摘要:

Glaciers are commonly regarded as sensitive indicators of climatic change, but iceberg calving can partially decouple glacier oscillations from climatic forcing. Recent fluctuations (1942–85) of 72 West Greenland outlet glaciers were studied using aerial photographs, and nine of them examined in the field. Despite similar climatic forcing, variable glacier behaviour is apparent. Eighty‐four percent of the land terminating glaciers have been retreating or stable during the period, whereas more than half the tidewater and lake terminating glaciers have been advancing. The calving glaciers exhibit much greater variability in frontal behaviour. Patterns of change suggest that the land‐terminating glaciers are controlled dominantly by variations in summer temperature, but that calving dynamics have caused the tidewater and lake‐calving glaciers to respond to climatic change in non‐linear ways. Dynamic and response contrasts are apparent between freshwater and tidewater glaciers. Trough geometry is of great significance in controlling the nature and magnitude of frontal change of calving glaciers; in particular, topographic ‘pinning points’ represent potentially stable locations within the fjord at which stillstands almost invariably occur, irrespective of climatic change or re

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00453.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00454.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Since the first studies on the glacial formations of the Jura mountains there have been two concepts concerning type of glaciation and ice origin during the Würmian glaciation. Some authors believed that the Jura was totally inundated by ice of Alpine origin, while others believed that the Jura had its own glaciers, originating from a single ice‐cap. Several recent studies on both the NW and SE slopes of the range define the problem more accurately. This paper presents a synthesis of the new results from mapping the moraine systems and studying the stratigraphic relationships between Alpine and Jura tills. It is concluded that even the highest level of Alpine glaciers could not lead to a penetration of the Jura. A reconstruction of the extension of the Jura glaciers and their relationship with the Alpine glaciers is given, and we conclude that at the Würmian maximum a local ice‐cap was pr

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00455.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00456.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The deposits of six glacial episodes, including five till beds and fluvial deposits of one temperate substage, stratigraphically lying between the Holsteinian and Eemian Interglacials have been recognized in the geological record of the Kleszczów Graben, central Poland. Two other temperate substages have been recognized on the basis of well‐developed weathering horizons on the tills. The depositional environments and general petrological features of these sediments are described and their stratigraphical position is discussed. The Saalian Complex of the Kleszczów Graben has been subdivided into the Older Saalian (three glacial episodes), the Pilica Interstadial and the Younger Saalian (three glacial episodes and two presumed interstadials). This sequence cannot be simply correlated with other Saalian stratigraphic sequences in Europe, although the pre‐Odranian and Odranian (=main Drenthe) tills most probably belong to the Older Saalian, and the Wartanian (Warthe) tills to the Younger Saalian. The geological record presented here suggests that reforestation phases occurred during the Saalian. This contradicts recently developed continental stratigra

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00457.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

At approximately 9200 BP the Romerike area of southeastern Norway was flooded as much asc.35 m by a jøkulhlaup from the ice‐dammed lake ‘Nedre Gl'amsjø’. The flood formed characteristic erosion patterns in the surface of soft sediments and eroded channels in overflow passes. Icebergs driven by the floodwater scoured the bottom and formed imprints on the flooded surface when they were stranded as the waterlevel fell. Information from the eroison features is used to reconstruct the palaeoc

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00458.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Two high resolution pollen records, Caunahue from mid‐latitudes and Harberton from high latitudes, illustrate the issues in defining the Younger Dryas episode in records from southern South America. At mid‐latitudes in the Chilean lake region, previous claims for the existence of a substantially cooler and wetter episode between 11,000 and 10,000 BP can no longer be supported by new pollen records with high temporal and paleoenvironmental resolution, such as Caunahue. The transition from glacial to interglacial conditions occurred in several steps, one shortly after 13,000 BP, when openNothofaguswoodland was replaced by cool‐temperate North Patagonian forest, and one at 9,500 BP, when warmtemperate Validivian forest elements replaced the North Patagonian elements. At high latitudes, on the other hand, high resolution records do show marked short‐term changes during the late‐glacial, inclding the 11,000 to 10,000 BP Interval. However, neither the exact timing nor the duration of these changes is synchronous for specific taxa, neither within one record nor between different records. One of the two intervals of low pollen influx that has been singled out as evidence for a cooler episode is consistently dated between 11,000 and 12,000 BP, while the other interval dates between 10,800 and 9,000 BP. Based on all this information I believe that there is no evidence of Younger Dryas episode for the midlatitudes. For the high latitudes, on the other hand, the overall high paleoenvironmental variability in the records offers multiple choices for a Younger Dryas‐type interval if specific taxa are selected without considering the overall context. However, the lack of synchroneity between short‐term changes of specific taxa between different records suggests primarily a response to local disturbances, rather than a response to a g

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00459.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00460.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Insect analysis was carried out in deposits from a Late Vistulian site at Zabinko, western Poland. Geomorphological, lithostratigraphical and palaeobotanical investigations have been carried out earlier at the same section and published elsewhere. The analysed samples are dated from c. 12,600 to 12,200 BP. A total of 54 insect taxa were determined, the majority being Coleoptera. No major change in the insect fauna during this 400 years period could be detected from the study. The presence of specific phytophagus beetles suggests the same local vegetational environment as reconstructed from the plant macrofossil record, namely a shallow pool with a well‐developed reed vegetation. The pool was situated in an open landscape with scattered trees and herb vegetation. The climatic reconstruction from the insect assemblages suggests a cool temperate climate with an average July temperature of 14–15d̀C, During the same time period arctic/ksubarctic conditionsd, with mean July temperatures of c. 10–12d̀C, prevailed in southernmost Scandinavia. The climatic amelioration in western Poland seems to have started possibl 500 years earlier than in southern

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00461.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00462.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY