摘要:

The article presents a summary of the present state of knowledge of perennial periglacial mounds, including descriptions of the external appearance and internal composition of pingos and palsas and a discussion of the genetic mechanisms. Pingos appear to be the result of the freezing of a mass of water trapped beneath permafrost under cryostatic or hydraulic pressure. Palsas are formed by the migration of groundwater to a freezing plane (cryosuction). The existence of mineral palsas is recognized; in this case the peat cover may be extremely thin or even totally non‐existent.

ISSN:0273-8457    

DOI:10.1080/10889378509377249

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Published paleogeographic reconstructions reveal pronounced differences between the North Atlantic and North Pacific regions in terms of oceanic circulation, glaciation and paleoclimate. However, the author's analysis, conducted with due regard for the laws of glacier‐ocean interrelations has allowed him to reach the conclusion that the paleogeography of the two regions under consideration was basically similar. This refers not only to the atmospheric and oceanic circulations but also to the distribution of ice domes and ice sheets on the continents and of ice shelves in marine areas. The development of marine ice sheets was closely linked to hydrological subarctic fronts in both oceans where mass‐ and energy‐exchange was most active in the ocean‐atmosphere system. The growing isolation of the Sea of Okhotsk and the Bering Sea caused by glacio‐eustatic regression interrupted the inflow of warm ocean water via the Tsushima and Aleutian currents respectively. These conditions in both oceans provided the basis for the development of a stable ice cover. Geological and geomorphological data appear to confirm these inferences.

ISSN:0273-8457    

DOI:10.1080/10889378509377250

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

For a long time Antarctic icebergs were carefully avoided and they were rarely examined scientifically. With the recognition of their potential as valuable sources of fresh water and energy, particularly for the arid zones, a dramatic surge of interest has been manifested by researchers representing a multiplicity of disciplines. Practical utilization of this natural resource now depends only on politically and economically based decisions.

ISSN:0273-8457    

DOI:10.1080/10889378509377251

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Sea ice observations in the Southern Ocean for the period 1956–1982 are interpreted and summarized and the general trends in sea ice occurrence, development and decay are described. Interannual variations with special emphasis on seasonal and year‐to‐year changes in the main elements of the sea ice regime are discussed: these include such elements as the extent of pack ice and the distribution of fast ice. Polynyas and ice massifs are also discussed. Volumes of both sea ice and icebergs at both their maximum and minimum extent, together with seasonal and spatial variations are discussed. The results obtained in terms of sea ice and icebergs differ considerably from previous estimates.

ISSN:0273-8457    

DOI:10.1080/10889378509377252

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Glaciogeomorphological, paleobotanical and geochronological investigations have permitted the identification of phases of glacier development on Svalbard during the Holocene. The following stages have been distinguished: Damesmorenen (about 7,800 yeaTS B.P.), Passdalen (4,500–4,000 years B.P.), Grønfjorden (3,000–2,500 years B.P.) and Treskelen (17th‐19th century). The Late Pleistocene‐Early Holocene stages of glacier advance distinguished earlier require more reliable chronological confirmation. An important peculiarity of the Holocene glaciation on Svalbard is that some of the glaciers reached their maximum dimensions at the beginning of the Holocene and others at the end, during the “Little Ice Age.”; This peculiarity of the glaciation of the archipelago during the Holocene has not yet been satisfactorily explained and requires further investigation.

ISSN:0273-8457    

DOI:10.1080/10889378509377253

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The authors present the results of repeated analyses of data from radio echo‐sounding surveys of Svalbard glaciers conducted in 1978–79 and using a frequency of 620 MHz. Data from surveys flown in 1974–75 and 1977–80 over Svalbard glaciers are also discussed. It has been established that glaciers with areas of up to 152km are characterized by maximum ice thicknesses of 200 m and relatively complex subglacial topography. Reticulated glaciers have much greater ice thicknesses; on ice plateaux they reach 585 m (Holtedahlfonna), and on twinned, outlet and valley glaciers 430–540 m or more (e.g., Recherchebreen‐Vestre Torellbreen, Mittag‐Lefflerbreen and Veteranen). Major rises in the subglacial bedrock have been detected in the ice‐divide areas of some twinned glacier systems. Glaciers occupying valleys are characterized by maximum ice thicknesses of 350–400 m (in the accumulation zone) and comparatively flat, even subglacial relief, extending for distances of 5–30 km. These glacier beds lie near or below sea level, down to depths of ‐100 or ‐200 m. In the case of ice caps overlying positive relief forms (e.g., Aasgaardfonna) maximum ice thicknesses vary between 100 and 350 m, while in the case of the Vestfonna, which has a comparatively flat bed, they reach 385 m. In general there are no significant differences in the distribution of ice thicknesses over the areas of reticulated glaciers in Svalbard. Data from radio echo‐sounding and ratios established between ice volume and glacier area allow one to calculate the total ice volume in the glaciers of the archipelago and to determine its distribution over particular glacierized areas. According to our revised figures the total ice volume is about 7,500 km3. Mean thicknesses of glaciers in the area of reticulated glaciers in Svalbard range from 140 m in the south to 170 m in the northeast. In the central area, mainly involving mountain glaciers, mean ice thicknesses are about 70 m. The mean thickness of all Svalbard glaciers is close to 200 m. The problem of radio echo‐sounding of the firn areas on large glaciers still remains unresolved. A possible solution would be to carry out the measurements during the cold period of the year; in general, too, it can be resolved by using equipment operating at lower frequencies.

ISSN:0273-8457    

DOI:10.1080/10889378509377254

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A map of paleotemperature anomalies at 10,500 B.P. for the North Atlantic and adjacent continents was compiled. It is based upon data from marine micropaleontological and palynological studies. The pattern of isotherms reveals that maximum negative anomalies occurred in the eastern subtropical North Atlantic between 35 and 45°N, reaching values of 8–9°C, i.e., double those recorded over the adjacent landmasses (2–4°C). The area of maximum lowering of sea surface temperatures was located only some 5° south of the zone of highest accumulation rates of iceberg‐rafted sands. On land the area of maximum cooling coincided with the zone affected by Mediterranean cyclones. In the eastern part of the ocean, off the European and African coasts the sea surface isotherms diverged northwards and southwards, suggesting that there was a bifurcation in a westerly cold current at the latitude of about Lisbon. All these features are inconsistent with “traditional”; concepts of paleotemperature anomalies associated with astronomically induced climatic changes, but they agree well with the conceptual model of spatial sea surface temperature anomalies caused by massive late‐glacial discharge of icebergs into the ocean.

ISSN:0273-8457    

DOI:10.1080/10889378509377255

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0273-8457    

DOI:10.1080/10889378509377256

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0273-8457    

DOI:10.1080/10889378509377248

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor