Research Article
Glaciological and Hydrological Map of the Hornsund Fiord Area: 1:75 000 (Abstract)
- J. Jania, M. Pulina
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- Published online by Cambridge University Press:
- 20 January 2017, p. 207
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The problem of how to select and synthesize glaciological and hydrological information for the map of South Spitsbergen is discussed. The area of interest covers aproximately 1700 km2, but not all of it has been explored equally well so far. The map is under preparation for printing. It is one of a series of environmental maps of Hornsund at 1:75 000. Geomorphology and geology have been completed already. The general objective was to reveal the spatial differentiation of glacial and hydrological phenomena in the vicinity of the Hornsund Fiord but particular interest was focused on providing synthesized information about glacial and hydrological phenomena and processes, which had been considered in the context of natural hydrological basins.
The result is a specification of the phenomena represented in the map. It had been divided into five parts;
(1) elements of geomorphology, geology (lithology) and topography (basemap);
(2) features of glaciers and glacial phenomena on land;
(3) physical and chemical properties of on-land streams and glacier streams;
(4) features of marine environment and Hornsund Fiord bottom (during contruction); and
(5) general characterization and classification of phenomena occurring in hydrological basins.
The first is of a general nature. Parts two, three and four include detailed, analytical information. Part five comprises synthesized data.
The glaciers of Hornsund are specified by morphological classification, according to PSFG of the IAHS, by the position of the mean firn line and major glacier zones, and by the pattern of the ice flow-lines, along with some information on the velocity of flow. Thermal classification of the glaciers, and data on the oscillations of the glacier fronts in the 20th century are presented.
Of the Hornsund glaciers, Werenskioldbreen (approximately 27 km2)has been exposed in the map at 1.25 000. It has roused the interest of many investigators and is amongst the best explored examples. The available set ot data pertaining to this glacier consists predominantly of analytical, quantifying information, e.g. on the changes of the glacier surface altitude which occurred from 1957 to 1983, on the net balance at selected points of the glacier, on the pattern of englacial and subglacial channels, on the discharge in glacial streams, and on the quantity and degree of mineralization and chemical content of glacial streams, etc.
The result is a coloured map which aims at representing, in a systematic and synthesized manner, contemporary phenomena and processes associated with the glaciers and the water system of the Hornsund Fiord basin.
Mapping Coastal Ice Cliffs and Icebergs From Altimetry Data (Abstract)
- R.H. Thomas, H. Jay Zwally
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- Published online by Cambridge University Press:
- 20 January 2017, p. 208
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In a recent paper, Thomas et.al. (1984) showed how the coast of Antarctica could be mapped using satellite altimetry data. As the satellite approached the continent from the ocean, the Seasat altimeter obtained strong reflections from sea ice, even for a short time after passing over the ice front. Measured ranges are actually oblique distances to the nearest portion of sea ice, yielding a false drop in surface elevation. From the sequence of oblique ranges during a single orbit crossing of the ice cliff, the horizontal position of a segment of the ice cliff is mapped. Currently, the entire Seasat data set is being analyzed to map most of the Antarctic coastline north of 72 °S to an accuracy of ± 0.1 to 1 km, which is a major improvement over existing surveys. The altimeter waveforms corresponding to each range measurement are computer analyzed (“retracked”), using procedures that account for the specular reflections from sea ice and the diffuse reflections from firn. Each waveform analysis, along with the corrected range for data obtained in the vicinity of an ice cliff crossing, is verified or recomputed on an interactive computer, which also computes and maps the position of the ice front. The locations of several tabular icebergs have also been mapped with the same procedures, which can ultimately be used to obtain an estimate of iceberg population density in polar waters, initial results include the mapping of the Larsen ice shelf on the eastern side of the Antarctic Peninsula, showing, for example, the protrusion at approximately 68.5 °S. Estimates of errors in the derived horizontal position are obtained from the analysis of data from repeating orbit tracks. Comparison of these results with results from future altimetry missions will reveal changes in the position of coastal ice cliffs, due to ice movement and/or iceberg calving. Systematic measurements over several years would probably distinguish the effects of iceberg calving, which is intermittent, from those of ice movement, which is continuous.
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Mapping the Extent and Duration of Surface Melting On Ice Sheets and Shelves (Abstract)
- H.Jay Zwally
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- Published online by Cambridge University Press:
- 20 January 2017, p. 209
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Research Article
Glacial Geomorphological Map (1:200 000) of Mt. Tomur Region, Tianshan (Abstract)
- Zheng Benxing
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- Published online by Cambridge University Press:
- 20 January 2017, p. 209
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The Glacial Geomorphological Map (1:200 000) of Mt, Tomur Region, Tianshan, covers 78°33′ – 81°10′E and 41° 08′ – 42° 44′N, with high mountains, deep valleys and many snow peaks, the highest being Mt. Tomur (7435.3 a.s.l.). There are many glaciers in this region with a total area of 4553.69 km2. The melt water from glaciers irrigates the large oasis of Aksu, in the piedmont region in southern Xingjiang and waters the valley plain of Teks River in the Yili area. From piedmont plain to highest mountain summit, the vertical zonality of geomorphology is quite clear, rich in various geomorphological types, representing alpine geomorphology of the arid desert in Central Asia.
The author joined the glacial/geomorphological expedition to the Mt. Tomur Region in 1963, 1973 and 1974, and, in the process of mapping, cooperated closely with mapping engineers. This involved extensive use of aerial photographs, satellite images, large-scale topographic maps, geological maps, geomorphological maps and other data, and comprehensive analyses, comparisons, and judgements of data.
Special emphasis was placed on existing glaciers and the geomorphology of Quaternary glaciers, according to form, composition and relative chronological periods. The geomorphology was divided into five great systems, i.e. glacial, fluvio-glacial, fluvial, arid and artificial. Twenty-four geomorphic types were defined as the basic elements of the geomorphological map and shown in different colours and by various marks, while old and Neozoic faults were shown by black line marks. There are representative heights on all geomorphological zones. Colour brush-shading added much to the stereo effect.
Below the main map, the longitudinal and cross sections of Quaternary geology and geomorphology of the Tialan valley, the stratigraphical columnar profile of West Zamtia and the fluvial/lacustrine deposit profile of the Loska basin were attached, showing the stratigraphical relation between the glacial and non-glacial deposit and the basis for the divisions of the glacial and inter-glacial periods.
Summary of Discussions
- Mark F. Meier
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- Published online by Cambridge University Press:
- 20 January 2017, p. 210
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In 1965, the first International Symposium on Glacier Mapping was held in Ottawa. This was convened at the beginning of the International Hydrological Decade, at a time of great expansion in glaciological research around the world. The purpose and scope of glacier mapping were well defined, perhaps for the first time, by the late Valter Schytt and others at the Symposium, It must be remembered that this symposium took place at a time when much of the technology we now take for granted did not exist. In some respects the symposium was prophetic: Gordon Robin suggested that the topography of the ice sheet might be measurable with an altimeter mounted in a satellite, and A.H. Waite, Jr. discussed the beginning attempts to sound glaciers using radio waves.
Now in 1985 a Symposium on the same subject has been concluded in Reykjavik. It is apparent that the interest generated in the first Symposium has had a real effect, and some dreams have come true. Jay Zwally reported that repeated satellite altimetry has measured growth of part of the Greenland Ice Sheet, and sophisticated radio echo-sounding programs are adding the third dimension to glacier mapping. And glacier mapping has progressed in many other new and exciting directions. However, problems remain. For instance, only 20% of the Antarctic continent has been mapped at a scale of 1:250 000 or larger and what maps do exist of Antarctica were compiled over long periods of time and cannot be precisely dated. There are still few maps of remote areas in the world and these often lack geographic coordinates and captions in a language of common international use. The navigation or positioning systems used in many large-scale mapping programs have not been as highly developed as they should be. Much glacier mapping data now exists in digital form, but many of the digital data bases can not be accessed internationally.
What are the needs for the future? First, we need wider application of digital data bases, including digital terrain models and geographic information systems. These should be set up so that the data can be retrieved by scientists from different countries, a difficult problem for parochial, technical, and political reasons. Attention needs to be given to long-term storage of digital data to insure against degradation with time. Once a good digital data base is established, the appropriate hard copy maps can be produced to whatever specifications are appropriate.
But computers will not solve everyone’s needs. We certainly will need, far into the future, classical paper maps, the so-called “hard copy” that displays all of the information the field glaciologist or traveller requires. Public display maps that show the topography in an artistic way that is clear to the inexperienced viewer will always be needed. Of course, all maps should have geographic coordinates and a legend in an international language, such as English, to meet the needs of the international community.
The quality of mapping will have to improve to meet tomorrow’s needs, This will include such things as improved definition of ice sheet surfaces, especially along ice divides so that flow patterns can be discerned. We need to integrate accurate positioning systems with the radio echo-sounding or other mapping systems. Repeated mapping of certain glaciers or ice mass areas, using similar mapping specifications, will be needed to detect change in these ice masses; such maps will have to be very precise in the measurement of surface ice elevation, We will certainly need “snapshot” maps of the large ice sheets, a task that can probably be accomplished only through the use of satellite technology. The field has come a long way in the last twenty years but it will probably progress far more in the next twenty.
I wish to thank all of the speakers and the participants and those who so superbly organized the Symposium for a most challenging and productive meeting. Thank you all very much.