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| Registros recuperados: 105 | |
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| Bauch, Henning A.; Erlenkeuser, Helmut. |
| Sediment cores from the Norwegian Sea were studied to evaluate interglacial climate conditions of the marine isotope stage 5e (MIS 5e). Using planktic forminiferal assemblages as the core method, a detailed picture of the evolution of surface water conditions was derived. According to our age model, a step-like deglaciation of the Saalian ice sheets is noted between ca. 135 and 124.5 Kya, but the deglaciation shows little response with regard to surface ocean warming. From then on, the rapidly increasing abundance of subpolar forminifers, concomitant with decreasing iceberg indicators, provides evidence for the development of interglacial conditions sensu stricto (5e-ss), a period that lasted for about 9 Ky. As interpreted from the foraminiferal records,... |
| Tipo: Text |
Palavras-chave: Holocene; Last interglacial; Nordic seas; Palaeoceanography; Planktic foraminifers; Stable isotopes. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34811/33316.pdf |
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| Risebrobakken, B; Jansen, E; Andersson, C; Mjelde, E; Hevroy, K. |
| High-resolution records from IMAGES core MD95-2011 in the eastern Norwegian Sea provide evidence for relatively large- and small-scale high-latitude climate variability throughout the Holocene. During the early and mid-Holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of Arctic intermediate and near-surface waters. For the late Holocene a relaxation of the atmospheric forcing resulted in increased influence of Atlantic water. The main changes in Holocene climate show no obvious connection to changing solar irradiance, and spectral analysis reveals no consistent signature for any periodic behavior of Holocene climate at millennial or centennial timescales. There are, however, indications of consistent... |
| Tipo: Text |
Palavras-chave: Holocene; Climate; Nordic Seas; NAO; High resolution; Variability. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00224/33500/32119.pdf |
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| Kienast, M.; Lehmann, M. F.; Timmermann, A.; Galbraith, E.; Bolliet, T.; Holboum, A.; Normandeau, C.; Laj, C.. |
| Sedimentary delta(15)N records from the oligotrophic western equatorial Pacific (WEP) off Mindanao show that late Holocene sedimentary delta(15)N is substantially lower than that of the early Holocene, following a gradual >3 parts per thousand decrease that occurred between 7 and 3 kyrs ago. Analyses of modem day nitrate isotope profiles from the same region indicate the sensitivity of the WEP N pools towards (1) the advection of (15)N-enriched nitrate from the Eastern Equatorial Pacific (EEP) by the North Equatorial Current (NEC) and the Mindanao Current in subsurface waters and, (2) at shallow depths, the input of new and (15)N-depleted nitrate through N, fixation. We suggest that the Holocene decrease in sedimentary delta(15)N reflects a diminished... |
| Tipo: Text |
Palavras-chave: Tropical Pacific; El Nino; Surface temperature; Fresh water; Nitrate; Mindanao; Ocean; Variability; Holocene; Seawater. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00207/31843/30257.pdf |
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| Railsback, L. Bruce; Brook, George A.; Liang, Fuyuan; Marais, Eugene; Cheng, Hai; Edwards, R. Lawrence. |
| Stalagmite Orum-1 from a cave near Orumana in northwestern Namibia provides a multi-proxy record of regional drying with increasing global-scale warmth over the last 47 kyr, in a region with few long well-dated location specific paleoclimate records. Data from Stalagmite Orum-1 include carbon and oxygen stable isotope ratios, proportions of aragonite and calcite, pronouncedly differing petrographic fabrics, positions of layer-bounding surfaces, variation in layer-specific width, and changes in layer thickness, all of which combine to support change from wetter to drier conditions. Combined with fourteen U-Th ages, they suggest that climate was wetter in northwestern Namibia during globally cold MIS 3 than it is today, and with more grass than is present... |
| Tipo: Text |
Palavras-chave: Namibia; Paleoclimate; Pleistocene; Holocene; Savanna; Stalagmite. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53213/54862.pdf |
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| Penaud, Aurélie; Ganne, Axelle; Coste, Pierre-olivier; Herlédan, Maïwenn; Durand, Matthieu; Mojtahid, Meryem; Nizou, Jean; Toucanne, Samuel. |
| The high-time resolution (∼70 years in average) multi-proxy analysis conducted on the midshelf core CBT-CS11 (47°46.429’N; 4°25.308’W; 73m depth; 3.96 m long; NW France, S Brittany) revealed the complexity of the palaeohydrological and palaeoclimatic signals recorded over the last 7 kyrs in the recently published paper: “Oceanic versus continental influences over the last 7 kyrs from a midshelf record in the northern Bay of Biscay (NE Atlantic)” [1]. This study presents the whole CBT-CS11 dataset discussed in [1] including sedimentological (XRF and grain-size (total from [1] and CaCO3-free from [2]) analyses), geochemical (oxygen and carbon stable isotopes on two different benthic foraminiferal species: Ammonia falsobeccarii from [1] and Cibicides... |
| Tipo: Text |
Palavras-chave: Holocene; NE Atlantic Ocean; Pollen assemblages; Dinoflagellate cyst assemblages; Stable isotopes; Grain-size analysis; XRF. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00610/72209/71003.pdf |
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| Stoner, Joseph S.; Jennings, Anne; Kristjansdottir, Greta B.; Dunhill, Gita; Andrews, John T.; Hardardottir, Jorunn. |
| We report the intercalibration of paleomagnetic secular variation (PSV) and radiocarbon dates of two expanded postglacial sediment cores from geographically proximal, but oceanographically and sedimentologically contrasting settings. The objective is to improve relative correlation and chronology over what can be achieved with either method alone. Core MD99-2269 was taken from the Hunafloaall Trough on the north Iceland shelf. Core MD99-2322 was collected from the Kangerlussuaq Trough on the east Greenland margin. Both cores are well dated, with 27 and 20 accelerator mass spectrometry (14)C dates for cores 2269 and 2322, respectively. Paleomagnetic measurements made on u channel samples document a strong, stable, single-component magnetization. The... |
| Tipo: Text |
Palavras-chave: Holocene; Paleomagnetic secular variation; Radiocarbon dating. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00233/34436/32934.pdf |
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| LESSA,GUILHERME C.; BITTENCOURT,ABÍLIO C.S.P.; BRICHTA,ARNO; DOMINGUEZ,JOSÉ M. L.. |
| Todos os Santos Bay is a large (<img ALIGN="BOTTOM" BORDER="0" SRC="http:/img/fbpe/aabc/v72n4/0052img1.gif" ALT="$ \approx$"> 1000 km²), structurally controlled tidal bay in northeast Brazil. Three main drainage basins debouch into the bay, providing a mean freshwater discharge of 200 m³/s (prior to 1985), or less than 1% of the spring tidal discharge through the bay mouth. Based on the result of several sedimentological studies performed in the 1970's, five surface sedimentary facies were identified inside the bay, namely i) transgressive siliciclastic marine sand facies; ii) transgressive bay sand-mud facies; iii) a transgressive carbonate marine sand facies; iv) regressive bay-mud facies, and v) regressive fluvial sand facies. The spatial... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Estuary; Sediment; Stratigraphy; Holocene. |
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400008 |
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| 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 |
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| Saikku, Reetta Maaria. |
| In Project I, Western tropical Pacific sea surface temperatures and Pacific Deep Water temperatures during Marine Isotope Stage 3 have been reconstructed from the δ18O and Mg/Ca of planktonic and benthic foraminifera from Marion Dufresne core MD98-2181. This 36m marine core was collected at 6.3°N from a water depth of 2114m. With sediment accumulation rates of up to 80cm/ky, it provides a decadally-resolved history of ocean variability during the last glacial period. Surface temperatures and salinities at this site varied in close association with millennial-scale atmospheric temperature swings at high northern latitudes as reflected in the GISP2 ice core. At times of colder atmospheric temperatures over Greenland, the western Pacific was more saline and... |
| Tipo: Text |
Palavras-chave: Climate; Pacific; Tropical; Glacial; Holocene. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00495/60653/64150.pdf |
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| Manighetti, B; Palmer, A; Eden, D; Elliot, M. |
| We identify c. 7000 cal yr BP Tuhua Tephra in a marine sediment core from offshore eastern North Island, New Zealand. Its mineral assemblage includes aegirine, which is diagnostic for the Tuhua (Mayor Island) Volcanic Centre, and electron microprobe analyses of glass shards yield compositions close to published analyses of the tephra onshore, closer to the source. Associated radiocarbon ages on planktonic foraminifera from the core show that its age lies within the range previously determined for the caldera-forming event that generated Tuhua Tephra. This occurrence, >380 km southeast of the source, indicates that the dispersal of the ash was bi-directional, and that earlier estimates of this tephra's volume may be conservative. |
| Tipo: Text |
Palavras-chave: Mayor Island; Tephrochronology; Holocene; Tuhua Tephra; Isopach. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00225/33656/32097.pdf |
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| Mairesse, Aurélien. |
| The study of past climates and of mechanisms that have influenced their evolution is the key to anticipate the future climate changes. This doctoral thesis focusses on the Holocene climate, the ongoing interglacial, that starts about 11,700 years ago. The current paleoclimate knowledge is based on the one hand, on the climate models results and, on the other hand, on the reconstruction of physical variables derived from climate archives as the ice cores, the marine cores or the pollens for instance. These two types of information are complementary. Here we have combined them to obtain reconstructions of past climates using data assimilation. This technique is standard in many disciplines but not yet in paleoclimatology. The data assimilation method applied... |
| Tipo: Text |
Palavras-chave: Climate; Data assimilation; Paleoclimate; Holocene; LOVECLIM model; Proxy record. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00506/61719/65687.pdf |
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| Khider, D.; Jackson, C. S.; Stott, L. D.. |
| We investigate the relationship between tropical Pacific and Southern Ocean variability during the Holocene using the stable oxygen isotope and magnesium/calcium records of cooccurring planktonic and benthic foraminifera from a marine sediment core collected in the western equatorial Pacific. The planktonic record exhibits millennial-scale sea surface temperature (SST) oscillations over the Holocene of ~0.5°C while the benthic δ18Oc document ~0.10‰ millennial-scale changes of Upper Circumpolar Deep Water (UCDW), a water mass which outcrops in the Southern Ocean. Solar forcing as an explanation for millennial-scale SST variability requires (1) a large climate sensitivity and (2) a long 400 year delayed response, suggesting that if solar forcing is the cause... |
| Tipo: Text |
Palavras-chave: Holocene; Millennial-scale variability; Mg; Ca thermometry; Uncertainty Quantification; Solar Forcing. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40166/39058.pdf |
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| Zielhofer, Christoph; Fletcher, William J.; Mischke, Steffen; De Batist, Marc; Campbell, Jennifer F. E.; Joannin, Sebastien; Tjallingii, Rik; El Hamouti, Najib; Junginger, Annett; Stele, Andreas; Bussmann, Jens; Schneider, Birgit; Lauer, Tobias; Spitzer, Katrin; Strupler, Michael; Brachert, Thomas; Mikdad, Abdeslam. |
| The limited availability of high-resolution continuous archives, insufficient chronological control, and complex hydro-climatic forcing mechanisms lead to many uncertainties in palaeo-hydrological reconstructions for the Western Mediterranean. In this study we present a newly recovered 19.63 m long core from Lake Sidi Ali in the North African Middle Atlas, a transition zone of Atlantic, Western Mediterranean and Saharan air mass trajectories. With a multi-proxy approach based on magnetic susceptibility, carbonate and total organic C content: core-scanning and quantitative XRF, stable isotopes of ostracod shells, charcoal counts, Cedrus pollen abundance, and a first set of diatom data, we reconstruct Western Mediterranean hydro-climatic variability,... |
| Tipo: Text |
Palavras-chave: Holocene; Younger Dryas; Winter rain minima; Atlantic forcing; Western Mediterranean; North Atlantic Oscillation (NAO); Seasonality; Solar forcing; Lake sediments; Middle Atlas; Morocco. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00420/53188/55016.pdf |
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| Hesp,Patrick A.; Dillenburg,Sergio R.; Barboza,Eduardo G.; Tomazelli,Luiz J.; Ayup-Zouain,Ricardo N.; Esteves,Luciana S.; Gruber,Nelson L.S.; Toldo-Jr.,Elirio E.; Tabajara,Luiz L.C. de A.; Clerot,Luiz C.P.. |
| Many prograded barriers and some dunefields in theworld have been termed 'beach ridge' plains, but the actual genesis of the 'ridges' is often unknown. Use of the terms, berms, beach ridges and foredunes is also confusing in the literature because their definitions are highly variable and are commonly used interchangeably. Thus, the formation and definition of sand berms, beach ridges and foredunes is briefly reviewed. Beach ridges are re-defined as entirely wave formed deposits which are most commonly formed during high wave conditions and/or elevated water levels (e.g. storm surges). Foredunes are formed by aeolian sand deposition in vegetation on the backshore. Some dunefields in Brazil have been called beach ridge plains when they are, in fact,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Beach ridges; Coastal barriers; Transgressive dunefields; Holocene; Southern Brazil. |
| Ano: 2005 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652005000300010 |
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| Guerra,Núbia C.; Kiang,Chang H.; Sial,Alcides N.. |
| Holocene beachrocks of the Jaguaribe beach, State of Pernambuco, northeastern Brazil, consist of horizontal, cemented layers approximately 40 cm thick. The cement shows three textural varieties: (a) calciferous, surrounding siliciclastic grains, (b) micritic, with an acicular fringe; and (c) cryptocrystalline calcite in pores. Early cementation took place at the water table below beach ridges, where geochemical, hydrodynamic and, perhaps, also microbiological conditions favored rapid precipitation of aragonite and/or high-Mg calcite. delta13C values range from -1.8 to +1.5 for dissolved carbonate in interstitial water and from +0.2 to +2.1 for bioclastic components. delta18O values range from -2.8 to +0.5 for seawater, freshwater and interstitial water.... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Beachrocks; Early diagenesis; O and C isotopes; Holocene. |
| Ano: 2005 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652005000200011 |
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| Registros recuperados: 105 | |
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