Determination Of Ice Thickness Research Articles

Discrimination Algorithm and Procedure of Snow Depth and Sea Ice Thickness Determination Using Measurements of the Vertical Ice Temperature Profile by the Ice-tethered Buoys.

Snow depth and sea ice thickness in the Polar Regions are significant indicators of climate change and have been measured over several decades by ice-tethered buoys. However, sea ice temperature profiles measured by ice-tethered buoys are rarely used to infer snow depth and sea ice thickness owing to the lack of automatic discrimination algorithms, restricting the use of the data for sea ice thermodynamics studies. In this study, snow depth and sea ice thickness were retrieved through the measurements of sea ice temperature profiles using discrimination algorithms of the change point and the maximum likelihood detection methods. The data measured by 50 ice-tethered buoys were used to evaluate the accuracy of the results determined by the algorithm. Influences on the seasonal sea ice thermodynamic state, vertical interval of temperature sensors on the buoys, and initial ice thickness on the estimation errors were also evaluated. The performance of the discrimination algorithm for the data from the Arctic and Antarctic regions was also compared. There were no identifiable differences between the estimation errors from the Arctic and Antarctica. Increases in both the interval of the temperature sensors and the initial ice thickness enlarged the error for the estimation of ice thickness. A procedure developed in this study strengthens the potential application of measurements from the ice-tethered buoys only with the measurements of the vertical temperature profile of the layer of snow-covered ice, but not the measurements of ice basal and surface positions using acoustic sounding.

Routine Determination of Ice Thickness by Energy Filtration

Routine Determination of Ice Thickness by Energy Filtration

Routine determination of ice thickness for cryo-EM grids.

Recent advances in instrumentation and automation have made cryo-EM a popular method for producing near-atomic resolution structures of a variety of proteins and complexes. Sample preparation is still a limiting factor in collecting high quality data. Thickness of the vitreous ice in which the particles are embedded is one of the many variables that need to be optimized for collection of the highest quality data. Here we present two methods, using either an energy filter or scattering outside the objective aperture, to measure ice thickness for potentially every image collected. Unlike geometrical or tomographic methods, these can be implemented directly in the single particle collection workflow without interrupting or significantly slowing down data collection. We describe the methods as implemented into the Leginon/Appion data collection workflow, along with some examples from test cases. Routine monitoring of ice thickness should prove helpful for optimizing sample preparation, data collection, and data processing.

Determination of Ice Thickness on Lakes and Canals Using Audio Sound

Determination of Ice Thickness on Lakes and Canals Using Audio Sound

Ice thickness determination with audio sound

The objective of this study is to determine the thickness of Ice by analyzing the sound spectrum generated by dispersion of lamb waves propagating in ice. In winters when the lakes and rivers freeze, it is important to know the thickness of the ice layer before one intends to walk on it. When we throw a stone on the ice layer, we can hear a fluting noise. This is recorded for different thicknesses of ice and the sound spectrum is compared with the results simulated using a parameterized model. This model is created using a combination of plane waves for different incident angles and frequencies to generate dispersion curves for different thicknesses of ice. The frequencies of the reflected sound are then compared with the frequencies of musical notes in order to assign different musical notes to different thicknesses of ice.

Application of radar and seismic methods for the investigation of temperate glaciers

The capabilities of seismic and radar methods for the study of ice sheets have been analysed by other authors in the past. The joint use of both techniques has allowed the comparison of information, such as ice thickness, retrieved from both sources. Though these methods, specially the radar sounding, have also been widely used for the study of polythermal and temperate glaciers, the literature lacks joint analysis of their use for the study of temperate glaciers, where physical processes absent in the cold ice masses come into play. We have used seismic and radar methods collected at Johnsons Glacier, a temperate ice mass located in Livingston Island (Antarctica), to show the glaciological information that can be retrieved from such data. The aspects considered include the determination of ice thickness, the retrieval of information concerning the internal structure of the glacier (distinction between accumulation and ablation zones, determination of the depth of the firn–ice transition, detection of buried crevasses), the estimation of physical parameters such as seismic and radio wave velocities, water content in temperate ice and firn density, and the use of radar and seismic data to infer the presence of water channels at the ice–bed interface and to determine the nature of subglacial sediments.

Ice Mass Balance and Ice Dynamics from Satellite Gravity Missions

An overview of advances in ice research which can be expected from future satellite gravity missions is given. We compare present and expected future accuracies of the ice mass balance of Antarctica which might be constrained to 0.1–0.3 mm/year of sea level equivalent by satellite gravity data. A key issue for the understanding of ice mass balance is the separation of secular and interannual variations. For this aim, one would strongly benefit from longer uninterrupted time series of gravity field variations (10 years or more). An accuracy of 0.01 mm/year for geoid time variability with a spatial resolution of 100 km would improve the separability of ice mass balance from mass change due to glacial isostatic adjustment and enable the determination of regional variations in ice mass balance within the ice sheets. Thereby the determination of ice compaction is critical for the exploitation of such high accuracy data. A further benefit of improved gravity field models from future satellite missions would be the improvement of the height reference in the polar areas, which is important for the study of coastal ice processes. Sea ice thickness determination and modelling of ice bottom topography could be improved as well.

The ice-thickness distribution of Unteraargletscher, Switzerland

AbstractResults from 15 years of work on glacier-bed mapping by radio-echo soundings on Finsteraar-, Lauteraar- and Unteraargletscher, Switzerland, are summarized, and a new and greatly improved map of the ice-thickness distribution presented. In contrast to the tongue of Unteraargletscher, its two main tributaries, Lauteraar and Finsteraar, are both deep and narrow, and ice-thickness determination depends on the detection of more than just the primary reflection. Migrating the data led to considerably improved bed determination. Wherever possible, additional information on ice thicknesses gained from numerous hot-water drillings to the glacier bed is used as an independent verification of the results of the radar measurements, and a fair agreement is found.

Probing Europa's hidden ocean from tidal effects on orbital dynamics

Recent observations of Europa suggest that the Jovian satellite may have a liquid ocean underneath its icy surface. Geophysical models indicate that the tidal Love number k2 has a strong dependence on the presence or absence of an ocean. The k2 dependence on the ice shell thickness is also significant. Measurements of the static and tidal gravity fields through their dynamic effects on the trajectory of a low Europan orbiter can be essential in the detection of an ocean and inference of other internal structures. Covariance analyses have been carried out to assess accuracies using simulated Doppler tracking data. With 15 days of tracking from 2 Earth stations, the uncertainties for k2, mantle libration amplitude and the epoch radial position of the spacecraft are expected to be 0.0004, 2.8 arcsec and 5.7 m, respectively. These tight constraints will strongly contribute to ocean detection and ice thickness determination when combined with altimeter measurements.

Ice flow and mass continuity of Shumsky Glacier in the Djungarski Alatau Range of Kazakhstan, Central Asia

The glaciological monitoring program on the Shumsky Glacier in the Djungarski Alatau Range of southeastern Kazakhstan has included measurements of horizontal surface ice flow velocity, net balance, and emergence velocity at a network of more than 200 stakes during 1967–1991, as well as mappings of the ice surface topography by double‐theodolite triangulation and determination of ice thickness and of bedrock topography by radio echo sounding in 1984. These observations are here evaluated together to deduce the long‐term average dynamic behavior of Shumsky Glacier. The glacier extends between 3100 and 4400 m with a total area of 3 km2 and length of nearly 4 km. Maximum surface velocity is 20 m yr−1 and maximum volume flux 9 × 105 m3 yr−1, located near the equilibrium line altitude around 3680 m. The ice‐volume‐equivalent net balance is +0.5 m yr−1 in the average over the accumulation area, changing to about −1.5 m yr−1 near the terminus. The submergent flow in the accumulation area changes to emergence of 1 m yr−1 in the lower glacier. The rate of ice thinning is less than 0.1 m yr−1 in the middle glacier, increases to 2.5 m yr−1 near the terminus, and averages 0.12 m yr−1 for the glacier as whole. In fact, the Shumsky glacier differs little from equilibrium, being in a more favorable location that the other glaciers of the Djungarski Alatau. However, trends toward slower ice flow, more negative net balance, and faster rate of ice thinning indicate response to a progressively adverse climatic environment.

Helicopter radiometer measurements of thin lake ice and oil spills on lakes and soil

We report the results of thermal radio emission measurements of oil spills on lakes and soil and of thin lake ice at wavelengths of 0.8 and 3 cm from an MI-8 helicopter in oil fields in Western Siberia. Methods of oil-film and ice thickness determination by measurements based on thermal radiation interference in a two-layer medium are developed.

An HF bi-phase shift keying radar: application to ice sounding in Western Alps and Spitsbergen glaciers

A low-frequency ground penetrating radar, developed for martian subsurface sounding (Mars 96 Mission) is presented. During the preliminary campaigns, its performances have been studied by ice thickness determination on various glaciers. This radar is a pulse-compression system designed in order to limit the necessary peak power. It involves the phase modulation of the transmitted pulse by coded sequences. By moving the radar along a profile on the surface, a continuous section of the reflected energy associated with dielectric permittivity contrasts is obtained. Modulating the transmitted pulse and matched filtering the received signal provide a significant depth penetration while preserving a satisfactory range resolution. This processing is efficient even if the echo is partially shortened or if the signal is modified by differential attenuation. A multichannel filtering based on the spectral properties of the signal is then applied to the section. Experimental results of ice sounding on glaciers show that the ice-bedrock interface can be identified at depths between 30 and 120 m.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electromagnetic reflection survey 1986 at the Inland Ice margin of the Pâkitsoq basin, central West Greenland

The first successful application of electromagnetic ref1ection (EMR) techniques for determination of ice thickness in the outermost margin of the Inland Ice adjacent to the Pâkitsoq basin took place in luly 1985 (Thorning et al., 1986). Although the survey was planned as a series of experiments to examine why previous attempts had not worked, the EMR data acquired were of very good quality and could be compiled into a preliminary map of ice thickness and a map of the subglacial topography over part of the region. Thus, by early 1986 it Rapp. Grønlands geol. Unders. 135, 87-95 (1987) was known that the method worked and could be compiled through to the final product. With the increasing interest in this region, which is the planned location of the first hydroelectric power plant in Greenland, it was necessary to return in 1986 to survey the area in greater detail and to extend the coverage to the east. This note describes the field work carried out in April 1986 and the subsequent compilation and analysis of the combined EMR data sets from 1985 and 1986.

Determination of ice thickness by magnetic methods at Nordbogletscher, South Greenland

The topographic relief hidden under glaciers and the Inland Ice plays an important role in the study of ice dynamics, and several methods have been applied to map the subglacial surface of the Inland Ice in areas of interest for hydropower investigations. Radar-echo soundings or electromagnetic reflection methods (EMR) have often given good results, but have largely failed over the western rim of the ice cap, where inhomogenities in the form of melted and refrozen layers, water bodies, and cracks in the ice scatter the radar wave to such an extent that no useful echo is returned. In the summer of 1984 the author was in South Greenland for other purposes (Thorning &amp; Boserup, this report), and it was decided to attempt to determine the ice thickness by magnetic profiling on the ice surface. Magnetic field measurements are not affected by the physical properties and structure of the ice, and thus it should theoretically be possibie to obtain results near the rim of the ice cap, where the EMR method has failed. Whether results could be obtained would depend on limiting factors such as the magnetic properties of the underlying rocks, instrument capabilities, sensitivity of correction and modelling methods, and the general ambiguity of potential field methods.

Australian Antarctic Ice Thickness Measurements and Sastrugi Observations, Mac-Robertson Land, 1957–58

The principal field activity of the A.N.A.R.E. party at Mawson during the 1957–58 summer was the determination of ice thickness along a section of the Antarctic plateau. In previous years the summer expeditions inland had concentrated on the survey and geology of the Prince Charles Mountains, south-east of Mawson. While this programme was continued in 1957–58 as opportunity presented, and in fact air photography of the ranges almost completed, the main I.G.Y. field effort was directed towards seismic ice-depth determinations. These were the responsibility of the Bureau of Mineral Resources, and a seismologist was seconded to the Antarctic Division, together with equipment for the purpose.The traverse made lay southwards from Mawson, following approximately the meridian 62° 08′ E. It was known from prior air reconnaissance that a south-westerly spur of the Prince Charles Mountains system cut across the route in the vicinity of lat. 73° to 74° S., but the exact location was unknown. The intention was to map this spur, then skirt it to the west and resume the seismic traverse southwards.