most of these had either never or only partially been surveyed before. With this new dataset, 251 glaciers – making up 81% of the glacierized area – are now covered by GPR surveys. For obtaining a comprehensive estimate of the overall glacier ice volume, ice thickness distribution and glacier bed topography, we combined this large amount of data with two independent modeling algorithms. This resulted in new maps of the glacier bed topography with unprecedented accuracy. The total glacier volume in the Swiss Alps was determined to be 58.7 ± 2.5 km3 in the year 2016. By projecting these results based on mass-balance data, we estimated a total ice volume of 52.9 ± 2.7 km3 for the year 2020. Data and modeling results are accessible in the form of the SwissGlacierThickness-R2020 data package.

Download Full-text

Measuring and inferring the ice thickness distribution of four glaciers in the Tien Shan, Kyrgyzstan

Journal of Glaciology ◽

10.1017/jog.2020.104 ◽

2020 ◽

pp. 1-18

Author(s):

Lander Van Tricht ◽

Philippe Huybrechts ◽

Jonas Van Breedam ◽

Johannes J. Fürst ◽

Oleg Rybak ◽

...

Keyword(s):

Cross Validation ◽

Thickness Distribution ◽

Tien Shan ◽

Ice Thickness ◽

Ice Volume ◽

In Situ Data ◽

Radio Echo Sounding ◽

Thickness Measurements ◽

Tien Shan Mountains

Abstract Glaciers in the Tien Shan mountains contribute considerably to the fresh water used for irrigation, households and energy supply in the dry lowland areas of Kyrgyzstan and its neighbouring countries. To date, reconstructions of the current ice volume and ice thickness distribution remain scarce, and accurate data are largely lacking at the local scale. Here, we present a detailed ice thickness distribution of Ashu-Tor, Bordu, Golubin and Kara-Batkak glaciers derived from radio-echo sounding measurements and modelling. All the ice thickness measurements are used to calibrate three individual models to estimate the ice thickness in inaccessible areas. A cross-validation between modelled and measured ice thickness for a subset of the data is performed to attribute a weight to every model and to assemble a final composite ice thickness distribution for every glacier. Results reveal the thickest ice on Ashu-Tor glacier with values up to 201 ± 12 m. The ice thickness measurements and distributions are also compared with estimates composed without the use of in situ data. These estimates approach the total ice volume well, but local ice thicknesses vary substantially.

Download Full-text

Sea ice deformation and thickness in the Western Ross Sea

10.5194/egusphere-egu21-10607 ◽

2021 ◽

Author(s):

Wolfgang Rack ◽

Daniel Price ◽

Christian Haas ◽

Patricia J. Langhorne ◽

Greg H. Leonard

Keyword(s):

Sea Ice ◽

Satellite Images ◽

Ross Sea ◽

Thickness Distribution ◽

Ice Thickness ◽

Ice Dynamics ◽

Sea Ice Thickness ◽

Ice Volume ◽

Terra Nova Bay ◽

Western Ross Sea

Sea ice cover is arguably the longest and best observed climate variable from space, with over four decades of highly reliable daily records of extent in both hemispheres. In Antarctica, a slight positive decadal trend in sea ice cover is driven by changes in the western Ross Sea, where a variation in weather patterns over the wider region forced a change in meridional winds. The distinguishing wind driven sea ice process in the western Ross Sea is the regular occurrence of the Ross Sea, McMurdo Sound, and Terra Nova Bay polynyas. Trends in sea ice volume and mass in this area unknown, because ice thickness and dynamics are particularly hard to measure.Here we present the first comprehensive and direct assessment of large-scale sea-ice thickness distribution in the western Ross Sea. Using an airborne electromagnetic induction (AEM) ice thickness sensor towed by a fixed wing aircraft (Basler BT-67), we observed in November 2017 over a distance of 800 km significantly thicker ice than expected from thermodynamic growth alone. By means of time series of satellite images and wind data we relate the observed thickness distribution to satellite derived ice dynamics and wind data. Strong southerly winds with speeds of up to 25 ms-1 in early October deformed the pack ice, which was surveyed more than a month later.We found strongly deformed ice with a mean and maximum thickness of 2.0 and 15.6 m, respectively. Sea-ice thickness gradients are highest within 100-200 km of polynyas, where the mean thickness of the thickest 10% of ice is 7.6 m. From comparison with aerial photographs and satellite images we conclude that ice preferentially grows in deformational ridges; about 43% of the sea ice volume in the area between McMurdo Sound and Terra Nova Bay is concentrated in more than 3 m thick ridges which cover about 15% of the surveyed area. Overall, 80% of the ice was found to be heavily deformed and concentrated in ridges up to 11.8 m thick.Our observations hold a link between wind driven ice dynamics and the ice mass exported from the western Ross Sea. The sea ice statistics highlighted in this contribution forms a basis for improved satellite derived mass balance assessments and the evaluation of sea ice simulations.

Download Full-text

Combining SAR interferometry and the equation of continuity to estimate the three-dimensional glacier surface-velocity vector

Journal of Glaciology ◽

10.1017/s0022143000001398 ◽

1999 ◽

Vol 45 (151) ◽

pp. 533-538 ◽

Cited By ~ 26

Author(s):

Niels Reeh ◽

Søren Nørvang Madsen ◽

Johan Jakob Mohr

Keyword(s):

Steady State ◽

Mass Balance ◽

Vertical Velocity ◽

Velocity Vector ◽

Thickness Distribution ◽

Vertical Surface ◽

Horizontal Velocity ◽

Sar Interferometry ◽

Surface Velocity ◽

Ice Thickness

Download Full-text

On the astronomical forcing of simple conceptual ice age models

10.5194/egusphere-egu2020-10137 ◽

2020 ◽

Author(s):

Gaëlle Leloup ◽

Didier Paillard

Keyword(s):

Conceptual Model ◽

Climate Model ◽

Ice Age ◽

Early Pleistocene ◽

Model Parameters ◽

Ice Ages ◽

Glacial Cycles ◽

Orbital Parameters ◽

Ice Volume ◽

Astronomical Forcing

Variations of the Earth&#8217;s orbital parameters are known to pace the ice volume variations of the last million year [1], even if the precise mechanisms remain unknown. Several conceptual models have been used to try to better understand the connection between ice-sheet changes and the astronomical forcing. An often overlooked question is to decide which astronomical forcing can best explain the observed cycles.A rather traditional practice was to use the insolation at a some specific day of the year, for instance at mid-july [2] or at the june solstice [3]. But it was also suggested that the integrated forcing above some given threshold could be a better alternative [4]. In a more recent paper, Tzedakis et al. [5] have shown that simple rules, based on the original Milankovitch forcing or caloric seasons, could also be used to explain the timing of ice ages. Here we adapt and simplify the conceptual model of Parrenin and Paillard 2003 [6], to first reduce the set of parameters. Like in the original conceptual model from [6], this simplified conceptual model is based on climate oscillations between two states: glaciation and deglaciation. It switches to one another when crossing a defined threshold. While the triggering of glaciations is only triggered by orbital parameters, the triggering of deglaciations is triggered by a combination of orbital parameters and ice volume. Then, we apply the different possible forcings listed above and we try to adapt the model parameters to reproduce the ice volume record, at least in a qualitative way. This allows us to discuss which kind of astronomical forcing better explains the Quaternary ice ages, in the context of such simple threshold-based models.[1] Variations in the Earth's Orbit: Pacemaker of the Ice Ages, Hays et al., 1976, Science&#8232;[2] Modeling the Climatic Response to Orbital Variations, Imbrie and Imbrie, 1980, Science&#8232;[3] The timing of Pleistocene glaciations from a simple multiple-state climate model, Paillard, 1998, Nature[4] Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing, Huybers et al., 2006, Science[5] A simple rule to determine which insolation cycles lead to interglacials, Tzedakis et al., 2017, Nature[6] Amplitude and phase of glacial cycles from a conceptual model, Parrenin Paillard, 2003, EPSL.

Download Full-text

Dynamics of the Law Dome Ice Cap, Antarctica, as Found From Bore-Hole Measurements

Annals of Glaciology ◽

10.3189/s0260305500006947 ◽

1989 ◽

Vol 12 ◽

pp. 46-50 ◽

Cited By ~ 3

Author(s):

D.M. Etheridge

Keyword(s):

Shear Strain ◽

Vertical Velocity ◽

Flow Line ◽

Velocity Profiles ◽

Surface Velocity ◽

Ice Thickness ◽

Shear Strain Rate ◽

Orientation Data ◽

Ice Cap ◽

The Law

The internal dynamics of the Law Dome ice cap have been investigated by measuring the deformation of three bore holes located on an approximate flow line. Bore holes BHC1 (300 m deep) and BHC2 (344 m) were drilled in the coastal area to within several metres of bedrock and BHQ (418 m) was drilled about half-way towards the dome centre to about 50% of the ice thickness. Detailed measurements of orientation (inclination and azimuth), diameter, and temperature were taken through each bore hole over a 1 year span for BHC1 and BHC2 and a 10 year span for BHQ. The orientation data were reduced to obtain ∂u/∂z, a measure of the shear strain-rate. Changes in the depth of features located by bore-hole diameter measurements were used to obtain vertical velocity profiles. Other measurements discussed are temperatures, oxygen isotopes, crystal structure, surface velocities, and surface and bedrock topography.At the coastal sites, the ∂u/∂z profiles show two maxima in the lower third of the ice sheet. Flow due to the measured deformation accounts for about 55% of the surface velocity, the remainder being due to deformation and sliding in the basal zone. The vertical velocity profiles show mostly firn compression. The deeper ∂u/∂z maximum occurs in ice from the Wisconsin period which appears to deform more rapidly than the Holocene ice immediately above. The upper ∂u/∂z maximum may be related to the stress history of the ice, which can also explain the presence of significant shear strain and crystal-fabric development at only half the ice thickness at the BHQ site.

Download Full-text

Estimating the ice thickness of mountain glaciers with a shape optimization algorithm using surface topography and mass-balance

Journal of Inverse and Ill-Posed Problems ◽

10.1515/jip-2013-0016 ◽

2014 ◽

Vol 22 (6) ◽

Cited By ~ 2

Author(s):

Laurent Michel ◽

Marco Picasso ◽

Daniel Farinotti ◽

Andreas Bauder ◽

Martin Funk ◽

...

Keyword(s):

Shape Optimization ◽

Mass Balance ◽

Surface Topography ◽

Optimization Algorithm ◽

Moving Boundary ◽

Thickness Distribution ◽

Ice Thickness ◽

Surface Geometry ◽

Mountain Glacier ◽

Surface Mass

AbstractWe present a shape optimization algorithm to estimate the ice thickness distribution within a two-dimensional, non-sliding mountain glacier, given a transient surface geometry and a mass-balance distribution. The approach is based on the minimization of the surface topography misfit at the end of the glacier's evolution in the shallow ice approximation of ice flow. Neither filtering of the surface topography where its gradient vanishes nor interpolation of the basal shear stress is involved. Novelty of the presented shape optimization algorithm is the use of surface topography and mass-balance only within a time-dependent Lagrangian approach for moving-boundary glaciers. On real-world inspired geometries, it is shown to produce estimations of even better quality in smaller time than the recently proposed steady and transient inverse methods. A sensitivity analysis completes the study and evinces the method's higher susceptibility to perturbations in the surface topography than in surface mass-balance or rate factor.

Download Full-text