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| Brandefelt, J.; Kjellstrom, E.; Naslund, J. -o.; Strandberg, G.; Voelker, A. H. L.; Wohlfarth, B.. |
| We present a coupled global climate model (CGCM) simulation, integrated for 1500 yr to quasi-equilibrium, of a stadial (cold period) within Marine Isotope Stage 3 (MIS 3). The simulated Greenland stadial 12 (GS12; similar to 44 ka BP) annual global mean surface temperature (T-s) is 5.5 degrees C lower than in the simulated recent past (RP) climate and 1.3 degrees C higher than in the simulated Last Glacial Maximum (LGM; 21 ka BP) climate. The simulated GS12 is evaluated against proxy data and previous modelling studies of MIS3 stadial climate. We show that the simulated MIS 3 climate, and hence conclusions drawn regarding the dynamics of this climate, is highly model-dependent. The main findings are: (i) Proxy sea surface temperatures (SSTs) are higher... |
| Tipo: Text |
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| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00228/33898/32218.pdf |
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| Amore, F. O.; Flores, J. A.; Voelker, A. H. L.; Lebreiro, S. M.; Palumbo, E.; Sierro, F. J.. |
| Changes in paleoclimate and paleoproductivity patterns have been identified by analysing, in conjunction with other available proxy data, the coccolithophore assemblages from core MD03-2699, located in the Portuguese margin in the time interval from the Marine Isotope Stage (MIS) 13/14 boundary to MIS 9 (535 to 300 ka). During the Mid-Brunhes event, the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate (NAR) values and by the blooming of the opportunistic genus Gephyrocapsa. Changes in coccolithophore abundance are also related to glacial-interglacial cycles. Higher NAR and numbers of coccoliths/g mainly occurred during the interglacial periods, while these values decreased during the glacial... |
| Tipo: Text |
Palavras-chave: North Atlantic Ocean; Mid-Pleistocene; Coccolithophores; Paleoclimate; Paleoproductivity. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00092/20286/17946.pdf |
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| Rogerson, M.; Colmenero-hidalgo, E.; Levine, R. C.; Rohling, E. J.; Voelker, A. H. L.; Bigg, G. R.; Schoenfeld, J.; Cacho, I.; Sierro, F. J.; Lowemark, L.; Reguera, M. I.; De Abreu, L.; Garrick, K.. |
| The Atlantic-Mediterranean exchange of water at Gibraltar represents a significant heat and freshwater sink for the North Atlantic and is a major control on the heat, salt and freshwater budgets of the Mediterranean Sea. Consequently, an understanding of the response of the exchange system to external changes is vital to a full comprehension of the hydrographic responses in both ocean basins. Here, we use a synthesis of empirical (oxygen isotope, planktonic foraminiferal assemblage) and modeling (analytical and general circulation) approaches to investigate the response of the Gibraltar Exchange system to Atlantic freshening during Heinrich Stadials (HSs). HSs display relatively flat W-E surface hydrographic gradients more comparable to the Late Holocene... |
| Tipo: Text |
Palavras-chave: Atlantic; Mediterranean; Gibraltar; Heinrich Event; Last Glacial Maximum; Mediterranean Outflow. |
| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00231/34189/32775.pdf |
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| 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 |
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| Rodrigues, T.; Voelker, A. H. L.; Grimalt, J. O.; Abrantes, F.; Naughton, F.. |
| Past sea surface water conditions of the western Iberian Margin were reconstructed based on biomarker analyses of a marine deep sea core MD03-2699 from the Estremadura Spur north off Lisbon, providing new insights into orbital and suborbital-scale climate variability between marine isotope stage (MIS) 15 to MIS 9 (580 to 300 ka). We use biomarker-based proxy records such as the alkenone unsaturated index to estimate sea surface temperature (SST), the total alkenone concentration to reconstruct phytoplankton productivity, and terrestrial biomarkers to evaluate the continental input. The results extend the existing biomarker record, namely the SST for the Iberian Margin, back to the sixth climatic cycle (580 ka). A general trend of stable interglacials... |
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| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00228/33879/32246.pdf |
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| Voelker, A. H. L.; Rodrigues, T.; Billups, K.; Oppo, D.; Mcmanus, J.; Stein, R.; Hefter, J.; Grimalt, J. O.. |
| Stable isotope and ice-rafted debris records from three core sites in the mid-latitude North Atlantic (IODP Site U1313, MD01-2446, MD03-2699) are combined with records of ODP Sites 1056/1058 and 980 to reconstruct hydrographic conditions during the middle Pleistocene spanning Marine Isotope Stages (MIS) 9-14 (300-540 ka). Core MD03-2699 is the first high-resolution mid-Brunhes record from the North Atlantic's eastern boundary upwelling system covering the complete MIS 11c interval and MIS 13. The array of sites reflect western and eastern basin boundary current as well as north to south transect sampling of subpolar and transitional water masses and allow the reconstruction of transport pathways in the upper limb of the North Atlantic's circulation.... |
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| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00231/34256/32633.pdf |
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