Changes in ice thickness and flow velocity of Yala Glacier, Langtang Himal, Nepal, from 1982 to 2009

Abstract To investigate recent glacier changes in the Himalayan region, we carried out GPS and ground-penetrating radar (GPR) measurements at Yala Glacier, a benchmark glacier in Nepal. Glacier surface elevation and ice thickness were surveyed along a 1.5 km profile from the glacier top to the terminus. Ice flow velocity was measured at five locations by surveying stakes for either 1 year or 4 day periods. Obtained surface elevation and ice velocity were compared with those measured in 1982 and 1996. The mean ice thickness along the radar profile was 36 m in 2009 and the ice has been thinning at rates of-0.69 ±0.25 and -0.75 ± 0.24 m a-1 during the periods 1982-96 and 1996-2009, respectively. The thinning rate increases down-glacier, reaching a magnitude up to -1.8 m a-1 near the terminus from 1996 to 2009. The ice velocity has reduced by >70% from 1982 to 2009 in the lower half of the glacier. By assuming a constant driving stress over the glacier, the total ice volume in 2009 was estimated as 0.061 km3. Our results indicate that Yala Glacier has lost ∼40% of its ice volume over the last 27 years and that the rate of the mass loss has accelerated over the last decade.

Download Full-text

The bedrock topography of Gries- and Findelengletscher

Geographica Helvetica ◽

10.5194/gh-73-1-2018 ◽

2018 ◽

Vol 73 (1) ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Nadine Feiger ◽

Matthias Huss ◽

Silvan Leinss ◽

Leo Sold ◽

Daniel Farinotti

Keyword(s):

Spatial Interpolation ◽

Thickness Distribution ◽

Estimation Method ◽

Ice Thickness ◽

Glacier Surface ◽

Ice Flow ◽

Bedrock Topography ◽

Abstract Knowledge ◽

Ground Penetrating ◽

Item Item

Abstract. Knowledge of the ice thickness distribution of glaciers is important for glaciological and hydrological applications. In this contribution, we present two updated bedrock topographies and ice thickness distributions for Gries- and Findelengletscher, Switzerland. The results are based on ground-penetrating radar (GPR) measurements collected in spring 2015 and already-existing data. The GPR data are analysed using ReflexW software and interpolated by using the ice thickness estimation method (ITEM). ITEM calculates the thickness distribution by using principles of ice flow dynamics and characteristics of the glacier surface. We show that using such a technique has a significance advantage compared to a direct interpolation of the measurements, especially for glacier areas that are sparsely covered by GPR data. The uncertainties deriving from both the interpretation of the GPR signal and the spatial interpolation through ITEM are quantified separately, showing that, in our case, GPR signal interpretation is a major source of uncertainty. The results show a total glacier volume of 0.28±0.06 and 1.00±0.34 km3 for Gries- and Findelengletscher, respectively, with corresponding average ice thicknesses of 56.8±12.7 and 56.3±19.6 m.

Download Full-text

Global mapping of surface flow velocity and re-evaluation of the volume of the world's glaciers

10.5194/egusphere-egu21-1066 ◽

2021 ◽

Author(s):

Romain Millan ◽

Jérémie Mouginot ◽

Antoine Rabatel ◽

Mathieu Morlighem

Keyword(s):

Water Resources ◽

Flow Velocity ◽

Sea Level ◽

Surface Flow ◽

Glacier Surface ◽

Ice Flow ◽

Ice Volume ◽

The World ◽

Global Mapping ◽

Flow Velocities

The effects of climate change on water resources and sea level are largely determined by the size of the ice reservoirs around the world, which still remains largely uncertain. Ice flow defines the transfer of ice within a glacier and therefore largely governs the spatial distribution of the ice volume. Although some individual regions have been mapped, there is to date no global and complete view of glacier flow. In this study, we present a global mapping of surface ice flow velocity and use it to revise the ice thickness distribution and volume of glaciers around the world. Glacier surface flow velocities were calculated using Sentinel-2/ESA, Landsat-8/USGS, Ven&#956;s/CNES-ISA, Pl&#233;iades/AirbusD&S and radar data from Sentinel-1/ESA. We designed an automated workflow that (i) downloads the data from institutional or commercial servers, (ii) prepares the images, (iii) launches the feature tracking algorithm, (iv) calibrate the glacier surface velocities, and (v) mosaics the results to obtain filtered and averaged velocity maps. For years 2017 and 2018, glacier surface flow velocities are quantified for every possible repeat cycles from the nominal cycle of the sensor (2-16 days) up to more than one year. This new database of glacier surface flow velocity is used to construct an updated global ice volume based on the well known Shallow Ice Approximation approach. We discuss the quality of our global glacier surface flow velocity product and of our new ice volume reconstruction with respect to existing state of the art estimates and quantify the impact of our results in terms of sea level rise and water resources.

Download Full-text

Recent variations in the terminus position, ice velocity and surface elevation of Langhovde Glacier, East Antarctica

Antarctic Science ◽

10.1017/s0954102014000364 ◽

2014 ◽

Vol 26 (6) ◽

pp. 636-645 ◽

Cited By ~ 8

Author(s):

Takehiro Fukuda ◽

Shin Sugiyama ◽

Takanobu Sawagaki ◽

Kazuki Nakamura

Keyword(s):

Sea Ice ◽

Flow Velocity ◽

Stable Condition ◽

Field Measurements ◽

East Antarctica ◽

Surface Elevation ◽

Ice Flow ◽

Glacier Terminus ◽

Ice Conditions ◽

Ice Velocity

AbstractTo improve the understanding of the mechanism driving recent changes in outlet glaciers in East Antarctica, we measured changes in the terminus position, ice flow velocity and surface elevation of the Langhovde Glacier located on the Sôya Coast. From satellite images from 2000–12 and field measurements taken in 2012 the glacier terminus position and flow velocity showed little change between 2003 and 2007. After this quiescent period, the glacier progressively advanced by 380 m and the flow velocity increased near the calving front by 10 m a-1 from 2007–10. No significant change was observed in surface elevation during the study period. The changes in the terminus position and flow velocity imply a reduction in the calving rate from 93 m a-1 (2003–07) to 16 m a-1 (2007–10). This suggests that calving was inhibited by stable sea ice conditions in the ocean. Theses results indicate that the Langhovde Glacier was in a relatively stable condition during the study period, and its terminus position was controlled by the rate of calving under the influence of sea ice conditions.

Download Full-text

A method to estimate the ice volume and ice-thickness distribution of alpine glaciers

Journal of Glaciology ◽

10.3189/002214309788816759 ◽

2009 ◽

Vol 55 (191) ◽

pp. 422-430 ◽

Cited By ~ 158

Author(s):

Daniel Farinotti ◽

Matthias Huss ◽

Andreas Bauder ◽

Martin Funk ◽

Martin Truffer

Keyword(s):

Mass Balance ◽

Thickness Distribution ◽

Ice Thickness ◽

Average Deviation ◽

Glacier Surface ◽

Ice Flow ◽

Thickness Change ◽

Ice Volume ◽

Alpine Glaciers ◽

Direct Measurements

AbstractSound knowledge of the ice volume and ice-thickness distribution of a glacier is essential for many glaciological applications. However, direct measurements of ice thickness are laborious, not feasible everywhere and necessarily restricted to a small number of glaciers. In this paper, we present a method to estimate the ice-thickness distribution and the total ice volume of alpine glaciers. This method is based on glacier mass turnover and principles of ice-flow mechanics. The required input data are the glacier surface topography, the glacier outline and a set of borders delineating different ‘ice-flow catchments’. Three parameters describe the distribution of the ‘apparent mass balance’, which is defined as the difference between the glacier surface mass balance and the rate of ice-thickness change, and two parameters define the ice-flow dynamics. The method was developed and validated on four alpine glaciers located in Switzerland, for which the bedrock topography is partially known from radio-echo soundings. The ice thickness along 82 cross-profiles can be reproduced with an average deviation of about 25% between the calculated and the measured ice thickness. The cross-sectional areas differ by less than 20% on average. This shows the potential of the method for estimating the ice-thickness distribution of alpine glaciers without the use of direct measurements.

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

Using Sequential Photography to Estimate Ice Velocity at the Terminus of Columbia Glacier, Alaska

Annals of Glaciology ◽

10.3189/s0260305500001270 ◽

1986 ◽

Vol 8 ◽

pp. 117-123 ◽

Cited By ~ 6

Author(s):

R.M. Krimmel ◽

L.A. Rasmussen

Keyword(s):

Time Resolution ◽

Principal Direction ◽

Film Plane ◽

Time Sequence ◽

Line Of Sight ◽

Glacier Surface ◽

Ice Flow ◽

Straight Line ◽

Camera Orientation ◽

Ice Velocity

The terminus of Columbia Glacier, Alaska, was observed with a single automatic 35 mm camera to determine velocity with a time resolution in the order of a day. The photographic coordinates of the image of a target were then transformed linearly into the direction numbers of the line of sight from the camera to the target. The camera orientation was determined from the film-plane locations of known landmark points by using an adaption of vertical photogrammetry techniques. The line of sight, when intersected with some mathematically-defined glacier surface, defines the true space coordinates of a target, The time sequence of a target’s position was smoothed, first in horizontal x, y space to a straight line, then in y (the principal direction of ice flow) and time with a smoothing cubic spline, and then the x-component was computed from the y-component by considering the inclination of the straight line. This allows daily velocities (about 8 m/day) to be measured at a distance of 5 km, using a 105 mm lens. Errors in daily displacements were estimated to be 1 m. The terminus configuration was also measured using the same photo set.

Download Full-text

On the errors involved in ice-thickness estimates I: ground-penetrating radar measurement errors

Journal of Glaciology ◽

10.1017/jog.2016.93 ◽

2016 ◽

Vol 62 (236) ◽

pp. 1008-1020 ◽

Cited By ~ 24

Author(s):

J.J. LAPAZARAN ◽

J. OTERO ◽

A. MARTÍN-ESPAÑOL ◽

F.J. NAVARRO

Keyword(s):

Ground Penetrating Radar ◽

Measurement Errors ◽

Ice Thickness ◽

Independent Components ◽

Ice Volume ◽

Thickness Error ◽

Grid Points ◽

Ground Penetrating ◽

Volume Estimates

ABSTRACTThis is the first (Paper I) of three companion papers focused respectively, on the estimates of the errors in ice thickness retrieved from pulsed ground-penetrating radar (GPR) data, on how to estimate the errors at the grid points of an ice-thickness DEM, and on how the latter errors, plus the boundary delineation errors, affect the ice-volume estimates. We here present a comprehensive analysis of the various errors involved in the computation of ice thickness from pulsed GPR data, assuming they have been properly migrated. We split the ice-thickness error into independent components that can be estimated separately. We consider, among others, the effects of the errors in radio-wave velocity and timing. A novel aspect is the estimate of the error in thickness due to the uncertainty in horizontal positioning of the GPR measurements, based on the local thickness gradient. Another novel contribution is the estimate of the horizontal positioning error of the GPR measurements due to the velocity of the GPR system while profiling, and the periods of GPS refreshing and GPR triggering. Their effects are particularly important for airborne profiling. We illustrate our methodology through a case study of Werenskioldbreen, Svalbard.

Download Full-text

Net Budget and Flow of South Cascade Glacier, Washington

Journal of Glaciology ◽

10.1017/s0022143000018608 ◽

1965 ◽

Vol 5 (41) ◽

pp. 547-566 ◽

Cited By ~ 78

Author(s):

Mark F. Meier ◽

W. V. Tangborn

Keyword(s):

Steady State ◽

Surface Elevation ◽

Elevation Change ◽

Glacier Surface ◽

Surface Elevation Change ◽

Long Valley ◽

Valley Glacier ◽

Ice Velocity ◽

The Mean ◽

Velocity Averages

AbstractIce velocity, net mass budget and surface elevation change data were collected over the length and width of a small (3.4 km. long) valley glacier from 1957 to 1964. Ice velocities range up to about 20 m./yr.; three prominent velocity maxima along the length of the glacier correspond to maxima in surface slope. Net mass budgets averaged over the glacier surface range between − 3.3 m. of water equivalent (1957–58) and +1.2 m. (1963–64). Except for the year 1960–61, curves of net budget versus altitude are parallel. During the period 1958–61 the glacier became thinner at a rate averaging 0.93 m./yr. The net budget and thinning data are internally consistent. Relations between emergence velocity, net budget and surface elevation change are examined at four specific points on the glacier surface and as functions of distance along the length of the glacier. Emergence velocity averages about −0.5 m. in the upper part of the glacier and about +1.0 m. in the lower part. Ice discharge and ice thickness are also calculated as functions of distance. The discharge reaches a peak of 8.8 × 105m.3of ice per year 2.2 km. from the head of the glacier. The mean thickness of the glacier is about 83 m. A steady-state distribution of net budget is used to calculate a steady-state discharge, which is 2.2 times larger than the present discharge.

Download Full-text

On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure

Journal of Glaciology ◽

10.1017/s0022143000005918 ◽

1984 ◽

Vol 30 (105) ◽

pp. 180-187 ◽

Cited By ~ 94

Author(s):

Roger Leb. Hooke

Keyword(s):

Atmospheric Pressure ◽

Flow Direction ◽

Mechanical Energy ◽

Glacier Surface ◽

Ice Flow ◽

Small Perturbations ◽

Point Pressure ◽

Ice Velocity ◽

Glacial Landforms

AbstractRecent theoretical studies of glacier hydrology have assumed that subglacial conduits are completely filled with water under steady-state conditions. This, however, is not necessarily the case. Where discharges are larger than a few tens of liters per second and the down-glacier slope of the bed is more than a few degrees, the potential energy released by water descending this slope may be capable of melting the walls of a subglacial conduit many times faster than the conduit can close by plastic flow of the ice. As a result, the pressure in such tunnels may normally be atmospheric, or possibly even at the triple-point pressure if there is no open connection to the glacier surface. Simple calculations suggest that such pressures in subglacial conduits may be more common than heretofore anticipated.The positions of such “open” conduits may be unstable to small perturbations in discharge or ice velocity. This is because the mechanical energy available in excess of that needed to balance closure can instead offset the general flow of the ice. Conduits can thus trend diagonally across the direction of ice flow. If an increase in the angle which such a conduit makes with the ice flow direction also results in an increase in slope of the conduit, more mechanical energy will become available, resulting in a positive feedback process.Subglacial channels at atmospheric pressure may influence the origin and morphology of certain glacial landforms, such as eskers and “plastically-molded” features.

Download Full-text

Glacier surface elevation changes in Rongbuk Catchment of the Central Himalayas in the last four decades

10.5194/egusphere-egu2020-9125 ◽

2020 ◽

Author(s):

Qinghua Ye ◽

Wei Nie ◽

Yimin Chen ◽

Gang Li ◽

lide Tian ◽

...

Keyword(s):

Climate Modeling ◽

Melting Rate ◽

Surface Elevation ◽

High Mountain ◽

Glacier Surface ◽

Important Indicator ◽

Central Himalayas ◽

Glacier Melting ◽

Elevation Changes ◽

Thinning Rate

Glaciers in the central Himalayas are important water resources for the downstream habitants, and accelerating melting of the high mountain glaciers speed up with continuous warming. We summerized the geodetic glacier surface elevation changes (Dh) by 6 data sets at different time periods during 1974-2016 in RongbukCatchment(RC) on the northern slope of Mt. Qomolangma (Mt. Everest) in the Central Himalayas. The result showed that glacier Dh varied with altitude and time, from -0.29 &#177; 0.03m a-1 in 1974-2000, to -0.47 &#177;0.24 m a-1 in 1974-2006,and -0.48 &#177;0.16 m a-1 in 1974-2012. Dh increased to -0.60 &#177; 0.20 m a-1 in 2000-2012, then decreased to-0.46 &#177; 0.24 m a-1 in 2000-2014, and by -0.49 &#177; 0.08 m a-1 in 2000-2016, showing a diverse rate being up - down- a little up. However, it generally presented a similar glacier thinning rate by -0.46~-0.49 m a-1 in the last four decades since 1970s in RC according to Dh1974-2006, Dh1974-2012, Dh2000-2014, and Dh2000-2016. Local meteorological observations revealed that, to a first order, the glacier thinning rate was kept the same pace with the number of annual melting days (MD). In spite of the obviously arising summer air temperature (TS) in 2000-2014, a slowdown glacier melting rate by -391 mm w.e.a-1 occurred in 2000-2014 because of less melting days with more precipitation and less annual mean temperature(Tm). It shows that MD is another important indicator and controlling factor to evaluate or to estimate glacier melting trend, especially in hydrological or climate modeling.

Download Full-text