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Glacier Advances (glacier + advance)
Selected AbstractsGlacier response in the European Alps to Heinrich Event 1 cooling: the Gschnitz stadial,JOURNAL OF QUATERNARY SCIENCE, Issue 2 2006Susan Ivy-Ochs Abstract The Gschnitz stadial was a period of regionally extensive glacier advance in the European Alps that lies temporally between the breakdown of the Last Glacial Maximum piedmont lobes and the beginning of the Bølling warm interval. Moraines of the Gschnitz stadial are found in medium to small catchments, are steep-walled and blocky, and reflect a snowline lowering of 650,700,m in comparison to the Little Ice Age reference snowline. 10Be surface exposure dating of boulders from the moraine at the type locality at Trins (Gschnitz valley, Tyrol, Austria) shows that it stabilised no later than 15,400,±,1400,yr ago. The overall morphological situation and the long reaction time of the glacier suggest that the climatic downturn lasted about 500,±,300,yr, indicating that the Gschnitz cold period began approximately 15,900,±,1400,yr ago, if not somewhat earlier. This is consistent with published radiocarbon dates that imply that the stadial occurred sometime between 15,400 14C,yr BP (18,020,19,100,cal.,yr) and 13,250 14C,yr BP (15,360,16,015,cal.,yr). A palaeoclimatic interpretation of the Gschnitz glacier based on a simple glacier flow model and statistical glacier-climate models shows that precipitation was about one-third of modern-day precipitation and summer temperatures were about 10,K lower than today. In comparison, during the Younger Dryas, precipitation in this area was only about 10% less and Ts (summer temperature) was only 3.5,4,K lower than modern values. Based on the age of the moraine and the cold and dry climate at that time, we suggest that the Gschnitz stadial was the response of Alpine glaciers to cooling of the North Atlantic Ocean associated with Heinrich Event 1. Copyright © 2005 John Wiley & Sons, Ltd. [source] Calendar year age estimates of Allerød,Younger Dryas sea-level oscillations at Os, western NorwayJOURNAL OF QUATERNARY SCIENCE, Issue 5 2004Øystein S. Lohne Abstract A detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea-level rise was more than 9,m in an area which subsequently experienced an emergence of almost 60,m. The sea-level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time-scale by 14C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post-glacial rise in Betula (birch) pollen). The sea-level curve demonstrates that the Younger Dryas transgression started close to the Allerød,Younger Dryas transition and that the high stand was reached only 200,yr before the Younger Dryas,Holocene boundary. The sea level remained at the high stand for about 300,yr and 100,yr into Holocene it started to fall rapidly. The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice-sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea-level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød,Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd. [source] CHRONOLOGY OF THE LAST GLACIATION IN CENTRAL STRAIT OF MAGELLAN AND BAHÍA INÚTIL, SOUTHERNMOST SOUTH AMERICAGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2005R.D. McCULLOCH ABSTRACT. Glacier fluctuations in the Strait of Magellan tell of the climatic changes that affected southern latitudes at c. 53,55°S during the Last Glacial Maximum (LGM) and Late-glacial/Holocene transition. Here we present a revised chronology based on cosmogenic isotope analysis, 14C assays, amino acid racemisation and tephrochronology. We unpick the effect of bedrock-derived lignite which has affected many 14C dates in the past and synthesise new and revised dates that constrain five glacier advances (A to E). Advance A is prior to the LGM. LGM is represented by Advance B that reached and largely formed the arcuate peninsula Juan Mazia. Carbon-14and 10Be dating show it occurred after 31 250 cal yrs BP and culminated at 25 200,23 100 cal yrs BP and was then followed by the slightly less extensive advance C sometime before 22 400,20 300 cal yrs BP. This pattern of an early maximum is found elsewhere in South America and more widely. Stage D, considerably less extensive, culminated sometime before 17 700,17 600 cal yrs BP and was followed by rapid and widespread glacier retreat. Advance E, which dammed a lake, spanned 15 500,11770 cal yrs BP. This latter advance overlaps the Bølling-Allerød interstadials and the glacier retreat occurs during the peak of the Younger Dryas stadial in the northern hemisphere. However, the stage E advance coincides with the Antarctic Cold Reversal (c. 14800,12700 cal yrs BP) and may indicate that some millennial-scale climatic fluctuations in the Late-glacial period are out of phase between the northern and southern hemispheres. [source] Glacier variations in Breheimen, southern Norway: dating Little Ice Age moraine sequences at seven low-altitude glaciersJOURNAL OF QUATERNARY SCIENCE, Issue 5 2003Stefan Winkler Abstract Moraine sequences in front of seven relatively low-altitude glaciers in the Breheimen region of central southern Norway are described and dated using a ,multi-proxy' approach to moraine stratigraphy. Lichenometric dating, based on the Rhizocarpon subgenus, is used to construct a composite moraine chronology, which indicates eight phases of synchronous moraine formation: AD 1793,1799, 1807,1813, 1845,1852, 1859,1862, 1879,1885, 1897,1898, 1906,1908 and 1931,1933. Although the existence of a few cases of older moraines, possibly dating from earlier in the eighteenth or late in the seventeenth centuries cannot be ruled out by lichenometry, Schmidt hammer R-values from boulders on outermost moraine ridges suggest an absence of Holocene moraines older than the Little Ice Age. Twenty-three radiocarbon dates from buried soils and peat associated with outermost moraines at three glaciers,Tverreggibreen, Storegrovbreen and Greinbreen,also indicate that the ,Little Ice Age' glacier maximum was the Neoglacial maximum at most if not all glaciers. Several maximum age estimates for the Little Ice Age glacier maximum range between the fifteenth and seventeenth centuries, with the youngest from a buried soil being AD 1693. A pre-Little Ice Age maximum cannot be ruled out at Greinbreen, however, where the age of buried peat suggests the outermost moraine dates from AD 981,1399 (at variance with the lichenometric evidence). Glaciofluvial stratigraphy at Tverreggibreen provides evidence for minor glacier advances about AD 655,963 and AD 1277,1396, respectively. Copyright © 2003 John Wiley & Sons, Ltd. [source] Permafrost and Little Ice Age glacier relationships, Posets Massif, Central Pyrenees, SpainPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2004Ralph Lugon Abstract This paper contributes to the study of permafrost in the Pyrenees by reporting geoelectrical investigations and thermal measurement on the Little Ice Age (LIA) forefields of two glaciers. The aim was to assess the internal composition of sedimentary bodies (debris rock glaciers and moraine deposits) located in this proglacial environment. Ground ice was prospected using two DC resistivity techniques: vertical electrical soundings and resistivity mapping at a fixed pseudo-depth. Extreme specific resistivities ranging between 1 and 25,M,,m were detected under a thin (1,2,m) unfrozen layer, indicating the presence of a massive ice layer, certainly buried glacier ice. This ice of glacial origin probably covers former permafrost bodies, i.e. a much thicker layer of perennially frozen sediments. Low subsurface temperatures measured on the deposits indicate that buried glacier ice could have been preserved on top of permafrost since the end of the LIA or earlier Holocene glacier advances. This stratigraphy demonstrates that glaciers and pre-existing perennially frozen sediments (permafrost) were in contact during the LIA. Copyright © 2004 John Wiley & Sons, Ltd. [source] Rhone River flood deposits in Lake Le Bourget: a proxy for Holocene environmental changes in the NW Alps, FranceBOREAS, Issue 4 2005Emmanuel Chapron The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by sub-bottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores. Based on the synthesis of major environmental changes in the NW Alps and on the age-depth model covering the past 7500 years in Lake Le Bourget, periods of enhanced Rhone River flood events in the lake can be related to abrupt climate changes and/or to increasing land use since c. 2700 cal. yr BP. For example, significant land use under rather stable climate conditions during the Roman Empire may be responsible for large flood deposits in the northern part of Lake Le Bourget between AD 966 and 1093. However, during the Little Ice Age (LIA), well-documented major environmental changes in the catchment area essentially resulted from climate change and formed basin-wide major flood deposits in Lake Le Bourget. Up to five ,LIA-like' Holocene cold periods developing enhanced Rhone River flooding activity in Lake Le Bourget are documented at c. 7200, 5200, 2800, 1600 and 200 cal. yr BP. These abrupt climate changes were associated in the NW Alps with Mont Blanc glacier advances, enhanced glaciofluvial regimes and high lake levels. Correlations with European lake level fluctuations and winter precipitation regimes inferred from glacier fluctuations in western Norway suggest that these five Holocene cooling events at 45°N were associated with enhanced westerlies, possibly resulting from a persistent negative mode of the North Atlantic Oscillation. [source] Climate change and ,anomalous' glacier fluctuations: the southwest outlets of Mrdalsjökull, IcelandBOREAS, Issue 2 2004ANDREW F. CASELY Evidence of past glacier fluctuations is valuable palaeoenvironmental data, but determining their relationship to climatic change is sometimes complex because of differing glacier sensitivities and patterns of response. In Iceland, a diverse range of glaciation creates changing geographical patterns of response to climatic changes. The outlet glaciers of the Márdalsjökull ice cap in southern Iceland have produced detailed, but differing, records of change. For a key southwestern sector of the ice cap, we specifically searched for evidence equivalent to the c. 4500 BP, c. 3100 BP and c. 1200 BP advances of Sólheimajökull reported earlier. A combination of geomorphological mapping and dating by tephrochronology and lichenometry was used to constrain the glacier advances and determine the relative magnitude of Neoglacial glacier episodes. This is a key step towards creating a record of the changes for the entire ice cap. Major glacier advances c. 4500,1000 BP previously identified on the southern margin of Márdalsjökull are shown not to have occurred in this sector, where Neoglacial maxima occur post-1755 AD. [source] | ||||||||||