bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nimbus-7 SMMR Derived Global Snow Cover Parameters
Authors: Chang A.T.C. , Foster J.L. , Hall D.K. 
Published: February 2017

Snow covers about 40 million km2of the land area of the Northern Hemisphere during the winter season. The accumulation and depletion of snow is dynamically coupled with global hydrological and climatological processes. Snow covered area and snow water equivalent are two essential measurements. Snow cover maps are produced routinely by the National Environmental Satellite Data and Information Service of the National Oceanic and Atmospheric Administration (NOAA/NESDIS) and by the US Air Force Global Weather Center (USAFGWC). The snow covered area reported by these two groups sometimes differs by several million km2, Preliminary analysis is performed to evaluate the accuracy of these products.Microwave radiation penetrating through clouds and snowpacks could provide depth and water equivalent information about snow fields. Based on theoretical calculations, snow covered area and snow water equivalent retrieval algorithms have been developed. Snow cover maps for the Northern Hemisphere have been derived from Nimbus-7 SMMR data for a period of six years (1978–1984). Intercomparisons of SMMR, NOAA/NESDIS and USAFGWC snow maps have been conducted to evaluate and assess the accuracy of SMMR derived snow maps. The total snow covered area derived from SMMR is usually about 10% less than the other two products. This is because passive microwave sensors cannot detect shallow, dry snow which is less than 5 cm in depth. The major geographic regions in which the differences among these three products are the greatest are in central Asia and western China. Future study is required to determine the absolute accuracy of each product.Preliminary snow water equivalent maps have also been produced. Comparisons are made between retrieved snow water equivalent over large area and available snow depth measurements. The results of the comparisons are good for uniform snow covered areas, such as the Canadian high plains and the Russian steppes. Heavily forested and mountainous areas tend to mask out the microwave snow signatures and thus comparisons with measured water equivalent are poorer in those areas.
Seasat Altimeter Observations of an Antarctic “Lake”
Authors: Cudlip W. , McIntyre N.F. 
Published: February 2017

The word “lake” in the context of Antarctica has been used to describe both surface features (10–12 km in size) and areas of liquid water on the bedrock beneath the ice sheet (typically a few kilometres in size and at a depth of over 3000 m), There has been however only limited evidence for a relationship between the two phenomena.This paper reports an analysis of Seasat altimeter observations of an extremely flat area on the surface of the East Antarctic ice sheet, approximately 30 km in extent, centred at 68.6°S 136.0°E and close to the edge of the sub-glacial Astrolabe Basin. It has a regional slope of between zero and 0.01° , and non-random variations in height along track of about ± 1m on the scale of a few kilometres. The average radar backscatter coefficient is 5±2 dB in the region of the Astrolabe Basin, compared to a more usual value of about 10 dB for other areas of the ice sheet. A computer enhanced Landsat image of the region clearly shows the rougher steeper terrain to the North, with the surface in and around the flat area appearing totally smooth and featureless.NSF/SPRI/TUD radio echo-sounding data from the region, although limited in extent, shows a relatively strong signal (indicative of ice at the pressure melting point) over a large region. The signal under the flat area, however, is particularly strong and smooth, confirming the association between the surface feature and a bedrock lake 3800 m below.
Characteristics of The Seasonal Sea Ice of East Antarctica and Comparisons with Satellite Observations
Authors: Jacka T.H. , Allison I. , Thwaites R. , Wilson J.C. 
Published: February 2017

A cruise to Antarctic waters from late October to mid December 1985 provided the opportunity to study characteristics of the seasonal sea ice from a time close to that of maximum extent through early spring decay. The area covered by the observations extends from the northern ice limit to the Antarctic coast between long. 50 °E and 80 E. Shipboard observations included ice extent, type and thickness, and snow depth. Ice cores were drilled at several sites, providing data on salinity and structure.
The observations verify the highly dynamic and divergent nature of the Antarctic seasonal sea-ice 2one. Floe size and thickness varied greatly at all locations, although generally increasing from north to south. A high percentage of the total ice mass exhibited a frazil crystal structure, indicative of the existence of open water in the vicinity.
The ground based observations are compared with observations from satellite sensors. The remote sensing data include the visual channel imagery from NOAA 6, NOAA 9, and Meteor 11. Comparisons are made with the operational ice charts produced (mainly from satellite data) by the Joint Ice Center, and with the analyses available by facsimile from Molodezhnaya.
Interpolation Techniques for the Display of Remotely Sensed Glaciological Data (Abstract)
Authors: Cooper A.P.R. 
Published: February 2017

The use of many display techniques for remotely sensed glaciological data requires the reduction of the data to a regularly spaced rectangular grid of values. Most remotely sensed data are not immediately suitable for display, because the area of interest is covered by more than one set of data on mutually incompatible grids (e.g. Landsat, AVHRR), or because the data are available as profiles along widely spaced ground tracks (e.g. radio echo-sounding, satellite altimetry). In addition, data may be sparsely and randomly scattered (e.g. surface elevations from TWERLE balloons).
A variety of techniques is available to reduce data to a specified grid system. These include spatial averaging, interpolation from nearest neighbours, and surface-fitting techniques, notably polynomial fitting and bi-cubic splines. All of these are useful under differing circumstances.
Characteristics of Altimetry Signatures Over Sea Ice (Abstract)
Authors: McIntyre N.F. , Laxon S.W. 
Published: February 2017

We report characteristics of Seasat altimetry signatures recorded over Antarctic sea ice. Up to four discrete zones can at times be seen in characteristic sequences in the Weddell and Ross Seas, and elsewhere. They are substantially larger than those reported in the Arctic, covering up to 2500 km at the time of maximum ice extent in 1978. Transitions between them can be abrupt, with marked changes occurring in less than a few kilometres. Some zones were found to persist through the 3 month satellite lifetime; others exhibited intermittent variations. Repeat data coverage has enabled temporal as well as spatial patterns to be investigated.
Interpretation of the geophysical cause of the patterns observed has been limited by available data. Some comparisons may be made with surface measurements of nadir back-scatter on first- and multi-year floes but these account for only a small proportion of the altimetry returns studied. Correlations with the NOAA Navy Ice Charts show significant disparities in the determination of the ice edge which may relate to the sensitivity of the altimeter to the presence of fresh ice or ice in very small quantities. Similar signatures can be found next to small coastal leads at the continental margin, an area known to be important for the growth of new ice.
Acoustic Emission Methods Applied to Avalanche-Formation Studies (Abstract)
Authors: Epifanov V.P. , Kuz’menko V.P. 
Published: February 2017

The relationship between the intensity of snow acoustic emission impulses and snow-cover stability is revealed by measuring the physical and mechanical properties of the snow cover in the starting zones of avalanches. This relationship is fundamental to the remote identification of an avalanche-hazard period.
In order to estimate the mechanical properties of a snow layer, a method of applying a rigid penetrometer equipped with a piezoelectric accelerometer is used. The viscosity coefficients of snow under destruction and the specific energy of destruction are determined. The overall effect of the different elements of destruction is assessed using both structural investigations and acoustic methods (acoustic emissions).
Methods of Calculation and Remote-Sensing Measurements for the Spatial Distribution of Glacier Annual Mass Balances (Abstract)
Authors: Konovalov V.G. 
Published: February 2017

The areal distribution of glacier annual mass balance b(z) is an important characteristic of the existence of glacierization and its evolution. At present the measured value of annual mass balance at different elevations is only available for a limited number of mountain glaciers of the globe, because of the great amount of labour required for such measurements.
The analysis of long-term mass-balance measurements made at Abramova Glacier, Limmerngletscher, White Glacier, Hintereisferner, and Peyto Glacier has revealed that for each year the spatial distribution of annual mass balance is well described by quadratic equations. The main variable in these equations is altitude (z). The various parameters of these formulae are estimated by the author for mean weighted height of the ablation and accumulation areas, and for the glaciers as a whole. It is found that the parameters of annual mass balance for each glacier can be calculated from formulae which include combinations of the following variables: annual balance at one of the three weighted altitudes, maximum annual snow-line elevation, annual and seasonal amounts of precipitation, and air temperatures at nearby meteorological stations.
Therefore, in order to calculate the distribution of annual mass balance as a function of absolute altitude, it is sufficient to obtain a value for mass balance measured only at a single point on a glacier, and common meteorological observational data. A comparison of actual and calculated values of mass balance has shown good agreement between them.
Considering the successful use of aerial remote-sensing for the measurement of snow depth in mountains by means of special stakes, it is satisfactory to accept this method for the assessment of annual mass balance at the mean weighted altitude of the ablation zone. It is possible to use aerial photo-surveys or stereophotogrammetry to resolve this problem. Then annual mass balance for the whole area of a glacier is calculated by using data from one point together with data from a nearby meteorological station.
An Experiment on Image Transmission to an Icebreaker (Abstract)
Authors: Korhonen O. 
Published: February 2017

Finland has such a climate that all its harbours in the Baltic Sea are frozen every winter. Ice may sometimes be more than 1 m thick, as it was in the Bay of Bothnia, the northernmost basin of the Baltic Sea, during the winter of 1985.
The Finnish Institute of Marine Research has used the imagery of the Tiros-N series of satellites successfully in sea-ice mapping for some years. In the Institute daily ice charts have been prepared and sent by facsimile to icebreakers in the Baltic Sea. In 1985, an experiment was conducted to transmit the same imagery to an icebreaker operating in the Bay of Bothnia. Existing telecommunication networks were used. The image data transmitted by NOAA-6 and NOAA-9 satellites were received at Tromsø Telemetry Station in Norway and then transmitted to Espoo in Finland. The data processing consisted of geometric correction, edge enhancement, and drawing the coastline with location symbols. The most interesting area was extracted and transmitted by NMT mobile telephone to the icebreaker.
The almost real-time image transmission turned out to be useful from the point of view of icebreaker operation. The images could be used to identify cracks and narrow leads in the ice. Such very detailed information cannot be included in routine ice charts. The icebreaker can use this information for giving instructions to other ships to find easier routes. This reduces the need for icebreaker assistance. The images can also help the icebreaker to avoid wide heavily ridged areas.
This experiment was at low cost and can be technically developed further. It showed that this kind of assistance for icebreakers is economically profitable for winter navigation.
Spectral Response Patterns of Snow and Ice Surfaces for the Landsat Multispectral Scanner (Abstract)
Authors: Kristensen M. , McIntyre N.F. 
Published: February 2017

The high-resolution imagery recorded by systems such as the multi-spectral scanners (MSSs) of the Landsat satellites has revolutionized the study of all types of surface in the polar regions. Visible and near-infra-red imagery has found a wide range of glaciological uses. There is, however, a lack of comparability within and between MSS data which may be a contributary factor to some current problems in interpretation of remotely sensed glaciological data.
With the expected continuity of MSS coverage for the forseeable future, it is highly desirable to extend use of the data beyond the basic mapping and feature identification which has made it such a valuable resource. One of the most obvious developments is to investigate characteristics of the reflecting surfaces and to achieve absolute identification of snow and ice surfaces. Although conversion of digital MSS grey tones to radiances enables direct comparison with other sources, automatic identification requires detailed and extensive knowledge of the spectral and reflecting characteristics of surfaces which are to be monitored. This is often best achieved through ground-based observation.
In order to provide a base line against which corrected radiances from Landsat MSS data can be compared, a spectrally gated photometer has been used to measure albedo at MSS wave bands in a wide range of conditions. The surfaces monitored in several parts of Norway include sea ice, lake ice, snow, firn and glacier ice, permafrost, and reference surfaces. A range of supporting measurements (including grain-size, surface irregularity, density, level, and free-water content) allows accurate characterization of each surface. This enables identification of spectral-response patterns for each surface category and hence the classification of their reflectances as recorded by the MSS. Examples are given of the application of such classifications to imagery of the polar regions.
Remote Sensing of Fast Ice in Lützowholmbukta, East Antarctica, using Satellite NOAA-7, 8 and Aircraft (Abstract)
Authors: Mae S. , Yamanouchi T. , Fujii Y. 
Published: February 2017

Lützowholmbukta, East Antarctica, is covered by fast ice except during a short period in April and May, but occasionally the ice cover breaks up and floats out of the bay.
The fast ice was observed every day using NOAA-7, 8 infra-red imagery. The satellite signal was received at Syowa Station, located on Ongul Island. In addition, aerial photographs and video pictures were taken using aircraft every fortnight.
In 1983, before the break-up of the fast ice in April, a distinctive increase of the infra-red radiance (NOAA AVHRR) was observed, even though the aerial observation showed no change. The increase of the radiance was estimated to be 5°C. It was in this area, where the higher infra-red signal was observed, where the fast ice broke up. In December, in the central part of the northern area of the fast ice, the hummock-ice zone formed in a triangular shape. Before the hummock-ice zone floated out, observation of the infra-red radiance showed that the temperature of the ice had decreased by 3°C.
Comparison of Surface Characteristics of the Antarctic Ice Sheet with Satellite Observations (Abstract)
Authors: Young N. , Goodwin I. 
Published: February 2017

Ground surveys of the ice sheet in Wilkes Land, Antarctica, have been made on oversnow traverses operating out of Casey. Data collected include surface elevation, accumulation rate, snow temperature, and physical characteristics of the snow cover. By the nature of the surveys, the data are mostly restricted to line profiles. In some regions, aerial surveys of surface topography have been made over a grid network.
Satellite imagery and remote sensing are two means of extrapolating the results from measurements along lines to an areal presentation. They are also the only source of data over large areas of the continent. Landsat images in the visible and near infra-red wavelengths clearly depict many of the large- and small scale features of the surface. The intensity of the reflected radiation varies with the aspect and magnitude of the surface slope to reveal the surface topography. The multi-channel nature of the Landsat data is exploited to distinguish between different surface types through their different spectral signatures, e.g. bare ice, glaze, snow, etc. Additional information on surface type can be gained at a coarser scale from other satellite-borne sensors such as ESMR, SMMR, etc. Textural enhancement of the Landsat images reveals the surface micro-relief.
Features in the enhanced images are compared to ground-truth data from the traverse surveys to produce a classification of surface types across the images and to determine the magnitude of the surface topography and micro-relief observed. The images can then be used to monitor changes over time.
Glacier Volume Estimation on Cascade Volcanoes: An Analysis and Comparison with Other Methods
Authors: Driedger C.L. , Kennard P.M. 
Published: February 2017

During the 1980 eruption of Mount St. Helens, the occurrence of floods and mudflows made apparent a need to assess mudflow hazards on other Cascade volcanoes. A basic requirement for such analysis is information about the volume and distribution of snow and ice on these volcanoes.An analysis was made of the volume-estimation methods developed by previous authors and a volume- estimation method was developed for use in the Cascade Range. A radio echo-sounder, carried in a backpack, was used to make point measurements of ice thickness on major glaciers of four Cascade volcanoes (Mount Rainier, Washington; Mount Hood and the Three Sisters, Oregon; and Mount Shasta, California), These data were used to generate ice-thickness maps and bedrock topographic maps for developing and testing volume-estimation methods. Subsequently, the methods were applied to the unmeasured glaciers on those mountains and, as a test of the geographical extent of applicability, to glaciers beyond the Cascades having measured volumes.Two empirical relationships were required in order to predict volumes for all the glaciers. Generally, for glaciers less than 2.6 km in length, volume was found to be estimated best by using glacier area, raised to a power. For longer glaciers, volume was found to be estimated best by using a power law relationship, including slope and shear stress. The necessary variables can be estimated from topographic maps and aerial photographs.
Glacier Mapping to Confirm Results from Mass-Balance Measurements
Authors: Haakensen Nils 
Published: February 2017

Annual mass-balance measurements have been made at a number of glaciers in Norway since the beginning of the 1960s, A detailed and reliable map is necessary as a base for field work and more than twenty glacier maps have been constructed photogrammetrically at scales of 1:10 000 or 1:20 000 since 1952. For some of the glaciers more than one map has been constructed and changes in glacier volume can be calculated, provided the maps have sufficient accuracy.
For the glaciers, Nigardsbreen, Hellstugubreen, and Gråsubreen, two or more good maps are available and these form a good basis for comparisons and calculations of changes in volume between the years when the air photographs were taken.
Comparisons have been made for Gråsubreen between 1968 and 1984, for Hellstugubreen between 1968 and 1980, and for Nigardsbreen between 1964 and 1984.
The calculations are made by placing a 100 m grid on the glacier maps and comparing the altitude for corresponding points. The changes in height are regarded as representative for the 0.01 km2 glacier areas represented by each point.
Results from the investigation have been used to check the accuracy in cumulative mass balance for corresponding periods.
Repeated air photography, at intervals of 5—10 years, can be used in the future to find the cumulative mass balance for a great number of glaciers at lower cost than “normal” mass-balance work.
Main Results of Mapping Glacio-Nival Systems in the World Atlas of Snow and Ice Resources
Authors: Kotlyakov Vladimir M. , Dreyer Natalia N. , Kravtsova Valentina I. 
Published: February 2017

The compilation of the Atlas was based on the concept of glacio-nival systems (and the fields of these systems), developed in the U.S.S.R. It became possible to map glacionival systems by using all available data and by the development of indirect methods of obtaining regime parameters, characterising the glacio-nival zones. This, in turn, made it possible to show, on maps of different scales, properties relating to glacio-nival phenomena and processes, such as air temperature in a glacierized zone, the amount of solid and liquid precipitation, snow storage, the accumulation and surface ablation of glaciers and melt run-off.
The compilation of these maps has demonstrated their conformity and complementary nature, the principles of which were worked out in the course of creating the Atlas.
Based on the experience of compiling hundreds of various maps, the paper describes some peculiarities of depicting different elements of glacio-nival systems on maps of different scales and shows ways to overcome shortages of data in preparing the maps.
Photogrammetric and Satellite Mapping of the Margin of the Inland Ice, West Greenland
Authors: Thomsen H.H. 
Published: February 2017

Glaciological investigations have been carried out in areas proposed for local hydro-power stations in Greenland, A mapping programme was set up, to provide data for mass balance and simulation of run-off, as well as glacier dynamics.Two types of glacier map have been produced, covering the margin of the Inland Ice: detailed photogrammetric maps, based on plotting from vertical aerial photographs and a new type of surface feature map, based on digitally-processed Landsat data. The photogrammetric maps, plotted on a scale of 1:25 000, include surface topography and surface features, such as crevasses, lakes, moraines etc. The surface feature maps, plotted on a scale of 1:100 000, show surface features related to ice and melt-water drainage, as well as subtle, topographic features, related to the subglacial topography.The maps have so far been used for preliminary delineation of drainage areas on the Inland Ice and for planning tracks of radio echo-soundings.
Polar Firn Densification and Grain Growth
Authors: Alley Richard B. , Bolzan John F. , Whillans Ian M. 
Published: February 2017

A 50 m firn core from Dome C, East Antarctica, was found to consist of coarse firn, which comprised 90 to 95% of the core, and fine firn. Coarse firn was characterized by large crystals with a vertical shape orientation near the surface, connected to nearest neighbors by relatively large necks in a structure different from closest packing. Fine firn was of higher density and consisted of smaller, more spherical crystals connected by relatively narrow necks in a more nearly closest-packed configuration.Higher surface free energy in fine firn causes crystals and necks to grow more rapidly than in coarse firn. However, we find that coarse firn densifies more rapidly with time, contrary to the predictions of unconfined sintering models. Load-driven densification due to a power-law creep mechanism is found to account for the larger coarse-firn densification rate. However, if the exponent in the power law exceeds one, then densification rates are predicted to increase with depth due to increasing load, contrary to observed behavior. We speculate that different mechanisms may control the densification process in fine and coarse firn.