Consulta: subjectFacets:"Heinrich events"
Registros recuperados: 21
Data/hora: 11/06/2024 02:18:07

Catastrophic ice shelf breakup as the source of Heinrich event icebergs
Provedor de dados: 5
Autores: Hulbe, Cl; Macayeal, Dr; Denton, Gh; Kleman, J; Lowell, Tv.
Heinrich layers of the glacial North Atlantic record abrupt widespread iceberg rafting of detrital carbonate and other lithic material at the extreme-cold culminations of Bond climate cycles. Both internal (glaciologic) and external ( climate) forcings have been proposed. Here we suggest an explanation for the iceberg release that encompasses external climate forcing on the basis of a new glaciological process recently witnessed along the Antarctic Peninsula: rapid disintegrations of fringing ice shelves induced by climate-controlled meltwater infilling of surface crevasses. We postulate that peripheral ice shelves, formed along the eastern Canadian seaboard during extreme cold conditions, would be vulnerable to sudden climate-driven disintegration during...
Tipo: Text
Palavras-chave: Heinrich events; Ice shelf disintegration.
Ano: 2004
URL: https://archimer.ifremer.fr/doc/00228/33921/32219.pdf

Heinrich events: hydrological impact
Provedor de dados: 5
Autores: Cortijo, E; Duplessy, Jc; Labeyrie, L; Duprat, J; Paillard, D.
The hydrological impact of the massive iceberg discharges during Heinrich events has been quantified for Heinrich 4 about 37 kyr ago. This event took place in a context of relatively stable orbital forcing and global ice volume. In this article, we propose to quantify the hydrological impact of the Heinrich event 1 which occurred at about 16 kyr BP. This time period is particularly interesting because orbital forcing was strong and it marks the onset of the last deglaciation. The results obtained here show that Heinrich event 1 has a larger isotopic amplitude than Heinrich event 4 when considering the cores located near the melting source. Concerning surface circulation, the northward progression of the North Atlantic Drift is affected only by Heinrich...
Tipo: Text
Palavras-chave: Variabilité climatique rapide; Dernière période glaciaire; Composition isotopique de l’eau; Événements de Heinrich; Rapid climatic variability; Lust glacial periods; Sea water isotopic composition; Heinrich events.
Ano: 2005
URL: https://archimer.ifremer.fr/doc/00232/34322/32714.pdf

Ocean Temperature Variability during the Late Pleistocene
Provedor de dados: 5
Autores: Hoffman, Jeremy Scott.
This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea...
Tipo: Text
Palavras-chave: Paleoclimate; Interglacial; Heinrich events; Deglacial; Paleoceanography; Climate.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00505/61702/65670.pdf

Shoreface migrations at the shelf edge and sea-level changes around the Last Glacial Maximum (Gulf of Lions, NW Mediterranean)
Provedor de dados: 5
Autores: Jouet, Gwenael; Berne, Serge; Rabineau, Marina; Bassetti, Maria-angela; Bernier, P.; Dennielou, Bernard; Sierro, F.j.; Flores, J.a.; Taviani, M.
The Bourcart–Hérault canyon interfluve in the Gulf of Lions (NW Mediterranean) was the site of very high sedimentation (up to 2.5 m/kyr) around the Last Glacial Maximum, due to the vicinity of major fluvial systems that fed the shelf edge. Shoreface deposits and offshore muds deposited during each glacial/interglacial 100 kyr-cycle, created a repeated motif with high-angle and low-angle clinoforms on seismic profiles. New detailed morphological, sedimentological and paleo-environmental data, constrained by 14C dating, allow us to propose a scenario for the evolution of this critical area between 46 and 15 cal. kyr BP. The major seismic sequence (S5), formed as a forced regression during the overall sea-level fall between MIS-3 and MIS-2, can be sub-divided...
Tipo: Text
Palavras-chave: Heinrich events; Western Mediterranean; High resolution sedimentary record; Relative sea level; Last Glacial Maximum.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-2328.pdf

Position of the Polar Front along the western Iberian margin during key cold episodes of the last 45 ka
Provedor de dados: 5
Autores: Eynaud, Frederique; De Abreu, Lucia; Voelker, Antje; Schoenfeld, Joachim; Salgueiro, Emilia; Turon, Jean-louis; Penaud, Aurelie; Toucanne, Samuel; Naughton, Filipa; Goni, Maria Fernanda Sanchez; Malaize, Bruno; Cacho, Isabel.
This paper documents the migration of the Polar Front (PF) over the Iberian margin during some of the cold climatic extremes of the last 45 ka. It is based on a compilation of robust and coherent paleohydrological proxies obtained from eleven cores distributed between 36 and 42 degrees N. Planktonic delta O-18 (Globigerina bulloides), ice-rafted detritus concentrations, and the relative abundance of the polar foraminifera Neogloboquadrina pachyderma sinistral were used to track the PF position. These three data sets, compared from core to core, show a consistent evolution of the sea surface paleohydrology along the Iberian margin over the last 45 ka. We focused on five time slices representative of cold periods under distinct paleoenvironmental forcings:...
Tipo: Text
Palavras-chave: Polar Front; LGM; Heinrich events.
Ano: 2009
URL: https://archimer.ifremer.fr/doc/00218/32909/31415.pdf

Reconstruction of full glacial environments and summer temperatures from Lago della Costa, a refugial site in Northern Italy
Provedor de dados: 5
Autores: Samartin, Stephanie; Heiri, Oliver; Kaltenrieder, Petra; Kühl, Norbert; Tinner, Willy.
Vegetation and climate during the last ice age and the Last Glacial Maximum (LGM, similar to 23,000-19,000 cal BP) were considerably different than during the current interglacial (Holocene). Cold climatic conditions and growing ice-sheets during the last glaciation radically reduced forest extent in Europe to a restricted number of so-called "refugia", mostly located in the southern part of the continent. On the basis of paleobotanical analyses the Euganian Hills (Colli Euganei) in northeastern Italy have previously been proposed as one of the northernmost refugia of temperate trees (e.g. deciduous Quercus, Tilia, Ulmus, Fraxinus excelsior, Acer, Abies alba, Fagus sylvatica, Carpinus and Castanea) in Europe. In this study we provide the first...
Tipo: Text
Palavras-chave: Chironomids; Refugia; Vegetation; Northern Italy; Mediterranean; Climate; Last Glacial; LGM; Heinrich events; Paleoecology; Paleoclimatology.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00421/53234/54773.pdf

Timing of massive ‘Fleuve Manche’ discharges over the last 350 kyr: insights into the European ice-sheet oscillations and the European drainage network from MIS 10 to 2
Provedor de dados: 5
Autores: Toucanne, Samuel; Zaragosi, S.; Bourillet, Jean-francois; Cremer, M.; Eynaud, Frederique; Van Vliet-lanoe, B.; Penaud, A.; Fontanier, C.; Turon, J. L.; Cortijo, E.; Gibbard, P. L.
Continuous high-resolution mass accumulation rates (MAR) and X-ray fluorescence (XRF) measurements from marine sediment records in the Bay of Biscay (NE Atlantic) have allowed the determination of the timing and the amplitude of the ‘Fleuve Manche’ (Channel River) discharges during glacial stages MIS 10, MIS 8, MIS 6 and MIS 4–2. These results have yielded detailed insight into the Middle and Late Pleistocene glaciations in Europe and the drainage network of the western and central European rivers over the last 350 kyr. This study provides clear evidence that the ‘Fleuve Manche’ connected the southern North Sea basin with the Bay of Biscay during each glacial period and reveals that ‘Fleuve Manche’ activity during the glaciations MIS 10 and MIS 8 was...
Tipo: Text
Palavras-chave: Northern north sea; Late weichselian glaciation; Western iberian margin; Abrupt climate change; C 14 YR BP; Deep sea; Heinrich events; Norwegian margin; Millennial scale; English channel.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/00011/12261/9037.pdf

A role for icebergs in the 8.2 ka climate event
Provedor de dados: 5
Autores: Wiersma, Ane P.; Jongma, Jochem I.
We investigate the potential role of icebergs in the 8.2 ka climate event, using a coupled climate model equipped with an iceberg component. First, we evaluate the effect of a large iceberg discharge originating from the decaying Laurentide ice sheet on ocean circulation, compared to a release of an identical volume of freshwater alone. Our results show that, on top of the freshwater effect, a large iceberg discharge facilitates sea-ice growth as a result of lower sea-surface temperatures induced by latent heat of melting. This causes an 8% increased sea-ice cover, 5% stronger reduction in North Atlantic Deep Water production and 1A degrees C lower temperature in Greenland. Second, we use the model to investigate the effect of a hypothetical two-stage lake...
Tipo: Text
Palavras-chave: 8.2 ka event; Climate modeling; Icebergs; Laurentide ice sheet; Hudson Strait; Holocene; Heinrich events.
Ano: 2010
URL: https://archimer.ifremer.fr/doc/00496/60749/65152.pdf

Orbital- and sub-orbital-scale climate impacts on vegetation of the western Mediterranean basin over the last 48,000 yr
Provedor de dados: 5
Autores: Fletcher, William J.; Goni, Maria Fernanda Sanchez.
High-resolution pollen analysis of Alboran Sea Core MD95-2043 provides a 48-ka continuous vegetation record that can be directly correlated with sea surface and deep-water changes. The reliability of this record is supported by comparison with that of Padul (Sierra Nevada, Spain). Marine Isotope Stage (MIS) 3 was characterised by fluctuations in Quercus forest cover in response to Dansgaard-Oeschger climate variability. MIS 2 was characterised by the dominance of semi-desert vegetation. Despite overall dry and cold conditions during MIS 2, Heinrich events (HEs) 2 and 1 were distinguished from the last glacial maximum by more intensely and conditions. Taxon-specific vegetation responses to a tripartite climatic structure within the HEs are observed. In MIS...
Tipo: Text
Palavras-chave: Marine palynology; Land-sea correlation; Iberian margin; Mediterranean region; Dansgaard-Oeschger variability; Heinrich events; LGM; Holocene; Precession.
Ano: 2008
URL: https://archimer.ifremer.fr/doc/00237/34783/33369.pdf

Evidence for an additional Heinrich event between H5 and H6 in the Labrador Sea
Provedor de dados: 5
Autores: Rashid, H; Hesse, R; Piper, Djw.
An additional Heinrich ice-rafting event is identified between Heinrich events 5 and 6 in eight cores from the Labrador Sea and the northwest Atlantic Ocean. It is characterized by sediment rich in detrital carbonate (40% CaCO3) with high concentration of floating dropstones, high coarse-fraction (% &gt; 150 mum) content, and has a sharp contact with the underlying but grades into the overlying hemipelagic sediment. It also shows lighter delta(18)O(Npl) values, indicating freshening due to iceberg rafting and/or meltwater discharge. This event is correlated with Dansgaard-Oeschger event 14 and interpreted as an additional Heinrich event, H5a. The thickness of H5a in the Labrador Sea reaches up to 220 cm. This additional Heinrich event has also been...
Tipo: Text
Palavras-chave: Heinrich events; Nepheloid flow deposits; GISP2; Dansgaard-Oeschger cycle; Labrador Sea.
Ano: 2003
URL: https://archimer.ifremer.fr/doc/00225/33658/32098.pdf

Activity of the turbidite levees of the Celtic-Armorican margin (Bay of Biscay) during the last 30,000 years: Imprints of the last European deglaciation and Heinrich events
Provedor de dados: 5
Autores: Toucanne, Samuel; Zaragosi, S; Bourillet, Jean-francois; Naughton, F; Cremer, M; Eynaud, F; Dennielou, Bernard.
High-resolution sedimentological and micropaleontological studies of several deep-sea cores retrieved from the levees of the Celtic and Armorican turbidite systems (Bay of Biscay - North Atlantic Ocean) allow the detection of the major oscillations of the British-Irish Ice Sheet (BIIS) and 'Fleuve Manche' palaeoriver discharges over the last 30,000 years, which were mainly triggered by climate changes. Between 30 and 20 cal ka, the turbiditic activity on the Celtic-Annorican margin was weak, contrasting with previous stratigraphic models which predicted a substantial increase of sediment supply during low sea-level stands. This low turbidite deposit frequency was most likely the result of a weak activity of the 'Fleuve Manche' palaeoriver and/or of a...
Tipo: Text
Palavras-chave: Turbidites; Heinrich events; LGM; Last deglaciation; Palaeoriver; Fleuve Manche; British irish ice sheet; Bay of Biscay.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-3729.pdf

Varying sediment sources (Hudson Strait, Cumberland Sound, Baffin Bay) to the NW Labrador Sea slope between and during Heinrich events 0 to 4
Provedor de dados: 5
Autores: Andrews, J. T.; Barber, D. C.; Jennings, A. E.; Eberl, D. D.; Maclean, B.; Kirby, M. E.; Stoner, J. S.
Core HU97048-007PC was recovered from the continental Labrador Sea slope at a water depth of 945?m, 250?km seaward from the mouth of Cumberland Sound, and 400?km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from similar to 10 to 58?ka. On-board logging revealed a complex series of lithofacies, including buff-colored detrital carbonate-rich sediments [Heinrich (H)-events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X-ray diffraction on drill-core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the?&lt;?2-mm sediment fraction in a transect of five cores from...
Tipo: Text
Palavras-chave: Baffin Bay; Detrital carbonate (DC-) events; Heinrich events; Labrador Sea; Laurentide Ice Sheet.
Ano: 2012
URL: https://archimer.ifremer.fr/doc/00265/37644/35823.pdf

A 1.2 Ma record of glaciation and fluvial discharge from the West European Atlantic margin
Provedor de dados: 5
Autores: Toucanne, Samuel; Zaragosi, S.; Bourillet, Jean-francois; Gibbard, P. L.; Eynaud, F.; Giraudeau, J.; Turon, J. L.; Cremer, M.; Cortijo, E.; Martinez, P.; Rossignol, L.
The correlation of continental sedimentary records with the marine isotope stratigraphy is a challenge of central importance in Quaternary stratigraphy, particularly in Western Europe where long records of glaciation on land areas are particularly rare. Here we demonstrate for the first time the interrelationship of events during the last 1.2 Ma in an ocean-sediment core from the Bay of Biscay (NE Atlantic), SW of the Channel. The identification of discharge variations from tributary river systems to the 'Fleuve Manche' palaeoriver during glacio-eustatic sea-level lowstands demonstrates the correlation of the marine sediment stratigraphy to the expansion and recession of the European ice-sheets. The amplitude and chronology of European ice-sheet...
Tipo: Text
Palavras-chave: Middle pleistocene transition; Ice sheet dynamics; Sea level; Climate change; North Atlantic; English channel; Heinrich events; Fleuve manche; Deep; Origin.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6956.pdf

Impact of iceberg melting on Mediterranean thermohaline circulation during Heinrich events
Provedor de dados: 5
Autores: Sierro, Fj; Hodell, Da; Curtis, Jh; Flores, Ja; Reguera, I; Colmenero-hidalgo, E; Barcena, Ma; Grimalt, Jo; Cacho, I; Frigola, J; Canals, M.
Down-core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in International Marine Past Global Changes Study (IMAGES) core MD99-2343 in order to study the interactions between climate change in the Northern Hemisphere and the western Mediterranean thermohaline circulation at times of Heinrich events (HE). Our results confirm the antiphase correlation between enhanced North Atlantic Deep Water formation and low ventilation in the Mediterranean. However, this study reveals that this antiphase relationship in deepwater formation between the North Atlantic and Mediterranean was interrupted during times of HE when the injection of large volumes of water from melting icebergs reached the entrance to the Mediterranean....
Tipo: Text
Palavras-chave: Climatic change; Heinrich events; Mediterranean Sea; Carbon and oxygen isotopes; Thermohaline circulation; Pleistocene.
Ano: 2005
URL: https://archimer.ifremer.fr/doc/00232/34354/32759.pdf

Meltwater and ice rafting in the southern Norwegian Sea between 20 and 40 calendar kyr BP: Implications for Fennoscandian Heinrich events
Provedor de dados: 5
Autores: Lekens, W. A. H.; Sejrup, H. P.; Haflidason, H.; Knies, J.; Richter, T.
[ 1] The timing of meltwater release in the southern Norwegian Sea in relation to millennial-scale climate variability is studied from core MD99-2283 based on down-core analysis of stable oxygen and carbon isotopes, calcium carbonate and ice-rafted debris (IRD). Between 20 and 40 calendar (cal) kyr B. P., strong Dansgaard-Oeschger cyclicity is expressed in increased carbonate content and reduced total organic carbon during warm interstadials and IRD marking the end of cold stadials. The planktonic delta(18)O record of core MD99-2283 compared to available isotopic records in the region confirms the existence of multisourced, synchronized meltwater anomalies during Heinrich ( H) events 2 to 4. It was found that the sudden release of meltwater occurs near...
Tipo: Text
Palavras-chave: Meltwater; Nordic Seas; Heinrich events.
Ano: 2006
URL: https://archimer.ifremer.fr/doc/00234/34525/33431.pdf

Heinrich events: Massive late pleistocene detritus layers of the North Atlantic and their global climate imprint
Provedor de dados: 5
Autores: Hemming, Sidney R.
Millennial climate oscillations of the glacial interval are interrupted by extreme events, the so-called Heinrich events of the North Atlantic. Their near-global footprint is a testament to coherent interactions among Earth's atmosphere, oceans, and cryosphere on millennial timescales. Heinrich detritus appears to have been derived from the region around Hudson Strait. It was deposited over approximately 500 +/- 250 years. Several mechanisms have been proposed for the origin of the layers: binge-purge cycle of the Laurentide ice sheet, jokulhlaup activity from a Hudson Bay lake, and an ice shelf buildup/collapse fed by Hudson Strait. To determine the origin of the Heinrich events, I recommend (1) further studies of the timing and duration of the events,...
Tipo: Text
Palavras-chave: Climate; Heinrich layers; Heinrich events; Ice-rafted detritus.
Ano: 2004
URL: https://archimer.ifremer.fr/doc/00224/33549/32033.pdf

Exploring the oxygen isotope fingerprint of Dansgaard-Oeschger variability and Heinrich events
Provedor de dados: 5
Autores: Bagniewski, Witold; Meissner, Katrin J.; Menviel, Laurie.
We present the first transient simulations of Marine Isotope Stage 3 (MIS 3) performed with an oxygen isotope-enabled climate model. Our simulations span several Dansgaard-Oeschger cycles and three Heinrich stadials and are directly compared with oxygen isotope records from 13 sediment and 2 ice cores. Our results are consistent with a 30-50% weakening of the Atlantic Meridional Overturning Circulation during Dansgaard-Oeschger stadials and a complete shutdown during Heinrich stadials. We find that the simulated delta O-18 anomalies differ significantly between Heinrich stadials and non-Heinrich stadials. This difference is mainly due to different responses in ocean circulation, and therefore climate, impacting oceanic delta O-18, while the volume of...
Tipo: Text
Palavras-chave: MIS3; Model-data comparison; Heinrich events; Dansgaard-Oeschger cycles; Delta O-18; AMOC.
Ano: 2017
URL: https://archimer.ifremer.fr/doc/00420/53180/55067.pdf

Hydrographic conditions along the western Iberian margin during marine isotope stage 2
Provedor de dados: 5
Autores: Voelker, A. H. L.; De Abreu, L.; Schoenfeld, J.; Erlenkeuser, H.; Abrantes, F.
The surface water hydrography along the western Iberian margin, as part of the North Atlantic's eastern boundary upwelling system, consists of a complex, seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling. Not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions, such as during marine isotope stage (MIS) 2, and how North Atlantic meltwater events, especially Heinrich events, affected them. To help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western...
Tipo: Text
Palavras-chave: Iberian margin; Last Glacial Maximum; Heinrich events; Planktonic foraminifer; Stable isotopes; Productivity.
Ano: 2009
URL: https://archimer.ifremer.fr/doc/00218/32906/31419.pdf

New insights into upper MOW variability over the last 150 kyr from IODP 339 Site U1386 in the Gulf of Cadiz
Provedor de dados: 5
Autores: Kaboth, Stefanie; Bahr, Andre; Reichart, Gert-jan; Jacobs, Bram; Lourens, Lucas J.
The upper Mediterranean Outflow Water (MOW) paleo-oceanographic history in the Gulf of Cadiz is poorly constrained due to the lack of high-resolution records that pre-date the last glaciation. Existing proxy records concentrate on MOW variability along the middle slope of the Gulf of Cadiz. Here we present a continuous high-resolution benthic foraminifera delta O-18 record from the upper MOW core at IODP Expedition 339 Site U1386 in the Gulf of Cadiz of the past 150,000 years. Based on delta O-18, grain-size and Zr/AI variability comparison of our results with existing Mediterranean Sea (MD01-2472, MD95-2043), open ocean (LR04) and Gulf of Cadiz (MD99-2339) records we have gathered new insights into the evolution of the upper MOW core on glacial...
Tipo: Text
Palavras-chave: Mediterranean outflow; Glacial-interglacial variability; Sapropel; Heinrich events; Gulf of Cadiz.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00421/53235/54767.pdf

Progressive reduction in NE Atlantic intermediate water ventilation prior to Heinrich events: Response to NW European ice sheet instabilities?
Provedor de dados: 5
Autores: Peck, V. L.; Hall, I. R.; Zahn, R.; Scourse, J. D.
We present high-resolution benthic delta C-13 records from intermediate water depth core site MD01-2461 ( 1153 m water depth), from the Porcupine Seabight, NE Atlantic, spanning 43 to 8 kyr B. P. At an average proxy time step of 160 +/- 56 years this core provides information on the linkage between records from the Portuguese Margin and high-latitude North Atlantic basin, allowing additional insights into North Atlantic thermohaline circulation (THC) variability during millennial-scale climatic events of the last glacial. Together, these records document both discrete and progressive reductions in Glacial North Atlantic Intermediate Water (GNAIW) formation preceding Heinrich ( H) events 1, 2, and 4, recorded through the apparent interchange of glacial...
Tipo: Text
Palavras-chave: Atlantic thermohaline circulation; Benthic carbon isotopes; Heinrich events; Meltwater forcing.
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00238/34945/33241.pdf

Modelling abrupt glacial North Atlantic freshening: Rates of change and their implications for Heinrich events
Provedor de dados: 5
Autores: Bigg, Grant R.; Levine, Richard C.; Green, Clare L.
The abrupt delivery of large amounts of freshwater to the North Atlantic in the form of water or icebergs has been thought to lead to significant climate change, including abrupt slowing of the Atlantic Ocean meridional overturning circulation. In this paper we examine intermediate complexity coupled modelling evidence to estimate the rates of change, and recovery, in oceanic climate that would be expected for such events occurring during glacial times from likely sources around the North Atlantic and Arctic periphery. We show that rates of climate change are slower for events with a European or Arctic origin. Palaeoceanographic data are presented to consider, through the model results, the origin and likely strength of major ice-rafting, or Heinrich,...
Tipo: Text
Palavras-chave: Heinrich events; Modelling; Quaternary; Icebergs.
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00227/33777/82665.pdf