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

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

The bedrock topography of Starbuck Glacier, Antarctic Peninsula, as determined by radio-echo soundings and flow modeling

Annals of Glaciology ◽

10.3189/2014aog67a025 ◽

2014 ◽

Vol 55 (67) ◽

pp. 22-28 ◽

Cited By ~ 17

Author(s):

Daniel Farinotti ◽

Edward C. King ◽

Anika Albrecht ◽

Matthias Huss ◽

G. Hilmar Gudmundsson

Keyword(s):

Antarctic Peninsula ◽

Thickness Distribution ◽

Flow Speed ◽

Ice Thickness ◽

Ice Flow ◽

Bedrock Topography ◽

Radio Echo Sounding ◽

Field Season ◽

Thickness Measurements

AbstractA glacier-wide ice-thickness distribution and bedrock topography is presented for Starbuck Glacier, Antarctic Peninsula. The results are based on 90 km of ground-based radio-echo sounding lines collected during the 2012/13 field season. Cross-validation with ice-thickness measurements provided by NASA's IceBridge project reveals excellent agreement. Glacier-wide estimates are derived using a model that calculates distributed ice thickness, calibrated with the radio-echo soundings. Additional constraints are obtained from in situ ice flow-speed measurements and the surface topography. The results indicate a reverse-sloped bed extending from a riegel occurring ~ 5 km upstream of the current grounding line. The deepest parts of the glacier are as much as 500 m below sea level. The calculated total volume of 80.7 ± 7.2 km3 corresponds to an average ice thickness of 312 ± 30 m.

Download Full-text

Ice thickness, volume and subglacial relief of Ashuu-Tor, Bordu, Kara-Batkak and Golubina glaciers (Central-Asia) derived from GPR measurements and different approaching methods

10.5194/egusphere-egu2020-1649 ◽

2020 ◽

Author(s):

Lander Van Tricht ◽

Philippe Huybrechts ◽

Jonas Van Breedam ◽

Johannes Fuerst ◽

Oleg Rybak ◽

...

Keyword(s):

Central Asia ◽

Thickness Distribution ◽

Mass Conservation ◽

Tien Shan ◽

Ice Age ◽

Ice Thickness ◽

Mountain Range ◽

Lake Formation ◽

Ground Penetrating ◽

Thickness Measurements

Glaciers in the Tien Shan (Central-Asia) mountains contribute a considerable part of the freshwater used for irrigation and households in the dry lowland areas of Kyrgyzstan and its neighbouring countries. Since the Little Ice Age, the total ice mass in this mountain range has been decreasing significantly. However, accurate measurements of the current ice volume and ice thickness distribution in the Tien Shan remain scarce, and accurate data is largely lacking at the local scale. In 2016, 2017 and 2019, we organized 1-month field campaigns in Central-Asia to sound the ice thickness of four different glaciers in the Tien Shan using a Narod ground penetrating radar (GPR) system.Here, we present and discuss our in-situ ice thickness measurements of the four glaciers. We performed in total more than 1000 GPR soundings. We found a maximum ice thickness of 200 meters in the central part of the southern facing Ashuu-Tor glacier. On both Bordu and Golubina, we measured ice thicknesses up to 140 meters. Kara-Batkak was found to have the thinnest ice which is in agreement to the large average slope of this glacier. We extended all the ice thickness measurements to the entire glacier surfaces using three different methods based on the assumption of plastic flow (method 1) and the principle of mass conservation (method 2 & 3) and assessed their differences.In this research, we show a detailed ice thickness distribution of Ashuu-Tor, Bordu, Golubina and Kara-Batkak glaciers. This can be used for glaciological modelling and assessing ice and water storage. We also point out the locations of potential lake formation in bedrock overdeepenings as a succession of glacier retreat.

Download Full-text

Ice volume estimates for the Himalaya–Karakoram region: evaluating different methods

The Cryosphere Discussions ◽

10.5194/tcd-7-4813-2013 ◽

2013 ◽

Vol 7 (5) ◽

pp. 4813-4854 ◽

Cited By ~ 5

Author(s):

H. Frey ◽

H. Machguth ◽

M. Huss ◽

C. Huggel ◽

S. Bajracharya ◽

...

Keyword(s):

Thickness Distribution ◽

Critical Evaluation ◽

Estimation Method ◽

Ice Thickness ◽

Distribution Models ◽

Glacier Inventory ◽

Ice Volume ◽

Sensitivity Assessment ◽

Volume Estimates ◽

Thickness Measurements

Abstract. Ice volume estimates are crucial for assessing water reserves stored in glaciers. A variety of different methodologies exist but there is a lack of systematic comparative analysis thereof. Due to its large glacier coverage, such estimates are of particular interest for the Himalayan-Karakoram (HK) region. Here, three volume–area (V–A) relations, a slope-dependent estimation method, and two ice-thickness distribution models are applied to a complete glacier inventory of the HK region. An uncertainty and sensitivity assessment is performed to investigate the influence of the input glacier areas, and model approaches and parameters on the resulting total ice volumes. 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 km3 to 6455 km3, depending on the approach. Results from the ice thickness distribution models and the slope-dependent thickness estimations agree well with measured local ice thicknesses while V–A relations show stronger deviations. The study provides evidence on the significant effect of the selected method on results and underlines the importance of a careful and critical evaluation. More ice-thickness measurements are needed to improve models and results in the future.

Download Full-text

Ice volume distribution and implications on runoff projections in a glacierized catchment

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-7507-2012 ◽

2012 ◽

Vol 9 (6) ◽

pp. 7507-7541 ◽

Cited By ~ 1

Author(s):

J. Gabbi ◽

D. Farinotti ◽

A. Bauder ◽

H. Maurer

Keyword(s):

Thickness Distribution ◽

Regional Climate ◽

Accurate Determination ◽

Annual Runoff ◽

Ice Thickness ◽

Volume Distribution ◽

Ice Volume ◽

Runoff Decrease ◽

Ground Penetrating ◽

Thickness Measurements

Abstract. A dense network of helicopter-based ground penetrating radar (GPR) measurements was used to determine the ice-thickness distribution in the Mauvoisin region. The comprehensive set of ice-thickness measurements was combined with an ice-thickness estimation approach for an accurate determination of the bedrock. A total ice volume of 3.69 ± 0.11 km3 and a maximum ice-thickness of 290 m were found. The ice-thickness values were then employed as input for a combined glacio-hydrological model forced by most recent regional climate scenarios. This model provided glacier evolution and runoff projections. Runoff projections of the measured initial ice volume distribution show an increase in annual runoff of 4% in the next two decades, followed by a persistent runoff decrease until 2100. Finally, we checked the influence of the ice thickness distribution on runoff projections. Our analyses revealed that reliable estimates of the ice volume is essential. Wrong estimations of the total ice volume might even lead to deviations of the predicted general runoff trend.

Download Full-text

Ice volume distribution and implications on runoff projections in a glacierized catchment

Hydrology and Earth System Sciences ◽

10.5194/hess-16-4543-2012 ◽

2012 ◽

Vol 16 (12) ◽

pp. 4543-4556 ◽

Cited By ~ 37

Author(s):

J. Gabbi ◽

D. Farinotti ◽

A. Bauder ◽

H. Maurer

Keyword(s):

Thickness Distribution ◽

Regional Climate ◽

Accurate Determination ◽

Annual Runoff ◽

Ice Thickness ◽

Volume Distribution ◽

Ice Volume ◽

Runoff Decrease ◽

Ground Penetrating ◽

Thickness Measurements

Abstract. A dense network of helicopter-based ground-penetrating radar (GPR) measurements was used to determine the ice-thickness distribution in the Mauvoisin region. The comprehensive set of ice-thickness measurements was combined with an ice-thickness estimation approach for an accurate determination of the bedrock. A total ice volume of 3.69 ± 0.31 km3 and a maximum ice thickness of 290 m were found. The ice-thickness values were then employed as input for a combined glacio-hydrological model forced by most recent regional climate scenarios. This model provided glacier evolution and runoff projections for the period 2010–2100. Runoff projections of the measured initial ice volume distribution show an increase in annual runoff of 4% in the next two decades, followed by a persistent runoff decrease until 2100. Finally, we checked the influence of the ice-thickness distribution on runoff projections. Our analyses revealed that reliable estimates of the ice volume are essential for modelling future glacier and runoff evolution. Wrong estimations of the total ice volume might even lead to deviations of the predicted general runoff trend.

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

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

Journal of Glaciology ◽

10.1017/jog.2021.11 ◽

2021 ◽

pp. 1-13

Author(s):

Iben Koldtoft ◽

Aslak Grinsted ◽

Bo M. Vinther ◽

Christine S. Hvidberg

Keyword(s):

Surface Topography ◽

Climate Model ◽

Thickness Distribution ◽

High Elevation ◽

Surface Velocity ◽

Ice Thickness ◽

Model Parameters ◽

East Greenland ◽

Ice Volume ◽

Ice Cap

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

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

Assessment with Controlled In-Situ Data of the Dependence of L-Band Radiometry on Sea-Ice Thickness

Remote Sensing ◽

10.3390/rs12040650 ◽

2020 ◽

Vol 12 (4) ◽

pp. 650

Author(s):

Pablo Sánchez-Gámez ◽

Carolina Gabarro ◽

Antonio Turiel ◽

Marcos Portabella

Keyword(s):

Soil Moisture ◽

Sea Ice ◽

Brightness Temperature ◽

European Space Agency ◽

Ground Truth ◽

Ice Thickness ◽

Sea Ice Thickness ◽

In Situ Data ◽

L Band

The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) and the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) missions are providing brightness temperature measurements at 1.4 GHz (L-band) for about 10 and 4 years respectively. One of the new areas of geophysical exploitation of L-band radiometry is on thin (i.e., less than 1 m) Sea Ice Thickness (SIT), for which theoretical and empirical retrieval methods have been proposed. However, a comprehensive validation of SIT products has been hindered by the lack of suitable ground truth. The in-situ SIT datasets most commonly used for validation are affected by one important limitation: They are available mainly during late winter and spring months, when sea ice is fully developed and the thickness probability density function is wider than for autumn ice and less representative at the satellite spatial resolution. Using Upward Looking Sonar (ULS) data from the Woods Hole Oceanographic Institution (WHOI), acquired all year round, permits overcoming the mentioned limitation, thus improving the characterization of the L-band brightness temperature response to changes in thin SIT. State-of-the-art satellite SIT products and the Cumulative Freezing Degree Days (CFDD) model are verified against the ULS ground truth. The results show that the L-band SIT can be meaningfully retrieved up to 0.6 m, although the signal starts to saturate at 0.3 m. In contrast, despite the simplicity of the CFDD model, its predicted SIT values correlate very well with the ULS in-situ data during the sea ice growth season. The comparison between the CFDD SIT and the current L-band SIT products shows that both the sea ice concentration and the season are fundamental factors influencing the quality of the thickness retrieval from L-band satellites.

Download Full-text

Comparison of Electromagnetic and Seismic-Gravity Ice Thickness Measurements in East Antarctica

Journal of Glaciology ◽

10.3189/s002214300003433x ◽

1975 ◽

Vol 15 (73) ◽

pp. 137-150 ◽

Cited By ~ 5

Author(s):

David J. Drewry

Keyword(s):

Seismic Reflection ◽

East Antarctica ◽

Ice Thickness ◽

South Pole ◽

Victoria Land ◽

Radio Echo Sounding ◽

Mean Differences ◽

Thickness Measurements ◽

Better Than ◽

Echo Sounding

AbstractThe errors involved in ice thickness determinations in Antarctica by seismic reflection shooting, gravity observations and radio-echo sounding are briefly discussed. Relative accuracies of 3%, 7-10% and 1.5% have been suggested. Double checks of ice depths from radar sounding in east Antarctica indicate an internal consistency of measurement for this technique of <1%. Comparison of carefully executed seismic shooting and routine radio-echo sounding results against absolute ice thickness values from two deep core drilling sites show no significant differences between these two remote methods (i.e. both are better than 1.5%).Over 60 comparisons are examined between radar ice thicknesses and over-snow measurements obtained on eight independent traverses in east Antarctica. Three traverses exhibit consistently unacceptable results-U.S. Victoria Land Traverse II (southern leg), Commonwealth Transanlarctic Expedition and the U.S.S.R. Vostok to South Pole Traverse—which probably result from misinterpretation of “noisy” seismograms. The remaining comparisons indicate mean differences, including some navigational uncertainty, of ≈3%, <8% and 5% between radio-echo and (1) seismic, (2) gravity, and (3) gravity tied to seismic determinations, respectively.

Download Full-text