Consulta: subjectFacets:"Paleoceanography"
Registros recuperados: 49
Data/hora: 06/06/2024 16:35:11

Mg/Ca ratios in the planktonic foraminifer Neogloboquadrina pachyderma (sinistral) in the northern North Atlantic/Nordic Seas
Provedor de dados: 5
Autores: Meland, My; Jansen, E; Elderfield, H; Dokken, Tm; Olsen, A; Bellerby, Rgj.
In core top samples in the Nordic Seas, Mg/Ca ratios of N. pachyderma ( sin.) are generally consistent with previous high-latitude calibration data but do not reflect the modern calcification temperature gradient from 2 degrees C in the northwest to 8 degrees C in the southeast. This is because Mg/Ca ratios in foraminiferal shells from the central Nordic Seas are similar to 0.4 mmol/mol higher than expected from calibrations of Nurnberg ( 1995) and Elderfield and Ganssen ( 2000). The enhanced Mg/Ca ratios are observed in an area with low sedimentation rates (&lt; similar to 5 cm/kyr). Possible factors that may cause this include bioturbation, Holocene variability in old core tops, dissolution, pore water chemistry, occurrence of volcanic ash, and other...
Tipo: Text
Palavras-chave: Planktonic foraminifera; N. pachyderma (sin.); Mg/Ca; Paleothermometry; Paleoceanography; Nordic Seas.
Ano: 2006
URL: https://archimer.ifremer.fr/doc/00234/34559/33319.pdf

Impact of deglacial and Holocene AMOC changes on the mixed layer and deepwater hydrography of the subtropical North Atlantic
Provedor de dados: 5
Autores: Respschläger, Janne.
The Atlantic meridional overturning circulation (AMOC) transports warm saline water from low to high northern latitudes where it cools, sinks down and returns southward as deepwater flow. By the heat transfer from low to high latitudes, AMOC contributes in balancing the global energy budget and thus is an important part of global climate system. Within this study the impact of AMOC changes on surface and deepwater hydrography of the subtropical North Atlantic is investigated by the use of high-resolution sediment cores from a coring site located south of the Azores at the eastern flank of the Mid Atlantic Ridge. The Azores coring site is situated in the subtropical eastern North Atlantic (NA) at the boundary between warm Subtropical Gyre Water (STG) and...
Tipo: Text
Palavras-chave: Paleoceanography; AMOC; Subtropical gyre; Deglacial; Multiproxy SST; BWT; Stable isotopes; Planktonic and benthic foraminifera.
Ano: 2013
URL: https://archimer.ifremer.fr/doc/00493/60444/63889.pdf

Deep sea sedimentary analogs for the Vostok ice core
Provedor de dados: 5
Autores: Mortyn, Pg; Charles, Cd; Ninnemann, Us; Ludwig, K; Hodell, Da.
Many applications of the Vostok ice core depend critically on the ability to make stratigraphic ties to marine records in the adjacent Southern Ocean. Here we present oxygen isotopic records from high accumulation rate sites in the South Atlantic sector of the Southern Ocean, collected for the purpose of complementing the recently extended deltaD record from the Vostok ice core. The combination of several planktonic foraminiferal delta(18)O records from northern subantarctic piston cores demonstrates that all of the millennial-scale oscillations expressed in the Vostok ice core over the last 60 ky are also present in marine records. The observations also support the assumption that the millennial-scale oscillations common to both marine and ice archives...
Tipo: Text
Palavras-chave: Paleoclimatology; Paleoceanography; Meteorology and atmospheric dynamics : paleoclimatology.
Ano: 2003
URL: https://archimer.ifremer.fr/doc/00226/33707/32126.pdf

Climatic evolution of the central equatorial Pacific since the Last Glacial Maximum
Provedor de dados: 5
Autores: Seo, Inah; Lee, Yuri; Lee, Yong Il; Yoo, Chan Min; Hyeong, Kiseong.
This paper investigates paleoceanographic changes at a central equatorial Pacific site (6 degrees 40N, 177 degrees 28W) since the last glacial maximum using planktic foraminifera assemblages, together with the oxygen isotope (O-18) and Mg/Ca compositions of three species (Globigerinoides sacculifer, Pulleniatina obliquiloculata, and Globorotalia tumida) that dwell in the mixed layer, upper thermocline, and lower thermocline, respectively. While the Mg/Ca-derived temperatures of the mixed layer and lower thermocline varied within a narrow range from 18 ka onward, the upper thermocline temperature increased by as much as 3 degrees C during the last deglaciation (18-12 ka) with a simultaneous decrease of O-18. These changes are best explained by an enhanced...
Tipo: Text
Palavras-chave: Planktic foraminifera; Geochemistry; Micropaleontology; Paleoceanography; Intertropical Convergence Zone; Last deglaciation.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00496/60721/65271.pdf

Nd isotope constraints on ocean circulation, paleoclimate, and continental drainage during the Jurassic breakup of Pangea
Provedor de dados: 5
Autores: Dera, Guillaume; Prunier, Jonathan; Smith, Paul L.; Haggart, James W.; Popov, Evgeny; Guzhov, Alexander; Rogov, Mikhail; Delsate, Dominique; Thies, Detlev; Cuny, Gilles; Puceat, Emmanuelle; Charbonnier, Guillaume; Bayon, Germain.
The breakup of Pangea and onset of growth of the Pacific plate led to several paleoenvironmental feedbacks, which radically affected paleoclimate and ocean chemistry during the Jurassic. Overall, this period was characterized by intense volcanic degassing from large igneous provinces and circum-Panthalassan arcs, new oceanic circulation patterns, and changes in heat and humidity transports affecting continental weathering. Few studies, however, have attempted to unravel the global interactions linking these processes over the long-term. In this paper, we address this question by documenting the global changes in continental drainage and surface oceanic circulation for the whole Jurassic period. For this purpose, we present 53 new neodymium isotope values...
Tipo: Text
Palavras-chave: Neodymium isotopes; Jurassic; Paleoclimate; Paleoceanography; Continental drainage.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00179/29015/27443.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

Cyclic evolution of phytoplankton forced by changes in tropical seasonality
Provedor de dados: 5
Autores: Beaufort, Luc; Bolton, Clara T; Sarr, Anta-clarisse; Sucheras-marx, Baptiste; Rosenthal, Yair; Donnadieu, Yannick; Barbarin, Nicholas; Bova, Samantha; Cornuault, Pauline; Gally, Yves; Gray, Emmeline; Mazur, Jean-charles; Tetard, Martin.
The effect of global climate cycles driven by Earth’s orbital variations on evolution is poorly understood because of difficulties achieving sufficiently-resolved records of past evolution. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable an exceptional assessment of the impact of cyclic orbital-scale climate change on evolution because of their abundance in marine sediments, and because coccolithophores demonstrate extreme morphological plasticity in response to the changing environment1,2. Recently, evolutionary genetic analyses linked broad changes in Pleistocene fossil coccolith morphology to species radiation events3. Here, using high-resolution coccolith data, we show that during the last 2.8 million years...
Tipo: Text
Palavras-chave: Paleoceanography; Climate cycles; Global carbon cycle; Phytoplankton evolution; Tropical seasonality.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00658/77054/78353.pdf

The Mesolithic-Neolithic transition in southern Iberia
Provedor de dados: 5
Autores: Cortes Sanchez, Miguel; Jimenez Espejo, Francisco J.; Simon Vallejo, Maria D.; Gibaja Bao, Juan F.; Carvalho, Antonio Faustino; Martinez-ruiz, Francisca; Rodrigo Gamiz, Marta; Flores, Jose-abel; Paytan, Adina; Lopez Saez, Jose A.; Pena-chocarro, Leonor; Carrion, Jose S.; Morales Muniz, Arturo; Rosello Izquierdo, Eufrasia; Riquelme Cantal, Jose A.; Dean, Rebecca M.; Salgueiro, Emilia; Martinez Sanchez, Rafael M.; De La Rubia De Gracia, Juan J.; Lozano Francisco, Maria C.; Vera Pelaez, Jose L.; Llorente Rodriguez, Laura; Bicho, Nuno F.
New data and a review of historiographic information from Neolithic sites of the Malaga and Algarve coasts (southern Iberian Peninsula) and from the Maghreb (North Africa) reveal the existence of a Neolithic settlement at least from 7.5 cal ka BP. The agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the Mesolithic populations. The timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems, including upwelling intensity, sea-level changes and increased aridity in the Sahara and along the Iberian coast. These changes likely impacted the subsistence strategies of the Mesolithic populations along the Iberian seascapes and resulted in...
Tipo: Text
Palavras-chave: Abrupt climate change; Mesolithic-Neolithic transition; South Iberia; Holocene; Migration; Hunter-fisher-gatherers; Paleoceanography.
Ano: 2012
URL: https://archimer.ifremer.fr/doc/00266/37678/35767.pdf

Foraminiferal oxygen isotope stratigraphy and high-resolution organic carbon, carbonate records from the Okinawa Trough - (IMAGES MD012404 and ODP site 1202)
Provedor de dados: 5
Autores: Chang, Yp; Wu, Sm; Wei, Ky; Murayama, M; Kawahata, H; Chen, Mt.
Biogenic carbonate and organic carbon content of two deep sea cores (MD012404 and ODP site 1202) are measured to reconstruct surface ocean productivity variations in areas of the Okinawa Trough in the Western Pacific where the modern climate is highly sensitive to the East Asian monsoon and precipitation/river runoff. Based on foraminiferal isotope stratigraphy and AMS C-14 dating, the age models of the cores indicate that core MD012404 shows relatively low sedimentation rates with 50 cm ky(-1) on average, and that the sedimentation rates in core ODP 1202 are extremely high with an average of 500 cm ky(-1). Total organic carbon (TOC) and carbonate contents in core ODP 1202 are 0.56% and 6.80% on average, respectively, and are 0.62% and 15.86%,...
Tipo: Text
Palavras-chave: IMAGES; ODP; Total organic carbon; Calcium carbonate; Okinawa Trough; Paleoceanography; Climate change; East Asian monsoon.
Ano: 2005
URL: https://archimer.ifremer.fr/doc/00229/34064/32627.pdf

Variations of the ACC-CDW during MIS3 traced by magnetic grain deposition in midlatitude South Indian Ocean cores: Connections with the northern hemisphere and with central Antarctica
Provedor de dados: 5
Autores: Mazaud, A.; Kissel, C.; Laj, C.; Sicre, M. A.; Michel, E.; Turon, J. L.
We examine the magnetic mineral deposition in three cores located at midlatitude sites in the South Indian Ocean, in an area where sediment eroded from the Kerguelen-Crozet plateau and transported by the marine currents, principally the Antarctic Circum Current, accumulates at a high sedimentation rate. We focus on Marine Isotopic Stage 3, characterized by large climatic fluctuations at northern latitudes, and compare the obtained records to the climatic records at Byrd ( Antarctica) and Summit (GISP2, Greenland) and to the North Atlantic Deep Water variations in the North Atlantic. Magnetic mineral deposition at the studied sites exhibits a profile with maxima at the time of Heinrich events H4 and H5, which suggests a strong Antarctic Circum Current when...
Tipo: Text
Palavras-chave: Paleoceanography; South; Indian; Ocean; Paleoclimatology and paleoceanography; Environmental magnetism; Interhemispheric phasing.
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00235/34612/32954.pdf

Alkenone distributions in the North Atlantic and Nordic sea surface waters
Provedor de dados: 5
Autores: Sicre, Ma; Bard, E; Ezat, U; Rostek, F.
The C(37)-C(39) alkenones were quantified in suspended particulate matter obtained from the surface waters of the North Atlantic, including the Nordic seas, over a temperature range of 4degrees20 C. U(37)(K') values were linearly correlated to temperature over the entire range covered by our data set, i.e., 420 C (U(37)(K') = 0.027T + 0.036, r(2) = 0.97). The compilation of water column data from the Atlantic, Pacific, and Southern Ocean and Mediterranean Sea suggests that the linear model may not be the best function for fitting U(37)(K') and in situ temperature values. It also shows that suspended matter data from warm waters (T &gt;20degreesC) are still needed to constrain the equation of the global curve. High abundances of C(37: 4) were found in the...
Tipo: Text
Palavras-chave: Alkenones; Paleotemperature; Calibration; Atlantic Ocean; Plankton; Geochemistry; Marine geochemistry; Global change; Biogeochemical processes (4805); Oceanography; Paleoceanography.
Ano: 2002
URL: https://archimer.ifremer.fr/doc/00223/33393/31866.pdf

The last occurrence of Proboscia curvirostris in the North Atlantic marine isotope stages 9-8
Provedor de dados: 5
Autores: Koc, N; Labeyrie, L; Manthe, S; Flower, Bp; Hodell, Da; Aksu, A.
Well-preserved diatoms are present in high sedimentation rate Pleistocene cores retrieved on ocean Drilling Program (ODP) Legs 151, 152, 162 and IMAGES cruises of RN Marion Dufresne from the North Atlantic. Investigation of the stratigraphic occurrence of diatom species shows that the youngest diatom event observed in the area is the last occurrence (LO) of Proboscia curvirostris (Jouse) Jordan and Priddle. P. curvirostris is a robust species that can easily be identified in the sediments, and therefore can be a practical biostratigraphic tool. We have mapped its: areal distribution, and found that it stretches from 40 degreesN to 80 degreesN in the North Atlantic. Further, we have correlated the LO P. curvirostris to the oxygen isotope records of six...
Tipo: Text
Palavras-chave: Biostratigraphy; North Atlantic; Diatoms; Pleistocene; Paleoceanography; Isotope stratigraphy; Oxygen.
Ano: 2001
URL: https://archimer.ifremer.fr/doc/00221/33210/31708.pdf

Eastern Tropical Pacific Climate And El Niño Variability During The Past Millennium
Provedor de dados: 5
Autores: Rustic, Gerald Thomas.
The El Niño Southern Oscillation (ENSO) has been implicated in large-scale climate shifts of the past millennia, but paleoclimate records from the dynamically vital eastern equatorial Pacific Ocean (EEP) spanning the past millennium are sparse. This has limited our understanding of tropical Pacific dynamics, leaving questions regarding the source of ENSO variability unanswered. Here I seek to address some of these questions regarding relationship between ENSO and tropical Pacific mean state, and the relationship between the tropical Pacific and large-scale climate. Mean EEP sea surface temperature (SST) for the past millennium was reconstructed using Mg/Ca ratios in Globigerinoides ruber from a sub-centennially resolved sediment core collected near the...
Tipo: Text
Palavras-chave: Eastern tropical pacific; ENSO; Foraminifera; Paleoceanography; Paleoclimate.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00495/60657/64154.pdf

East Asian monsoon history and paleoceanography of the Japan Sea over the last 460,000 years
Provedor de dados: 5
Autores: Gallagher, Stephen J; Sagawa, Takuya; Henderson, Andrew C. G.; Saavedra-pellitero, Mariem; De Vleeschouwe, David; Black, Heather; Itaki, Takuya; Toucanne, Samuel; Bassetti, Maria-angela; Clemens, Steve; Anderson, William; Alvarez-zarikian, Carlos; Tada, Ryuji.
The Japan Sea is directly influenced by the Asian monsoon, a system that transports moisture and heat across southeast Asia during the boreal summer, and is a major driver of the Earth's ocean‐atmospheric circulation. Foraminiferal and facies analyses of a 460 kyr record from IODP Expedition 346 Site U1427 in the Japan Sea reveal a record of nutrient flux and oxygenation that varied due to sea level and East Asian monsoon intensity. The East Asian summer monsoon (EASM) was most intense during MIS (Marine Isotope Stage) 5e, 7e, 9e and 11c when the Tsushima Warm Current flowed into an unrestricted well mixed normal salinity Japan Sea. Whereas East Asian winter monsoon (EAWM) conditions dominated MIS 2, 4, 6 and 8 when sea level minima restricted the Japan...
Tipo: Text
Palavras-chave: Tsushima Warm Current; Pleistocene; Holocene; Paleoceanography; East Asian summer monsoon; East Asian winter monsoon.
Ano: 2018
URL: http://archimer.ifremer.fr/doc/00444/55591/57215.pdf

Late Quaternary changes in intermediate water oxygenation and oxygen minimum zone, northern Japan: A benthic foraminiferal perspective
Provedor de dados: 5
Autores: Shibahara, Akihiko; Ohkushi, Ken'Ichi; Kennett, James P.; Ikehara, Ken.
A strong oxygen minimum zone (OMZ) currently exists at upper intermediate water depths on the northern Japanese margin, NW Pacific. The OMZ results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters. We investigated late Quaternary history ( last 34 kyr) of ocean floor oxygenation and the OMZ using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off Shimokita Peninsula and Tokachi, northern Japan, at water depths between 975 and 1363 m. These cores are well located within the present-day OMZ, a region of high surface water productivity, and in close proximity to the source region of North Pacific Intermediate Water. Late...
Tipo: Text
Palavras-chave: Benthic foraminifera; Paleoceanography; Oyashio; Biological production; Last glacial; Deglacial; Holocene.
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00236/34733/33182.pdf

Orbital and suborbital climate variability in the Sulu Sea, western tropical Pacific
Provedor de dados: 5
Autores: Oppo, Dw; Linsley, Bk; Rosenthal, Y; Dannenmann, S; Beaufort, L.
A detailed record of planktic delta(18)O from a sediment core in the Sulu Sea, located between the South China Sea and the western Pacific warm pool, reveals that for the past 400 kyr (1 kyr = 1000 years), delta(18)O variability on orbital timescales is similar to that caused by changes in ice volume alone. This result indicates that in the Sulu Sea, temperature-driven changes in planktic delta(18)O on orbital times scales were generally compensated for by the effects of sea level and changes in seasonal monsoon intensity on the local freshwater budget, as well as by other changes in the tropical hydrologic cycle and their attendant effects on surface water delta(18)O. Increased freshening of the western tropical Pacific warm pool is reminiscent of La Nina...
Tipo: Text
Palavras-chave: Sulu Sea; Tropical hydrography; East Asian monsoon; IMAGES; Suborbital climate variability; Sea level; Paleoceanography; Marginal and semienclosed seas; Climate dynamics.
Ano: 2003
URL: https://archimer.ifremer.fr/doc/00226/33680/32047.pdf

Comparative geochemistry of four ferromanganese crusts from the Pacific Ocean and significance for the use of Ni isotopes as paleoceanographic tracers
Provedor de dados: 5
Autores: Gueguen, Bleuenn; Rouxel, Olivier; Rouget, Marie-laure; Bollinger, Claire; Ponzevera, Emmanuel; Germain, Yoan; Fouquet, Yves.
Ferromanganese (Fe-Mn) crusts are potential archive of the Ni isotope composition of seawater through time. In this study we aim at (1) understanding Ni isotope fractionation mechanisms and metal enrichment processes in Fe-Mn deposits, (2) addressing global vs. local control of Ni isotope composition of these deposits. Two Fe-Mn crusts from the North Pacific Ocean (Apuupuu Seamount, Hawaii) and two Fe-Mn crusts from the South Pacific Ocean (near Rurutu Island, Austral archipelago of French Polynesia) were characterized for their elemental geochemistry and Ni isotope composition. Geochemical analyses were performed at millimeter intervals in order to provide time-resolved record of Ni isotopes. Chronology and growth rates were determined using cosmogenic...
Tipo: Text
Palavras-chave: Ferromanganese crusts; Nickel isotopes; Paleoceanography; Pacific Ocean; Biogeochemical cycling.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00341/45255/44696.pdf

East Asian monsoon forcing of suborbital variability in the Sulu Sea during Marine Isotope Stage 3: Link to Northern Hemisphere climate
Provedor de dados: 5
Autores: Dannenmann, S; Linsley, Bk; Oppo, Dw; Rosenthal, Y; Beaufort, L.
We have generated a new high-resolution record of variations in planktonic foraminiferal oxygen isotopes (delta(18)O) and Mg/Ca from a sediment core (IMAGES 97-2141) in the Sulu Sea located in the Philippine archipelago of western tropical Pacific. This record reveals distinct, suborbital-scale delta(18)O changes, most notably during Marine Isotope Stage 3 (MIS3) (similar to30,000 to 60,000 years B.P.). The amplitudes of these delta(18)O fluctuations (0.4 to 0.7parts per thousand) exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions. In the same interval, variations in planktonic foraminifera Mg/Ca suggest that suborbital surface ocean temperature variations of 1 to 1.5degreesC in the Sulu Sea were...
Tipo: Text
Palavras-chave: Paleoceanography; Isotope stage 3; SE Asian Monsoon; Mg/Ca; Oxygen isotopes; Millennial-scale climate change; Paleoceanography; Climate dynamics.
Ano: 2003
URL: https://archimer.ifremer.fr/doc/00226/33681/32046.pdf

Glacial Ocean Dynamics: Insight from Deep-Sea Coral Reconstructions and A Time-Dependent Dynamical Box Model
Provedor de dados: 5
Autores: Hines, Sophia Katharine Vizza.
Glacial-interglacial cycles, occurring at a period of approximately 100,000 years, have dominated Earth's climate over the past 800,000 years. These cycles involve major changes in land ice, global sea level, ocean circulation, and the carbon cycle. While it is generally agreed that the ultimate driver of global climate is changes in insolation, glacial cycles do not look like insolation forcing. Notably, there is a highly non-linear warming response at 100,000 years to a relatively small forcing, implicating a more complicated system of biogeochemical and physical drivers. The ocean plays a pivotal role in glacial-interglacial climate through direct equator-to-pole transport of heat and its role in the carbon cycle. The deep ocean contains 60 times more...
Tipo: Text
Palavras-chave: Paleoceanography; Oceanography; Climate change; Glacial cycles; Ocean circulation; Ocean dynamics.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00493/60447/63892.pdf

Reconciling down core anticorrelation of diatom carbon and nitrogen isotopic ratios from the Southern Ocean
Provedor de dados: 5
Autores: Crosta, X; Shemesh, A.
[1] Oceanic nutrient cycling in the Southern Ocean is supposed to have an important impact on glacial-interglacial atmospheric CO(2) changes and global climate. In order to characterize such nutrient cycling over the last two climatic cycles we investigated carbon and nitrogen isotopic ratios of diatom-bound organic matter (delta(13)C(diat) and delta(15)N(diat)- respectively) in two cores retrieved form the Atlantic and Indian sectors of the Antarctic Ocean. The two cores show the same isotopic patterns. The delta(13)C(diat) values are depleted during glacial periods and enriched during interglacial periods, indicating lower productivity during cold times. The delta(15)N(diat) values are enriched during glacial periods and depleted during interglacial...
Tipo: Text
Palavras-chave: Southern Ocean; Paleoceanography; Geochemistry; Diatoms.
Ano: 2002
URL: https://archimer.ifremer.fr/doc/00223/33402/31859.pdf

Biogenic sedimentation patterns in the northern South China Sea: An ultrahigh-resolution record MD972148 of the past 150,000 years from the IMAGES III-IPHIS cruise
Provedor de dados: 5
Autores: Chen, Yy; Chen, Mt; Fang, Ts.
Ultrahigh resolution records of carbonate and organic carbon concentrations from core MD972148 (19 degrees 47.804'N 117 degrees 32.56'E; water depth 2830 m) provide information on glacial-interglacial as well as millennial to centennial scale variability in the production of biogenic sediments in the northern slope of the South China Sea (SCS) over the past 150,000 years. A preliminary age model of this record is estimated using a biostratigraphic datum of Globigerinoides ruber (pink) and the relationship of carbonate concentrations and partial derivative(18)O of planktonic foraminifers shown in previous SCS records. The downcore patterns in this record show that the carbonate concentration maxima correspond to interglacial times and minima correspond to...
Tipo: Text
Palavras-chave: Paleoceanography; Late Quaternary; Carbonate sedimentology; South China Sea.
Ano: 1999
URL: https://archimer.ifremer.fr/doc/00239/35072/34559.pdf

Rare earth elements and neodymium isotopes in sedimentary organic matter
Provedor de dados: 5
Autores: Freslon, Nicolas; Bayon, Germain; Toucanne, Samuel; Bermell, Sylvain; Bollinger, Claire; Chéron, Sandrine; Etoubleau, Joel; Germain, Yoan; Khripounoff, Alexis; Ponzevera, Emmanuel; Rouget, Marie Laure.
We report rare earth element (REE) and neodymium (Nd) isotope data for the organic fraction of sediments collected from various depositional environments, i.e. rivers (n=25), estuaries (n=18), open-ocean settings (n=15), and cold seeps (n=12). Sedimentary Organic Matter (SOM) was extracted using a mixed hydrogen peroxide/nitric acid solution (20%-H2O2 – 0.02M-HNO3), after removal of carbonate and oxy-hydroxide phases with dilute hydrochloric acid (0.25M-HCl). A series of experimental tests indicate that extraction of sedimentary organic compounds using H202 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates. However, this contamination is expected to be minor for REE because measured concentrations in H2O2...
Tipo: Text
Palavras-chave: Organic matter; Rare earth elements; REE; Neodymium isotopes; ΕNd; Sediment; Boundary Exchange; Paleoceanography.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00191/30250/28682.pdf

Carbon and silica megasink in deep-sea sediments of the Congo terminal lobes
Provedor de dados: 5
Autores: Rabouille, C.; Dennielou, Bernard; Baudin, F.; Raimonet, M.; Droz, Laurence; Khripounoff, Alexis; Martinez, P.; Mejanelle, L.; Michalopoulos, P.; Pastor, Lucie; Pruski, A.; Ragueneau, Olivier; Reyss, J.-l.; Ruffine, Livio; Schnyder, J.; Stetten, E.; Taillefert, M.; Tourolle, Julie; Olu, Karine.
Carbon and silicon cycles at the Earth surface are linked to long-term variations of atmospheric CO2 and oceanic primary production. In these cycles, the river-sea interface is considered a biogeochemical hotspot, and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments. In contrast, periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep-sea via submarine canyons and accumulation in deep-sea fans. Here, we calculate present-day mass balances for organic carbon (OC) and amorphous silica (aSi) in the terminal lobe complex of the Congo River deep-sea fan as an analogue for glacial periods. We show that this lobe complex constitutes a megasink with the current...
Tipo: Text
Palavras-chave: Present; Paleoceanography; South Atlantic; Inorganic geochemistry; Organic geochemistry; Sedimentology-marine cores.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00511/62289/66720.pdf

Climate and ocean forcing of ice-sheet dynamics along the Svalbard-Barents Sea Ice Sheet during the deglaciation ∼20,000–10,000 years BP
Provedor de dados: 5
Autores: Rasmussen, Tine L.; Thomsen, Erik.
The last deglaciation, 20,000–10,000 years ago, was a period of global warming and rapidly shrinking ice sheets. It was also climatically unstable and retreats were interrupted by re-advances. Retreat rates and timing relative to climatic changes have therefore been difficult to establish. We here study a suite of 12 marine sediment cores from Storfjorden and Storfjorden Trough, Svalbard. The purpose is to reconstruct retreat patterns and retreat rates of a high northern latitude marine-based ice stream from the Svalbard-Barents Sea Ice Sheet in relation to paleoceanographic and paleoclimatic changes. The study is based on abundance and composition of planktic and benthic foraminiferal assemblages, ice rafted debris (IRD), lithology, and 70 AMS-14C dates....
Tipo: Text
Palavras-chave: Ice retreat rates; Storfjorden ice stream; Paleoceanography; Paleoclimate; Paleotemperature.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00658/77019/78289.pdf

Palynological investigation of Holocene climatic and oceanic variability in South Africa and the southern Benguela upwelling system
Provedor de dados: 5
Autores: Zhao, Xueqin.
South Africa is very sensitive to climate change, because it is located between two atmospheric systems (subtropical and warm-temperate systems) and two oceanic systems (Benguela Current and Agulhas Current). Presently, the seasonal changes of atmospheric and oceanic systems induce a pronounced rainfall seasonality comprised of three different rainfall zones (summer rainfall zone, SRZ; year-round rainfall zone, YRZ and winter rainfall zone, WRZ) over South Africa. However, the seasonality development during the Holocene in South Africa is poorly understood and the driving forces of the climate change are debated. Therefore, this study aims to provide a detailed reconstruction of Holocene climate and vegetation variability of South Africa,...
Tipo: Text
Palavras-chave: Holocene; Marine sediments; Pollen; Microcharcoal; Organic-walled dinoflagellate cyst; Paleoenvironment; Paleoceanography; South Africa.
Ano: 2017
URL: https://archimer.ifremer.fr/doc/00493/60442/63887.pdf

Ice-shelf collapse from subsurface warming as a trigger for Heinrich events
Provedor de dados: 5
Autores: Marcott, Shaun A.; Clark, Peter U.; Padman, Laurie; Klinkhammer, Gary P.; Springer, Scott R.; Liu, Zhengyu; Otto-bliesner, Bette L.; Carlson, Anders E.; Ungerer, Andy; Padman, June; He, Feng; Cheng, Jun; Schmittner, Andreas.
Episodic iceberg-discharge events from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich events, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface warming at the same time as large reductions in the AMOC, with temperature increasing by approximately 2 C over a 1-2 kyr interval prior to a Heinrich event. In simulations with an ocean model coupled to a thermodynamically...
Tipo: Text
Palavras-chave: Paleoceanography; Paleoclimatology; Abrupt climate change.
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00227/33819/32479.pdf

Deep sea records from the southeast Labrador Sea: Ocean circulation changes and ice-rafting events during the last 160,000 years
Provedor de dados: 5
Autores: Rasmussen, Tl; Oppo, Dw; Thomsen, E; Lehman, Sj.
[1] Results from two deep sea cores from northeast of Newfoundland at 1251 and 2527 m water depth, respectively, indicate that during the time period from 160,000 to 10,000 years BP, ice rafting events in the Labrador Sea were accompanied by rapid variations in deep and surface water circulation. Twelve ice-rafting events occurred, each coinciding with high concentrations of detrital carbonate and oxygen isotopic depletion of both surface and bottom waters. Eleven of these can be correlated with the North Atlantic Heinrich events H1-H11. The remaining very conspicuous ice-rafting event took place early in MIS substage 5e, at a time when the planktic faunal assemblage suggests marked warming of the sea surface. In the shallower core, benthic delta(13)C...
Tipo: Text
Palavras-chave: Paleoceanography; Labrador Sea; Ice rafting; Foraminifera; Last climate cycle.
Ano: 2003
URL: https://archimer.ifremer.fr/doc/00496/60768/65083.pdf

Independent tephrochronological evidence for rapid and synchronous oceanic and atmospheric temperature rises over the Greenland stadial-interstadial transitions between ca. 32 and 40 ka b2k
Provedor de dados: 5
Autores: Berben, Sarah M.p.; Dokken, Trond M.; Abbott, Peter M.; Cook, Eliza; Sadatzki, Henrik; Simon, Margit H; Jansen, Eystein.
Understanding the dynamics that drove past abrupt climate changes, such as the Dansgaard-Oeschger (DO) events, depends on combined proxy evidence from disparate archives. To identify leads, lags and synchronicity between different climate system components, independent and robust chronologies are required. Cryptotephrochronology is a key geochronological tool as cryptotephra horizons can act as isochrons linking disparate and/or distant records. Here, we investigated marine sediment core MD99-2284 from the Norwegian Sea to look for previously identified Greenland ice core cryptotephra horizons and define time-parallel markers between the archives. We explored potential secondary transport and depositional mechanisms that could hamper the isochronous...
Tipo: Text
Palavras-chave: Quaternary; Paleoclimatology; Paleoceanography; North Atlantic; Sedimentology; Marine cores; Ice cores; Cryptotephrochronology; DO-Events; Synchronization.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00622/73391/72606.pdf

Neodymium isotopic composition and rare earth element concentrations in the deep and intermediate Nordic Seas: Constraints on the Iceland Scotland Overflow Water signature
Provedor de dados: 5
Autores: Lacan, F; Jeandel, C.
Neodymium isotopic composition and rare earth element concentrations were measured in seawater samples from eleven stations in the Nordic Seas. These data allow us to study how the Iceland Scotland Overflow Water ( ISOW) acquires its neodymium signature in the modern ocean. The waters overflowing the Faroe Shetland channel are characterized by epsilon(Nd) = -8.2 +/- 0.6, in good agreement with the only other data point, published 19 years ago. In the Greenland and Iceland Seas the water masses leading to the formation of the ISOW display lower neodymium isotopic composition, with epsilon(Nd) around -11 and -9, respectively. Since no water masses in the Nordic Seas are characterized by epsilon(Nd) &gt; -8, the radiogenic signature of the ISOW likely...
Tipo: Text
Palavras-chave: Iceland Scotland Overflow Water; Neodymium isotopic composition; Nordic Seas; North Atlantic; Rare earth; Sediment water mass interactions; Paleoceanography; Water masses; Geochemistry.
Ano: 2004
URL: https://archimer.ifremer.fr/doc/00228/33924/32308.pdf

Intermediate and deep ocean current circulation in the Mozambique Channel: New insights from ferromanganese crust Nd isotopes
Provedor de dados: 5
Autores: Charles, Claire; Pelleter, Ewan; Révillon, Sidonie; Nonnotte, Philippe; Jorry, Stephan; Kluska, Jean-michel.
The Mozambique Channel plays a key role in the exchange of water masses between the Indian and Atlantic Oceans, which include the North Atlantic Deep Water (NADW) inflow from the south and the North Indian Deep Water (NIDW), an aged form of the NADW spreading poleward from the northern and equatorial Indian Ocean basin. Several authors assume that the Davie Ridge acts as a topographic barrier to the northward advection of NADW, which would therefore be absent in the Comoros Basin. Other studies suggest that the NADW flows from the south of the Mozambique Channel to the Comoros Basin, indicating that the Davie Ridge may not currently constitute a blocking topographic barrier to deep water mass circulation. To address this question, we studied ferromanganese...
Tipo: Text
Palavras-chave: Ferromanganese crusts; Nd isotopes; Paleoceanography; Mozambique Channel; North Atlantic Deep Water.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00653/76488/77569.pdf

Monsoon variability and deep oceanic circulation in the western equatorial Pacific over the last climatic cycle: Insights from sedimentary magnetic properties and sortable silt
Provedor de dados: 5
Autores: Kissel, Catherine; Laj, Carlo; Kienast, Markus; Bolliet, Timothe; Holbourn, Ann; Hill, Paul; Kuhnt, Wolfgang; Braconnot, Pascale.
Magnetic and grain size properties of a sediment core located in the western equatorial Pacific, off the southeastern tip of the Philippine island of Mindanao, are presented in an effort to reconstruct past changes in the East Asian Monsoon and deep ocean circulation during the last 160 kyrs. The sedimentary concentration of magnetic particles, interpreted to reflect past changes in runoff from Mindanao, varies almost in antiphase with Northern Hemisphere insolation. This suggests that precipitation was lower in the western equatorial Pacific region during boreal insolation maxima and thus corroborates model results showing opposing trends in precipitation between land and the marine realm there. Variations in the grain size distribution of the inorganic...
Tipo: Text
Palavras-chave: North atlantic; Grain size; Water; Core; Mindanao; Paleoceanography; Susceptibility; Anisotropy; Remanence; Iceland.
Ano: 2010
URL: https://archimer.ifremer.fr/doc/00207/31854/30262.pdf

Glacial reduction and millennial-scale variations in Drake Passage throughflow
Provedor de dados: 5
Autores: Lamy, Frank; Arz, Helge W.; Kilianc, Rolf; Lange, Carina B.; Lembke-jene, Lester; Wengler, Marc; Kaiser, Jerome; Baeza-urrea, Oscar; Hall, Ian R.; Harada, Naomi; Tiedemann, Ralf.
The Drake Passage (DP) is the major geographic constriction for the Antarctic Circumpolar Current (ACC) and exerts a strong control on the exchange of physical, chemical, and biological properties between the Atlantic, Pacific, and Indian Ocean basins. Resolving changes in the flow of circumpolar water masses through this gateway is, therefore, crucial for advancing our understanding of the Southern Ocean's role in global ocean and climate variability. Here, we reconstruct changes in DP throughflow dynamics over the past 65,000 y based on grain size and geochemical properties of sediment records from the southernmost continental margin of South America. Combined with published sediment records from the Scotia Sea, we argue for a considerable total...
Tipo: Text
Palavras-chave: Paleoceanography; Drake Passage; Antarctic Circumpolar Current; Glacial-interglacial changes; Sedimentology.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00351/46233/46119.pdf

High-resolution migration history of the Subtropical High/Trade Wind system of the northeastern Pacific during the last similar to 55 years: Implications for glacial atmospheric reorganization
Provedor de dados: 5
Autores: Cheshire, Heather; Thurow, Juergen.
Guaymas Basin, Gulf of California, is a restricted basin located under the present-day wet/dry subtropical divide (similar to 27 degrees N) and is ideally circumstanced for detecting variations in the North Pacific Subtropical High (NPSH)/Trade Wind system. Controlled by climate cell boundary displacement, NPSH midwinter location was the primary influence on timing and intensity of upwelling seasons in Guaymas Basin. Analysis of high-resolution X-ray fluoresence data and sediment fabric log from 75% laminated Core MD02-2517/2515, western Guaymas Basin, reveals systematic changes in NPSH behavior over the last similar to 55 kyr BP. Southward displacement of the wet/dry subtropical divide controlled upwelling-related diatom productivity, while sea level and...
Tipo: Text
Palavras-chave: Quaternary; Paleoceanography; X-ray fluorescence; Laminated sediment.
Ano: 2013
URL: https://archimer.ifremer.fr/doc/00264/37527/35762.pdf

Crystallinity of foraminifera shells: A proxy to reconstruct past bottom water CO(3)(=) changes?
Provedor de dados: 5
Autores: Bassinot, Fc; Melieres, F; Gehlen, M; Levi, C; Labeyrie, L.
The reconstruction of past changes in bottom water CO(3)(=) is central to evaluating competing oceanic scenarios that deal with long-term variations in atmospheric pCO(2). In search of a quantitative bottom water CO(3)(=) proxy, we analyzed the variations of calcite crystallinity of planktonic foraminifera Globigerinoides ruber shells picked from core top samples along three depth transects: Ontong Java Plateau and the northeast margin of Irian Jaya, in the western equatorial Pacific, and the Sierra Leone Rise, in the eastern tropical Atlantic. The strong empirical relationship between calcite crystallinity ( inferred from the full width at half maximum (FWHM) of calcite (104) X-ray diffraction peak) and bottom water saturation relative to calcite...
Tipo: Text
Palavras-chave: Bottom water CO(3); Calcite crystallinity; Carbonate dissolution; Foraminifers; Paleoceanography; Mineral physics : X ray; Neutron; Electron spectroscopy and diffraction.
Ano: 2004
URL: https://archimer.ifremer.fr/doc/00226/33716/32138.pdf

Constraints on surface seawater oxygen isotope change between the Last Glacial Maximum and the Late Holocene
Provedor de dados: 5
Autores: Waelbroeck, C.; Kiefer, T.; Dokken, T.; Chen, M. -t.; Spero, H. J.; Jung, S.; Weinelt, M.; Kucera, M.; Paul, A.
Estimates of the change in surface seawater delta O-18 (delta O-18(sw)) between the Last Glacial Maximum (LGM) and Late Holocene (LH) are derived from homogenous data sets with rigorous age control, namely MARGO sea surface temperature (SST) estimates and oxygen isotopic ratios (delta O-18) of planktonic foraminifers. Propagation of uncertainties associated with each proxy allows the identification of robust patterns of change in delta O-18(sw). Examination of these patterns on a regional scale highlights which changes in surface currents and hydrological cycle are consistent with both planktonic isotopic data and reconstructed SST. Positive local annual mean LGM-LH delta O-18(sw) anomalies characterize the glacial tropical Indian Ocean, portions of the...
Tipo: Text
Palavras-chave: Paleoceanography; Surface water oxygen isotopic ratio; Planktonic foraminifers; Last Glacial Maximum.
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00297/40870/39909.pdf

Atlas of modern dinoflagellate cyst distributions in the Black Sea Corridor: From Aegean to Aral Seas, including Marmara, Black, Azov and Caspian Seas
Provedor de dados: 5
Autores: Mudie, Peta J.; Marret, Fabienne; Mertens, Kenneth; Shumilovskikh, Lyudmila; Leroy, Suzanne A. G.
We present the first comprehensive taxonomic and environmental study of dinoflagellate cysts in 185 surface sediment samples from the Black Sea Corridor (BSC) which is a series of marine basins extending from the Aegean to the Aral Seas (including Marmara, Black, Azov and Caspian Seas). For decades, these low-salinity, semi-enclosed or endorheic basins have experienced large-scale changes because of intensive agriculture and industrialisation, with consequent eutrophication and increased algal blooms. The BSC atlas data provide a baseline for improved understanding of linkages between surface water conditions and dinoflagellate cyst (dinocyst) distribution, diversity and morphological variations. By cross-reference to dinocyst occurrences in sediment cores...
Tipo: Text
Palavras-chave: Phytoplankton; Harmful algae; Biodiversity; Paleoceanography; Surface samples.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00387/49824/50408.pdf

Cartographie du prisme sedimentaire Holocene en baie de Seine orientale, par sismique reflexion a haute definition
Provedor de dados: 5
Autores: Auffret, J; D'Ozouville, L.
After the cartography of a Holocene sedimentary prism, results of 8,000 years of natural evolution and 150 years of coastal equipment, the authors research an active sedimentary system, characteristic of present evolution.
Tipo: Text
Palavras-chave: Holocene; Sedimentary structures; Paleoceanography; Estuarine sedimentation; Sediment distribution; Seismic reflection profiling; Cartography.
Ano: 1985
URL: http://archimer.ifremer.fr/doc/1985/acte-1273.pdf

Tephra horizons identified in the western North Atlantic and Nordic Seas during the Last Glacial Period: Extending the marine tephra framework
Provedor de dados: 5
Autores: Rutledal, Sunniva; Berben, Sarah M.p.; Dokken, Trond M.; Van Der Bilt, Willem G.m.; Cederstrøm, Jan Magne; Jansen, Eystein.
Geochemically distinct volcanic ash (tephra) deposits are increasingly acknowledged as a key geochronological tool to synchronize independent paleoclimate archives. Recent advances in the detection of invisible (crypto) tephra have led to the ongoing establishment, development and integration of regional tephra lattices. These frameworks offer an overview of the spatial extent of geochemically characterized tephra from dated eruptions – a valuable tool for precise correlation of paleorecords within these areas. Here, we harness cryptotephra analysis to investigate the occurrence of two well-known tephra markers from the Last Glacial Period (i.e. FMAZ II-1 (26.7 ka b2k) and NAAZ II (II-RHY-1) (55.3 ka b2k)), in marine sediment cores from the Nordic,...
Tipo: Text
Palavras-chave: Tephrochronology; Cryptotephra Tephrostratigraphy; Tephra isochrons; FMAZ II; NAAZ II; Geochemistry; Paleoceanography; Marine sediment cores Quaternary; North Atlantic Ocean.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00614/72659/71665.pdf

Changes in the advection of Antarctic Intermediate Water to the northern Chilean coast during the last 970 kyr
Provedor de dados: 5
Autores: Martinez-mendez, G.; Hebbeln, D.; Mohtadi, M.; Lamy, F.; De Pol-holz, R.; Reyes-macaya, D.; Freudenthal, Tim.
The Antarctic Intermediate Water (AAIW) is a key player in global-scale oceanic overturning processes and an important conduit for heat, fresh water, and carbon transport. The AAIW past variability is poorly understood mainly due to the lack of sedimentary archives at intermediate water depths. We present records of benthic stable isotopes from sediments retrieved with the seafloor drill rig MARUM-MeBo at 956m water depth off northern Chile (GeoB15016, 27 degrees 29.48S, 71 degrees 07.58W) that extend back to 970ka. The sediments at this site are presently deposited at the boundary between AAIW and Pacific Deep Water (PDW). For previous peak interglacials, our results reveal similar benthic C-13 values at site GeoB15016 and of a newly generated stack of...
Tipo: Text
Palavras-chave: Paleoceanography; AAIW; Advection changes.
Ano: 2013
URL: https://archimer.ifremer.fr/doc/00263/37459/35821.pdf

Ice-age variability from the Vostok deuterium and deuterium excess records
Provedor de dados: 5
Autores: Yiou, P; Vimeux, F; Jouzel, J.
The four climatic cycles obtained from the Vostok ice core offer a unique opportunity to study the high-frequency paleoclimatic variability, i.e., on time scales smaller than 15 kyr. We focused our study on the deuterium (deltaD) and deuterium excess (d) records, which are proxies for local temperature and remote evaporation source temperature and hence give us access to spatial climatic variations. Spectral analyses of paleoclimatic records have shown that the last glacial period (110-15 kyr before present) is characterized by large and fast temperature oscillations. Examples of such variations in the Northern Hemisphere are the so-called Dansgaard-Oeschger oscillations and Heinrich events. At Vostok, these oscillations are also imprinted in the ice, with...
Tipo: Text
Palavras-chave: Climate dynamics; Antarctica; Meteorology and Atmospheric Dynamics; Paleoclimatology; Paleoceanography.
Ano: 2001
URL: https://archimer.ifremer.fr/doc/00221/33219/31699.pdf

Timing of Svalbard/Barents Sea Ice Sheet Decay during the Last Glacial Termination
Provedor de dados: 5
Autores: Snow, Tasha.
The Arctic and North Atlantic underwent significant climactic changes since the Last Glacial Maximum (25,000 years before present (1950 AD); ka BP), but offsets in the timing of events between the two regions are poorly constrained due to age model uncertainties that arise from changing radiocarbon reservoir ages. Here, we use a relatively high-resolution, multi-proxy stable isotope and sedimentologic dataset from Eastern Fram Strait (ODP Leg 162 Site 986) marine sediments to constrain the timing of Svalbard/Barents Sea Ice Sheet decay and infer deglacial reservoir ages over the last 30 ka. We use magnetic susceptibility, inorganic and organic carbon, foraminiferal assemblage counts, planktonic foraminiferal isotopes, and iceberg-rafted debris proxies to...
Tipo: Text
Palavras-chave: Paleoceanography; Meltwater; Isotopes; Foraminifera; Fram Strait; Reservoir age.
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00499/61045/64452.pdf

Relationship of the tetra-unsaturated C-37 alkenone to salinity and temperature: Implications for paleoproxy applications
Provedor de dados: 5
Autores: Sikes, El; Sicre, Ma.
This study assesses the relationship to salinity and temperature of the levels of the tetra-unsaturated 37-carbon methyl alkenone (C-37:4) in the surface ocean. U-37(K'), a measure of the relative abundances of the C-37:2 and the C-37:3 alkenones, has a well constrained linear relationship to temperature in the open ocean [Prahl and Wakeham, 1987] and is a well-established technique for estimating past sea surface temperatures in the sediments (e. g. [Muller et al., 1998]). Unlike the di- and tri-unsaturated C-37 alkenones, the temperature response of the tetra-unsaturated C-37 alkenone is less certain [Sikes et al., 1997], and recent work has suggested a relationship to salinity instead [Rosell-Mele, 1998; Schulz et al., 2000]. Our study examined 106...
Tipo: Text
Palavras-chave: Alkenones; Paleosalinity; Marine organic geochemistry; Organic geochemistry; Paleoceanography; Organic marine chemistry.
Ano: 2002
URL: https://archimer.ifremer.fr/doc/00223/33414/31886.pdf

Late Holocene surface ocean conditions of the Norwegian Sea (Voring Plateau)
Provedor de dados: 5
Autores: Andersson, C; Risebrobakken, B; Jansen, E; Dahl, So.
Late Holocene sea surface ocean conditions of the eastern Norwegian Sea (Voring Plateau) are inferred from planktic stable isotopes and planktic foraminiferal assemblage changes in cores JM97-948/2A and MD95-2011 (66.97degreesN, 7.64degreesE). Strong covariance between the planktic stable oxygen isotopic record and abundance changes of N. pachyderma (sin) show that major changes in surface ocean conditions are reflected both in the geochemical composition of the foraminiferal tests as well as in the composition of the foraminiferal fauna. Surface ocean conditions warmer than present were common during the past 3000 years. During the so-called Medieval Warm Period, surface conditions were highly variable with marked changes in sea surface temperature. The...
Tipo: Text
Palavras-chave: Paleoceanography; Stable isotope; Holocene; Micropaleontology.
Ano: 2003
URL: https://archimer.ifremer.fr/doc/00224/33495/31954.pdf

Planktonic foraminiferal sea surface temperature variations in the southeast Atlantic Ocean: A high-resolution record MD962085 of the past 400,000 years from the IMAGES II-NAUSICAA cruise
Provedor de dados: 5
Autores: Chang, Yp; Chang, Cc; Wang, Lw; Chen, Mt; Wang, Ch; Yu, Ef.
A high-resolution (similar to 4 - 5cm/kyr) giant piston core record (MD962085) retrieved during an IMAGES II - NAUSICAA cruise from the continental slope of the southeast Atlantic Ocean reveal striking variations in planktonic foraminifer faunal abundances and sea-surface temperatures (SST) during the past 400,000 years. The location and high-quality sedimentary record of the core provide a good opportunity to assess changes in the intensity and position of the Benguela Current System and the Subtropical Convergence, two key features of the ocean-climate system in the south Atlantic. This record can be also used to evaluate the possible influence of Agulhas Current from the throughflow of the Indian Ocean into the South Atlantic. The planktonic foraminifer...
Tipo: Text
Palavras-chave: Paleoceanography; Late Quaternary; Micropaleontology; South Atlantic.
Ano: 1999
URL: https://archimer.ifremer.fr/doc/00239/35070/34563.pdf

Transform Marginal Plateaus
Provedor de dados: 5
Autores: Loncke, L.; Roest, Walter; Klingelhoefer, Frauke; Basile, C.; Graindorge, David; Heuret, A.; Marcaillou, B.; Museur, Thomas; Fanget, Anne-sophie; Mercier De Lépinay, M.
Numerous submarine plateaus form highstanding bathymetric highs at continent to ocean transitions. Due to their proximity to continents, they have been frequently labelled “marginal plateaus”, although this term has not been clearly defined or associated with a specific geology or geodynamic process. Until now, these elevations have been interpreted as submerged thinned continental fragments detached from continents, basaltic buildups formed by hotspots, volcanic margins or oceanic plateaus. Many of these plateaus formed at transform margins connecting oceanic basins of contrasted ages. We propose for the first time to define and review a class of marginal plateaus related to a specific tectonic setting: “Transform Marginal Plateaus” (TMPs). Based on a...
Tipo: Text
Palavras-chave: Transform marginal plateau; Transform margin; Volcanic margin; Large Igneous Province; Continental breakup; Paleoceanography; Land bridge; Gateway.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00512/62407/66663.pdf

A dynamic explanation for the origin of the western Mediterranean organic-rich layers
Provedor de dados: 5
Autores: Rogerson, M.; Cacho, I.; Jimenez-espejo, F.; Reguera, M. I.; Sierro, F. J.; Martinez-ruiz, F.; Frigola, J.; Canals, M.
The eastern Mediterranean sapropels are among the most intensively investigated phenomena in the paleoceanographic record, but relatively little has been written regarding the origin of the equivalent of the sapropels in the western Mediterranean, the organic-rich layers (ORLs). ORLs are recognized as sediment layers containing enhanced total organic carbon that extend throughout the deep basins of the western Mediterranean and are associated with enhanced total barium concentration and a reduced diversity (dysoxic but not anoxic) benthic foraminiferal assemblage. Consequently, it has been suggested that ORLs represent periods of enhanced productivity coupled with reduced deep ventilation, presumably related to increased continental runoff, in close...
Tipo: Text
Palavras-chave: Sapropel; Mediterranean; Sea level; Paleoceanography; Circulation.
Ano: 2008
URL: https://archimer.ifremer.fr/doc/00237/34825/33303.pdf

Recording of ocean-climate changes during the last 2,000 years in a hypoxic marine environment off northern Chile (23°S)
Provedor de dados: 97
Autores: ORTLIEB,LUC; ESCRIBANO,RUBEN; FOLLEGATI,RENZO; ZUÑIGA,OSCAR; KONG,ISMAEL; RODRIGUEZ,LUIS; VALDES,JORGE; GUZMAN,NURY; IRATCHET,PAOLA.
Atmosphere-ocean interactions are particularly strong along the Chile-Peru coast and largely account for the extreme aridity of the Atacama Desert. Near the center of the driest part of this coastal desert, we found that the embayment Bahía Mejillones constitutes an unusually favorable setting for the formation and subsequent preservation of a sedimentary record of the successive oceanographic conditions of the last few thousand years. This work deals with relative abundance of various bio-indicators, including fish scales, foraminifers and phytoplankton, with a centimetre-scale resolution, in several gravity cores taken from 80 to 120 m depth, in a low-oxygen environment. We use this information to document ocean-climate changes at decadal to centennial...
Tipo: Journal article
Palavras-chave: Bioindicators; Paleoceanography; Paleoclimatology; Northern-Chile; Low-oxygen sediments.
Ano: 2000
URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2000000200002

Eocene-Pliocene deep sea ostracodes from ODP site 744A, Southern Indian Ocean
Provedor de dados: 42
Autores: Bergue,Cristianini T.; Govindan,Abiraman.
The Eocene-Pliocene deep sea ostracodes from the ODP site 744A (Kerguelen Plateau) are herein studied under the taxonomic and paleoecologic aspects. 28 species are identified, being the genera Krithe, Cytherella and Dutoitella the most diversified. A faunal threshold was recorded in the Early Oligocene, which is tentatively explained under the knowledge of the paleoceanographical studies carried out not only in the Kerguelen Plateau but also in adjacent areas. The faunal turnover and variations in both richness and abundance possibly reflect the inception of psychrosphere and the influence of hydrological changes in the preservation of carapaces. Moreover, the influence of those changes on carbonate preservation is discussed as the cause of faunal...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Cenozoic; Ostracodes; Paleoceanography; Paleozoogeography.
Ano: 2010
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652010000300021

The sea-level highstand correlated to marine isotope stage (MIS) 7 in the coastal plain of the state of Rio Grande do Sul, Brazil
Provedor de dados: 42
Autores: LOPES,RENATO P.; DILLENBURG,SERGIO R.; SCHULTZ,CESAR L.; FERIGOLO,JORGE; RIBEIRO,ANA MARIA; PEREIRA,JAMIL C.; HOLANDA,ELIZETE C.; PITANA,VANESSA G.; KERBER,LEONARDO.
The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosseliasp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline....
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Barrier II; Chuí Creek; MIS 7; Pleistocene; Paleoceanography.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000401573