Consulta: creatorFacets:"Zahn, R."
Registros recuperados: 7
Data/hora: 13/06/2024 19:27:20

Millennial-scale surface and subsurface paleothermometry from the northeast Atlantic, 55-8 ka BP
Provedor de dados: 5
Autores: Peck, V. L.; Hall, I. R.; Zahn, R.; Elderfield, H.
We present high-resolution records of upper ocean temperatures derived from Mg/Ca ratios of surface-dwelling Globigerina bulloides and subsurface-dwelling Neogloboquadrina pachyderma sinistral and the relative abundance of N. pachyderma sinistral for the period 55-8 ka BP from NE Atlantic sediment core MD01-2461. Millennial-scale temporal variability and longer-term trends in these records enable us to develop a detailed picture of past ocean conditions such as a weakening of thermocline intensity from marine isotope stage 3 (MIS 3) to the last glacial maximum (LGM). The correspondence of all temperature proxies and convergence of paired oxygen isotope (delta O-18) records from both planktonic species implies a breakdown in the thermocline and year-round...
Tipo: Text
Ano: 2008
URL: https://archimer.ifremer.fr/doc/00237/34797/33340.pdf

Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives
Provedor de dados: 5
Autores: Govin, A.; Capron, E.; Tzedakis, P. C.; Verheyden, S.; Ghaleb, B.; Hillaire-marcel, C.; St-onge, G.; Stoner, J. S.; Bassinot, F.; Bazin, L.; Blunier, T.; Combourieu-nebout, N.; El Ouahabi, A.; Genty, D.; Gersonde, R.; Jimenez-amat, P.; Landais, A.; Martrat, B.; Masson-delmotte, V.; Parrenin, F.; Seidenkrantz, M. -s.; Veres, D.; Waelbroeck, C.; Zahn, R.
The Last Interglacial (LIG) represents an invaluable case study to investigate the response of components of the Earth system to global warming. However, the scarcity of absolute age constraints in most archives leads to extensive use of various stratigraphic alignments to different reference chronologies. This feature sets limitations to the accuracy of the stratigraphic assignment of the climatic sequence of events across the globe during the LIG. Here, we review the strengths and limitations of the methods that are commonly used to date or develop chronologies in various climatic archives for the time span (similar to 140 -100 ka) encompassing the penultimate deglaciation, the LIG and the glacial inception. Climatic hypotheses underlying record...
Tipo: Text
Palavras-chave: Last Interglacial; Penultimate deglaciation; Last glacial inception; Chronology; Corals; Speleothems; Ice cores; Marine sediments; Peat and lake sediments; Climate dynamics.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00496/60802/64786.pdf

Past deep-ocean circulation and the paleoclimate record-Gulf of Cadiz
Provedor de dados: 5
Autores: Mulder, T.; Lecroart, T. P.; Voisset, Michel; Schönfeld, J.; Le Drezen, Eliane; Gonthier, E.; Hanquiez, Vincent; Zahn, R.; Faugères, J.-c.; Hernandez-molina, F. J.; Llave-barranco, E.; Gervais, Anne.
Deep marine currents are strongly influenced by climatic changes. They also deposit, rework, and sort sediment, and can generate kilometer-scale sedimentary bodies (drifts). These drifts are made of thoroughly bioturbated, stacked sedimentary sequences called contourites [Gonthier et al., 1984]. As a consequence, change in the direction or intensity of currents can be recorded in the sediments.
Tipo: Text
Ano: 2002
URL: http://archimer.ifremer.fr/doc/00210/32143/30600.pdf

Centennial- to millennial-scale ice-ocean interactions in the subpolar northeast Atlantic 18-41 kyr ago
Provedor de dados: 5
Autores: Hall, I. R.; Colmenero-hidalgo, E.; Zahn, R.; Peck, V. L.; Hemming, S. R.
In order to monitor the evolution of the British-Irish Ice Sheet (BIIS) and its influence in surface ocean structure during marine isotopic stages (MIS) 2 and 3, we have analyzed the sediments recovered in core MD04-2829CQ (Rosemary Bank, north Rockall Trough, northeast Atlantic) dated between similar to 41 and similar to 18 ka B.P. Ice-rafted debris flux and composition, Ar-40/Ar-39 ages of individual hornblende grains, multispecies planktonic stable isotope records, planktonic foraminifera assemblage data and faunal-based sea surface temperatures (SSTs) demonstrate a close interaction between BIIS dynamics and surface ocean structure and water properties in this region. The core location lies beneath the North Atlantic Current (NAC) and is ideal for...
Tipo: Text
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00227/33835/32445.pdf

High-latitude forcing of diatom productivity in the southern Agulhas Plateau during the past 350 kyr
Provedor de dados: 5
Autores: Romero, O. E.; Kim, J. -h.; Barcena, M. A.; Hall, I. R.; Zahn, R.; Schneider, R.
The hydrography of the Indian-Atlantic Ocean gateway has been connected to high-latitude climate dynamics by oceanic and atmospheric teleconnections on orbital and suborbital timescales. A wealth of sedimentary records aiming at reconstructing the late Pleistocene paleoceanography around the southern African continent has been devoted to understanding these linkages. Most of the records are, however, clustered close to the southern South African tip, with comparatively less attention devoted to areas under the direct influence of frontal zones of the Southern Ocean/South Atlantic. Here we present data of the composition and concentration of the diatom assemblage together with bulk biogenic content and the alkenone-based sea surface temperature (SST)...
Tipo: Text
Palavras-chave: Agulhas; SST; Diatoms; Fronts; Silica; Southern Ocean.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00294/40555/39440.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

Salinity changes in the Agulhas leakage area recorded by stable hydrogen isotopes of C-37 alkenones during Termination I and II
Provedor de dados: 5
Autores: Kasper, Sebastian; Van Der Meer, M. T. J.; Mets, A.; Zahn, R.; Damste, J. S. Sinninghe; Schouten, S.
At the southern tip of Africa, the Agulhas Current reflects back into the Indian Ocean causing so-called "Agulhas rings" to spin off and release relatively warm and saline water into the South Atlantic Ocean. Previous reconstructions of the dynamics of the Agulhas Current, based on paleo-sea surface temperature and sea surface salinity proxies, inferred that Agulhas leakage from the Indian Ocean to the South Atlantic was reduced during glacial stages as a consequence of shifted wind fields and a northwards migration of the subtropical front. Subsequently, this might have led to a buildup of warm saline water in the southern Indian Ocean. To investigate this latter hypothesis, we reconstructed sea surface salinity changes using alkenone delta D, and...
Tipo: Text
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00274/38488/36959.pdf