scholarly journals A continuous record of Holocene eolian activity in West Greenland

2003 ◽  
Vol 59 (3) ◽  
pp. 322-334 ◽  
Author(s):  
Nico W. Willemse ◽  
Eduard A. Koster ◽  
Babette Hoogakker ◽  
Frank G.M. van Tatenhove
Keyword(s):  
Greenland Ice Sheet ◽  
Sedimentary Facies ◽  
Two Phase ◽  
Air Masses ◽  
West Greenland ◽  
History Of ◽  
Floodplain Development ◽  
Sand Sheet ◽  
Maritime Air ◽  
Sand Sheets

AbstractEolian landforms are widespread alongside proglacial valley-sandurs in West Greenland and comprise low-relief sand sheets, climbing dunes, and upland loess. Sedimentary facies mainly reflect distance to outwash-source zones and the influence of vegetation cover. The sediments show stratification types typical for poorly to moderately vegetated sand-sheets, alternately laminated silt/peat sequences, and unstratified loess. Twenty-five accelerator mass spectrometry 14C dates provide the basis for the chronostratigraphy of the inland eolian deposits. 14C dates from interstratified sand-sheets suggest that the bulk of eolian sands were deposited prior to 3400 cal yr B.P. and after 550 cal yr B.P. This two-phase formation for the inland dunes most likely reflects local changes in proglacial floodplain development and meltwater rerouting associated with a significant recession of the Greenland ice sheet during the mid Holocene climate optimum. Subsequent floodplain regeneration and renewed sand-sheet formation after 550 cal yr B.P. followed when the ice margin readvanced to its present position. In contrast, atmospheric deposition of regionally derived silt in upland peat mires has been continuous since at least 4750 cal yr B.P. Silt influx data demonstrate a strongly episodic history of the intensity of eolian activity over the past five millennia, which tentatively reflects alternating periods of (winter) aridity associated with the variable incursion of maritime air masses over the interior ice-free areas of West Greenland.

Greenland Ice Sheet History Since the Last Glaciation

1974 ◽  
Vol 4 (4) ◽  
pp. 429-440 ◽  
Author(s):  
Norman W. Ten Brink ◽  
Anker Weidick
Keyword(s):  
Average Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Large Area ◽  
West Greenland ◽  
Last Glaciation ◽  
History Of ◽  
Inland Ice

The position of the Inland Ice margin during the late Wisconsin-Würm glaciation (ca. 15,000 yr BP) is probably marked by offshore banks (submarine moraines?) in the Davis Strait. The history of the Inland Ice since the late Wisconsin-Würm can be divided into four principal phases: (1) Relatively slow retreat from the offshore banks occurred at an average rate of approximately 1 km/100 yr until ca. 10,000 yr BP (Younger Dryas?) when the Taserqat moraine system was formed by a readvance. (2) At ca. 9500 yr BP, the rate of retreat increased markedly to about 3 km/100 yr, and although nearly 100 km of retreat occurred by ca. 6500 yr BP, it was punctuated by frequent regional reexpansions of the Inland Ice that formed extensive moraine systems at ca. 8800-8700 yr BP (Avatdleq-Sarfartôq moraines), 8400-8100 yr BP (Angujârtorfik-Fjord moraines), 7300 yr BP (Umîvît moraines), and 7200-6500 yr BP (Keglen-Mt, Keglen moraines). (3) Between 6500 and 700 yr BP, discontinous ice-margin deposits and ice-disintegration features were formed during retreat, which may have continued until the ice margin was near or behind its present position by ca. 6000 yr BP. Most of the discontinuous ice-margin deposits occur within 5–10 km of the present ice margin, and may have been formed by two main phases of readvance at ca. 4800-4000 yr BP and 2500-2000 yr BP. (4) Since a readvance at ca. 700 yr BP, the Inland Ice margin has undergone several minor retreats and readvances resulting in deposition of numerous closely spaced moraines within about 3 km of the present ice margin. The young moraines are difficult to correlate regionally, but several individual moraines have the following approximate ages: A.D. 1650, 1750, and 1880–1920.Inland Ice fluctuations in West Greenland were very closely paralleled by Holocene glacial events in East Greenland and the eastern Canadian Arctic. Such similarity of glacier behavior over a large area strongly suggests that widespread climatic change was the direct cause of Holocene glacial fluctuations. Moreover, historical advances of the Inland Ice margin followed slight temperature decreases by no more than a few decades, and 18O data from Greenland ice cores show that slight temperature decreases occurred frequently throughout the Holocene. Therefore, we conclude that construction of the major Holocene moraine systems in West Greenland was caused by slight temperature decreases, which decreased rates of ablation and thereby produced practically immediate advances of the ice sheet margin, but did not necessarily affect the long-term equilibrium of the ice sheet.

scholarly journals Early Holocene history of the west Greenland Ice Sheet and the GH-8.2 event

2006 ◽  
Vol 25 (9-10) ◽  
pp. 904-922 ◽  
Author(s):  
A.J. Long ◽  
D.H. Roberts ◽  
S. Dawson
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
The West ◽  
West Greenland ◽  
History Of

scholarly journals Topographic and Glaciological Controls on Holocene Ice-Sheet Margin Dynamics. Central West Greenland

1990 ◽  
Vol 14 ◽  
pp. 307-310 ◽  
Author(s):  
C.R. Warren ◽  
N.R.J. Hulton
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacial Maximum ◽  
Warm Climate ◽  
Short Term ◽  
The West ◽  
West Greenland ◽  
The Past

The retreat of the West Greenland ice sheet from its Sisimiut (Wisconsinan) glacial maximum, was punctuated by a series of Stillstands or small readvances that formed numerous moraines. These landforms have been interpreted in the past as the result of short-term, regional falls in ablation-season temperatures. However, mapping of the geomorphological evidence south of Ilulissat (Jakobshavn) suggests that retreat behaviour was not primarily governed by climate, and therefore that the former ice margins are not palaeoclimatically significant. During warm climate ice-sheet wastage, the successive quasi-stable positions adopted by the ice margin were largely governed by topography. The retreat of the inherently unstable calving glaciers was arrested only at topographically-determined locations where stability could be achieved.

The significance of the boundary between the Rhoscolyn and New Harbour formations on Holy Island, North Wales, to the deformation history of Anglesey

2012 ◽  
Vol 150 (3) ◽  
pp. 519-535 ◽  
Author(s):  
JACK E. TREAGUS ◽  
SUSAN H. TREAGUS ◽  
NIGEL H. WOODCOCK
Keyword(s):  
Lower Cambrian ◽  
Depositional Environment ◽  
High Strain ◽  
The Other ◽  
Deformation History ◽  
Two Phase ◽  
Phase Deformation ◽  
North Wales ◽  
History Of ◽  
Tectonic Features

AbstractThe boundary between the Rhoscolyn and New Harbour formations on Holy Island, Anglesey, has been described as a high strain zone or as a thrust. The boundary is here described at four localities, with reference to the contrasting sedimentary and deformational character of the two formations. At one of these localities, Borth Wen, sandstones and conglomerates at the top of the Rhoscolyn Formation are followed, without any break, by tuffs and then mudstones of the New Harbour Formation. It is concluded that there is clear evidence of depositional continuity across the boundary here, and that both formations subsequently shared a common two-phase deformation. The first (D1) was manifestly different in intensity and scale in the two formations, whereas the second (D2) produced very similar structures in both. The other three localities provide continuity of sedimentary and tectonic features at this boundary in a traverse along the length of Holy Island, leading us to identify two previously unrecognized major D1 folds in addition to the Rhoscolyn Anticline. At one of these localities (Holyhead), we confirm the presence of Skolithos just below the boundary, supporting radiometric evidence for a lower Cambrian or later age for the Rhoscolyn Formation. A turbidite interpretation for both the Rhoscolyn and New Harbour formations best fits the available evidence. A deep-water depositional environment is still compatible with the sporadic presence of Skolithos burrows, but less so with reported observations of hummocky and swaley cross-stratification lower down the South Stack Group.

Carboniferous-Triassic gastropod diversity patterns and the Permo-Triassic mass extinction

Paleobiology ◽  
1990 ◽  
Vol 16 (2) ◽  
pp. 187-203 ◽  
Author(s):  
Douglas H. Erwin
Keyword(s):  
Mass Extinction ◽  
Detrended Correspondence Analysis ◽  
Taxonomic Composition ◽  
Late Paleozoic ◽  
Lower Permian ◽  
Two Phase ◽  
Environmental Distribution ◽  
Extinction Rates ◽  
History Of ◽  
Permian Mass Extinction

Paleozoic and post-Paleozoic marine faunas are strikingly different in composition. Paleozoic marine gastropods may be divided into archaic and modern groups based on taxonomic composition, ecological role, and morphology. Paleozoic assemblages were dominated by pleurotomariids (Eotomariidae and Phymatopleuridae), the Pseudozygopleuridae, and, to a lesser extent, the Euomphalidae, while Triassic assemblages were dominated by the Trochiina, Amberleyacea, and new groups of Loxonematoidea and Pleurotomariina. Several new groups of caenogastropods appeared as well. Yet the importance of the end-Permian mass extinction in generating these changes has been questioned. As part of a study of the diversity history of upper Paleozoic and Triassic gastropods, to test the extent to which taxonomic and morphologic trends established in the late Paleozoic are continued after the extinction, and to determine the patterns of selectivity operating during the extinction, I assembled generic and morphologic diversity data for 396 genera in 75 families from the Famennian through the Norian stages. Within this interval, gastropod genera underwent an adaptive radiation during the Visean and Namurian, largely of pleurotomariids, a subsequent period of dynamic stability through the Leonardian, a broad-based decline during the end-Permian mass extinction, and a two-phase post-extinction rebound during the Triassic. The patterns of generic diversity within superfamily-level clades were analyzed using Q-mode factor analysis and detrended correspondence analysis.The results demonstrate that taxonomic affinity, previous clade history, generic age, and gross morphology did not determine survival probability of genera during the end-Permian extinction, with the exception of the bellerophontids, nor did increasing diversity within clades or expansion of particular morphologies prior to the extinction facilitate survival during the extinction or success after it. The pleurotomariids diversified during the Lower Permian, but were heavily hit by the extinction. Similarly, trochiform and turriculate morphologies, among those which Vermeij (1987) has identified as having increased predation resistance, were expanding in the late Paleozoic, but suffered similar extinction rates to other nondiversifying clades. Survival was a consequence of broad geographic and environmental distribution, as was the case during background periods.

scholarly journals Holocene shore-lines and glacial stages in Greenland - an attempt at correlation

1972 ◽  
Vol 41 ◽  
pp. 1-39
Author(s):  
A Weidick
Keyword(s):  
North America ◽  
Current Literature ◽  
Younger Dryas ◽  
Low Pressure ◽  
East Greenland ◽  
West Greenland ◽  
History Of ◽  
Climatic Optimum ◽  
North Greenland

Post-Wisconsinian uplift of West, North and East Greenland has been estimated on the basis of information in current literature and compared to the data collected by the author in central West Greenland. For West and North Greenland the dated uplift allows an estimate to be made of the age of former shore-lines, which in turn have been used to date the stages of the extent of the Inland lce. The results have been compared with published information on the age of glacial stages in East Greenland. The estimated ages of the ice margin stages imply a history of deglaciation in West (and North?) Greenland comparable to that of North America. In both areas the major deglaciation took place after the Younger Dryas and a marked halt took place in Boreal times. It is possibie that the history of East Greenland is more closely related to that of Scandinavia where a widespread deglaciation took place prior to the Younger Dryas. The deglaciation of North Greenland was interrupted by a marked readvance or readvances during the climatic optimum. It is possible that the northward shift of the low pressure centres during this period led to an increased accumulation on the northern part of the Inland lce.

scholarly journals Firn temperature and meltwater refreezing in the lower accumulation area of the Greenland ice sheet, Pâkitsoq, West Greenland

1993 ◽  
Vol 159 ◽  
pp. 109-114
Author(s):  
R.J Braithwaite
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
International Project ◽  
Sea Level Changes ◽  
West Greenland ◽  
Degree Day ◽  
Air Temperatures ◽  
Surface Melt ◽  
High Degree

Firn temperatures and meltwater refreezing are studied in the lower accumulation area of the Greenland ice sheet as part of an international project on sea level changes. In the study area, 1440–1620 m a.s.l., meltwater penetrates several metres into the firn and refreezes, warming the firn by 5–7°C compared with annual air temperatures. This firn warming is closely related to surface melt which can be estimated by several methods. A relatively high degree-day factor is needed to account for the melt rates found.

scholarly journals Assessing ice margin fluctuations on differing timescales: Chronological constraints from Sermeq Kujatdleq and Nordenskiöld Gletscher, central West Greenland

The Holocene ◽  
2018 ◽  
Vol 28 (7) ◽  
pp. 1160-1172 ◽  
Author(s):  
Samuel E Kelley ◽  
Jason P Briner ◽  
Sandy L O’Hara
Keyword(s):  
Late Holocene ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Dynamics ◽  
West Greenland ◽  
Southern Site ◽  
Ice Velocity ◽  
Observational Record ◽  
Local Variability

The observational record of ice margin position reveals asynchrony in both the timing and magnitude of Greenland Ice Sheet (GrIS) margin fluctuations and illustrates the complex reactions of ice sheets to climatic perturbations. In this study, we reconstruct the timing and pattern of middle- and late-Holocene GrIS margin fluctuations at two locations, ~190 km apart, in central West Greenland using radiocarbon-dated sediment cores from proglacial-threshold lakes. Our results demonstrate that deglaciation occurs at both sites during the early Holocene, with the ice sheet remaining in a smaller-than-present ice margin configuration until ~500 years ago when it readvanced into lake catchments at both sites. At our northern site, Sermeq Kujatdleq, the late-Holocene advance of the GrIS approached maximum position during the past 280 years, with the culmination of the advance occurring at AD 1992–1994, and modern retreat was underway by AD 1998–2001. In contrast, field and observational evidence suggest that the GrIS at our southern site, Nordenskiöld Gletscher, has been advancing or stable throughout the 20th century. These results, in conjunction with previous work in the region, highlight the asynchronous nature of late-Holocene advances and subsequent modern retreat, implying that local variability, such as ice velocity or ice dynamics, is responsible for modulating ice margin response to changes in climate on these decadal to centennial timescales. Additional high-resolution records of past ice sheet fluctuations are needed to inform and more accurately constrain our predictions of future cryosphere response to changes in climate.

NEUTRALIZING ANTIBODIES AGAINST MOUSE-ADAPTED LANSING STRAIN OF POLIOMYELITIS VIRUS IN THE SERA OF ACUTE AND CONVALESCENT CASES AND NORMAL INDIVIDUALS

1950 ◽  
Vol 28e (2) ◽  
pp. 34-40
Author(s):  
E. L. Barton ◽  
N. A. Labzoffsky ◽  
W. G. Ross ◽  
L. P. Morrissey
Keyword(s):  
British Columbia ◽  
Neutralizing Antibodies ◽  
Acute Stage ◽  
Present Communication ◽  
Two Phase ◽  
Poliomyelitis Virus ◽  
Normal Individuals ◽  
History Of

The present communication deals with a survey of neutralizing antibodies to mouse-adapted Lansing strain of poliomyelitis virus in the sera of acute, convalescent, and normal individuals during a 1946 epidemic. Two-phase sera were obtained from residents of Ontario and British Columbia and convalescent and normal sera from Quebec. In the sera of 17 out of 35 Ontario patients neutralizing antibodies were demonstrable during the acute stage. In four of these seropositive individuals, there was an increase in the neutralizing titer during convalescence and in three patients there was a notable drop in the titer. The remaining 18 patients were found to be seronegative during both the acute and convalescent stages. Sera from six out of nine British Columbia patients, likewise contained neutralizing antibodies to the Lansing strain of virus during the acute stage. In four of these the titer remained unchanged during convalescence, in one the titer decreased, and another patient became seronegative. Of the remaining three, two continued to be seronegative and one became seropositive during convalescence. Positive neutralization reactions were obtained with 17 out of 44 convalescent sera from Ontario and 62 out of 146 convalescent sera from Quebec Sera from 51 children without history of poliomyelitis and 100 adult sera taken at random from specimens submitted for Wassermann tests were obtained from Quebec. Of the children's sera 43%, and of the adults’, 48%, contained neutralizing antibodies. The results obtained closely agree with those reported by American workers.

scholarly journals Multi-method observation and analysis of an impulse wave and tsunami caused by glacier calving

2015 ◽  
Vol 9 (6) ◽  
pp. 6471-6493 ◽  
Author(s):  
M. P. Lüthi ◽  
A. Vieli
Keyword(s):  
Tsunami Wave ◽  
Tide Gauge ◽  
Impulse Wave ◽  
West Greenland ◽  
Tsunami Waves ◽  
The Future ◽  
History Of ◽  
Impulse Waves ◽  
Run Up

Abstract. Glacier calving can cause violent impulse waves which, upon landfall, can lead to destructive tsunami-like waves. Here we present data acquired during a calving event from Eqip Sermia, an ocean-terminating glacier in West Greenland. During an exceptionally well documented event, the collapse of 9 × 105 m3 ice from a 200 m high ice cliff caused an impulse wave of 50 m height, traveling at a speed of 25–30 m s-1. This wave was filmed from a tour boat in 800 m distance from the calving face, and simultaneously measured with a terrestrial radar interferometer and a tide gauge. Tsunami wave run-up height on the steep opposite shore in 4 km distance was 10–15 m, destroying infrastructure and eroding old vegetation. These observations indicate that such high tsunami waves are a recent phenomenon in the history of this glacier. Analysis of the data shows that only moderately bigger tsunami waves are to be expected in the future, even under rather extreme scenarios.

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