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| Registros recuperados: 10 | |
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| Galaasen, Eirik Vinje; Ninnemann, Ulysses S.; Kessler, Augustin; Irvalı, Nil; Rosenthal, Yair; Tjiputra, Jerry; Bouttes, Nathaëlle; Roche, Didier M.; Kleiven, Helga (kikki) F.; Hodell, David A.. |
| Disrupting North Atlantic Deep Water (NADW) ventilation is a key concern in climate projections. We use (sub)centennially resolved bottom water δ13C records that span the interglacials of the last 0.5 million years to assess the frequency of and the climatic backgrounds capable of triggering large NADW reductions. Episodes of reduced NADW in the deep Atlantic, similar in magnitude to glacial events, have been relatively common and occasionally long-lasting features of interglacials. NADW reductions were triggered across the range of recent interglacial climate backgrounds, which demonstrates that catastrophic freshwater outburst floods were not a prerequisite for large perturbations. Our results argue that large NADW disruptions are more easily achieved... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00663/77524/79329.pdf |
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| Obrochta, Stephen P.; Crowley, Thomas J.; Channell, James E. T.; Hodell, David A.; Baker, Paul A.; Seki, Arisa; Yokoyama, Yusuke. |
| A composite North Atlantic record from DSDP Site 609 and IODP Site U1308 spans the past 300,000 years and shows that variability within the penultimate glaciation differed substantially from that of the surrounding two glaciations. Hematite-stained grains exhibit similar repetitive down-core variations within the Marine Isotope Stage (MIS) 8 and 4-2 intervals, but little cyclic variability within the MIS 6 section. There is also no petrologic evidence, in terms of detrital carbonate-rich (Heinrich) layers, for surging of the Laurentide Ice Sheet through the Hudson Strait during MIS 6. Rather, very high background concentration of iceberg-rafted debris (IRD) indicates near continuous glacial meltwater input that likely increased thermohaline disruption... |
| Tipo: Text |
Palavras-chave: Insolation; IRD; Heinrich Event; MIS 6; MIS 8; AMOC. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00289/40050/38793.pdf |
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| Dixit, Yama; Hodell, David A.; Giesche, Alena; Tandon, Sampat K.; Gazquez, Fernando; Saini, Hari S.; Skinner, Luke C.; Mujtaba, Syed A. I.; Pawar, Vikas; Singh, Ravindra N.; Petrie, Cameron A.. |
| Today the desert margins of northwest India are dry and unable to support large populations, but were densely occupied by the populations of the Indus Civilization during the middle to late Holocene. The hydroclimatic conditions under which Indus urbanization took place, which was marked by a period of expanded settlement into the Thar Desert margins, remains poorly understood. We measured the isotopic values (delta O-18 and delta D) of gypsum hydration water in paleolake Karsandi sediments in northern Rajasthan to infer past changes in lake hydrology, which is sensitive to changing amounts of precipitation and evaporation. Our record reveals that relatively wet conditions prevailed at the northern edge of Rajasthan from similar to 5.1 +/- 0.2 ka BP,... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00434/54589/55970.pdf |
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| Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C.; Peck, Victoria L.; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Riveiros, Natalia Vazquez; Hodell, David A.. |
| Explanations of the glacial-interglacial variations in atmospheric pCO(2) invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected delta O-18... |
| Tipo: Text |
Palavras-chave: South Atlantic; Density gradient; Ocean stratification; Last deglaciation; Atmospheric CO2. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53276/54569.pdf |
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| Margari, Vasiliki; Skinner, Luke C.; Hodell, David A.; Martrat, Belen; Toucanne, Samuel; Grimalt, Joan O.; Gibbard, Philip L.; Lunkka, J. P.; Tzedakis, P. C.. |
| Past glacials can be thought of as natural experiments in which variations in boundary conditions influenced the character of climate change. However, beyond the last glacial, an integrated view of orbital-and millennial-scale changes and their relation to the record of glaciation has been lacking. Here, we present a detailed record of variations in the land-ocean system from the Portuguese margin during the penultimate glacial and place it within the framework of ice-volume changes, with particular reference to European ice-sheet dynamics. The interaction of orbital-and millennial-scale variability divides the glacial into an early part with warmer and wetter overall conditions and prominent climate oscillations, a transitional mid-part, and a late part... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00187/29819/28295.pdf |
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| Xuan, Chuang; Channel, James E. T.; Hodell, David A.. |
| The sediment sequence from Integrated Ocean Drilling Program (IODP) Site U1304 (53 degrees 03.40'N, 33 degrees 31.78'W; water depth, 3024 m) on the southern Gardar Drift, North Atlantic Ocean, covers the last similar to 1.8 Myr with a mean sedimentation rate of similar to 15 cm/kyr. At Site U1304, paleomagnetic directional and relative paleointensity (RPI) records have been generated for the last similar to 1.5 Myr, and benthic oxygen isotope data for the last similar to 1 Myr. The age model for Site U1304 was established by matching 6180 and RPI data to calibrated reference records. Prominent intervals of diatom mats at Site U1304 are associated with the latter stages of interglacial marine isotope stages (MIS) 9, 11, 13, 15, 21, 27 and 35, and with the... |
| Tipo: Text |
Palavras-chave: Quaternary; North Atlantic; Relative paleointensity; Magnetic excursions; Oxygen isotopes; Diatoms; IODP Site U1304. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53238/83373.pdf |
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| Margari, Vasiliki; Skinner, Luke C.; Menviel, Laurie; Capron, Emilie; Rhodes, Rachael H.; Mleneck-vautravers, Maryline J.; Ezat, Mohamed M.; Martrat, Belen; Grimalt, Joan O.; Hodell, David A.; Tzedakis, Polychronis C.. |
| The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. Here, we present joint marine and terrestrial analyses from the Portuguese Margin, showing a succession of cold stadials and warm interstadials over the interval 35–57 ka. Heinrich stadials 4 and 5 contain considerable structure, with a short transitional phase leading to an interval of maximum cooling and aridity, followed by slowly increasing sea-surface temperatures and moisture availability. A climate model experiment reproduces the changes in western Iberia during the final part of Heinrich stadial 4 as a result of the gradual recovery of the Atlantic meridional overturning circulation. What emerges is... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75476/76313.pdf |
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| Sierro, Francisco J.; Andersen, Nils; Bassetti, Maria-angela; Berne, Serge; Canals, Miquel; Curtis, Jason H.; Dennielou, Bernard; Abel Flores, Jose; Frigola, Jaime; Gonzalez-mora, Beatriz; Grimalt, Joan O.; Hodell, David A.; Jouet, Gwenael; Perez-folgado, Marta; Schneider, Ralph. |
| Direct traces of past sea levels are based on the elevation of old coral reefs at times of sea level high-stands. However, these measurements are discontinuous and cannot be easily correlated with climate records from ice cores. In this study we show a new approach to recognizing the imprint of sea level changes in continuous sediment records taken from the continental slope at locations that were continuously submerged, even during periods of sea level lowstand. By using a sediment core precisely synchronized with Greenland ice cores, we were able to recognize major floods of the Mediterranean continental shelf over the past 270 kyr. During the last glacial period five flooding events were observed at the onset of the warmest Greenland interstadials.... |
| Tipo: Text |
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| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/2009/publication-6969.pdf |
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| Petrie, Cameron A.; Singh, Ravindra N.; Bates, Jennifer; Dixit, Yama; French, Charly A. I.; Hodell, David A.; Jones, Penelope J.; Lancelotti, Carla; Lynam, Frank; Neogi, Sayantani; Pandey, Arun K.; Parikh, Danika; Pawar, Vikas; Redhouse, David I.; Singh, Dheerendra P.. |
| This paper explores the nature and dynamics of adaptation and resilience in the face of a diverse and varied environmental and ecological context using the case study of South Asia’s Indus Civilization (ca. 3000–1300 BC). Most early complex societies developed in regions where the climatic parameters faced by ancient subsistence farmers were varied but rain falls primarily in one season. In contrast, the Indus Civilization developed in a specific environmental context that spanned a very distinct environmental threshold, where winter and summer rainfall systems overlap. There is now evidence to show that this region was directly subject to climate change during the period when the Indus Civilization was at its height (ca. 2500–1900 BC). The Indus... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00369/47977/48002.pdf |
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| Registros recuperados: 10 | |
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