Consulta: subjectFacets:"Alkenones"
Registros recuperados: 10
Data/hora: 06/06/2024 08:42:59

Hydrological changes in the Mediterranean Sea over the last 30,000 years
Provedor de dados: 5
Autores: Essallami, L.; Sicre, M. A.; Kallel, N.; Labeyrie, L.; Siani, G.
Sea surface temperatures were reconstructed over the last 30,000 years from alkenone paleothermometry (SST-(alk)) and planktonic foraminifera assemblages using the Modern Analog Technique (MAT) (SST-(foram)) along two cores of the Mediterranean Sea: MD84-632 (Levantine basin) and MD04-2797 (Siculo-Tunisian Strait). Oxygen isotope of planktonic foraminifera G. bulloides for core MD04-2797 and G. ruber for core MD84-632 were also determined. SST-alk in the Levantine basin indicate colder values at the Last Glacial Maximum (LGM) (similar to 14 degrees C) than earlier established from MAT, and a cooling amplitude of 6 degrees-7 degrees C, comparable to the central Mediterranean Sea. Climatic events such as the Younger Dryas (YD) and Heinrich events 1 and 2 (H1...
Tipo: Text
Palavras-chave: Paleoclimate; Glacial; Mediterranean; Alkenones; Foraminifera; Marine core.
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00208/31954/30378.pdf

Sea surface temperature variability in the Norwegian Sea during the late Pliocene linked to subpolar gyre strength and radiative forcing
Provedor de dados: 5
Autores: Bachem, Paul E.; Risebrobakken, Bjorg; Mcclymont, Erin L.
The mid-Piacenzian warm period (3.264-3.025 Ma) of the Pliocene epoch has been proposed as a possible reference for future warm climate states. However, there is significant disagreement over the magnitude of high latitude warming between data and models for this period of time, raising questions about the driving mechanisms and responsible feedbacks. We have developed a new set of orbital-resolution alkenone-based sea surface temperature (SST) and ice rafted debris (IRD) records from the Norwegian Sea spanning 3.264-3.14 Ma. The SSTs in the Norwegian Sea were 2-3 degrees C warmer than the Holocene average, likely caused by the radiative effect of higher atmospheric CO2 concentrations. There is notable obliquity-driven SST variability with a range of 4...
Tipo: Text
Palavras-chave: Pliocene; Norwegian Sea; ODP Site 642; Alkenones; SST; Subpolar gyre.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00421/53230/83372.pdf

Holocene sea-surface temperature variability in the Chilean fjord region
Provedor de dados: 5
Autores: Caniupan, Magaly; Lamy, Frank; Lange, Carina B.; Kaiser, Jerome; Kilian, Rolf; Arz, Helge W.; Leon, Tania; Mollenhauer, Gesine; Sandoval, Susana; De Pol-holz, Ricardo; Pantoja, Silvio; Wellner, Julia; Tiedemann, Ralf.
Here we provide three new Holocene (11-0 cal ka BP) alkenone-derived sea surface temperature (SST) records from the southernmost Chilean fjord region (50-53 degrees S). SST estimates may be biased towards summer temperature in this region, as revealed by a large set of surface sediments. The Holocene records show consistently warmer than present-day SSTs except for the past similar to 0.6 cal ka BP. However, they do not exhibit an early Holocene temperature optimum as registered further north off Chile and in Antarctica. This may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea-level stands, enhanced advection of colder and fresher inner fjord waters, and stronger westerly winds. During...
Tipo: Text
Palavras-chave: Holocene; Alkenones; Sea-surface temperature; Fjords; Chile.
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00290/40088/39292.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

Postglacial paleoceanography of the western Barents Sea: Implications for alkenone-based sea surface temperatures and primary productivity
Provedor de dados: 5
Autores: Łącka, Magdalena; Cao, Min; Rosell-melé, Antoni; Pawłowska, Joanna; Kucharska, Małgorzata; Forwick, Matthias; Zajączkowski, Marek.
The increasing influence of Atlantic Water (AW) in the Barents Sea, a process known as “Atlantification”, is gradually decreasing sea ice cover in the region. Ongoing global climate warming is likely to be one of its drivers, but to further understand the role of natural variability and the biogeochemical impacts of the inflow of AW into the western Barents Sea, we reconstructed sea surface temperatures (SSTs) and primary productivity in Storfjordrenna, a climatically sensitive area south of Spitsbergen, between approximately 13,950 cal yr BP and 1300 cal yr BP. The alkenone proxy has been applied to reconstruct SSTs, and the alkenone accumulation rate in marine sediments has been used to infer changes in primary productivity. Our data show that the SST...
Tipo: Text
Palavras-chave: Alkenones; Stratification; Holocene; Sea ice decrease; Global warming; North Atlantic Current; Arctic.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00585/69740/67629.pdf

Antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore South Australia
Provedor de dados: 5
Autores: Calvo, Eva; Pelejero, Carles; De Deckker, Patrick; Logan, Graham A.
Comparison of ice cores from Greenland and Antarctica shows an asynchronous two-step warming at these high latitudes during the Last Termination. However, the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the Southern Hemisphere. New data from a marine core collected off South Australia (similar to 36 degrees S) allows a detailed reconstruction of sea-surface temperatures over the Last Termination. This confirms the existence of an Antarctic-type deglacial pattern and shows no indication of cooling associated with the Northern Hemisphere YD event. The SST record also provides a new comparison with the more extensive paleoclimatic data available from continental Australia. This shows a...
Tipo: Text
Palavras-chave: Alkenones; Deglaciation; Southern Hemisphere.
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00235/34647/33013.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

Millennial-scale sea surface temperature and Patagonian Ice Sheet changes off southernmost Chile (53 degrees S) over the past similar to 60 kyr
Provedor de dados: 5
Autores: Caniupan, M.; Lamy, F.; Lange, C. B.; Kaiser, J.; Arz, H.; Kilian, R.; Baeza Urrea, O.; Aracena, C.; Hebbeln, D.; Kissel, C.; Laj, C.; Mollenhauer, G.; Tiedemann, R.
Glacial millennial-scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well-dated and high resolution sediment records. Here we present new surface water records from sediment core MD07-3128 recovered at 53 degrees S off the Pacific entrance of the Strait of Magellan. The alkenone-derived sea surface temperature (SST) record reveals a very strong warming of ca. 8 C over the last Termination and substantial millennial-scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (delta(18)O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial-scale SST fluctuations are...
Tipo: Text
Palavras-chave: Patagonian Ice Sheet; Alkenones; Ice rafted debris; Millennial-scale changes; Southeast Pacific.
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00214/32516/31000.pdf

Global temperature calibration of the alkenone unsaturation index (U(37)(K ')) in surface waters and comparison with surface sediments
Provedor de dados: 5
Autores: Conte, Mh; Sicre, Ma; Ruhlemann, C; Weber, Jc; Schulte, S; Schulz-bull, D; Blanz, T.
[1] In this paper, we compile the current surface seawater C(37) alkenone unsaturation (U(37)(K')) measurements ( n = 629, - 1 to 30 degrees C temperature range) to derive a global, field-based calibration of U(37)(K') with alkenone production temperature. A single nonlinear "global'' surface water calibration of U(37)(K') accurately predicts alkenone production temperatures over the diversity of modern-day oceanic environments and alkenone-synthesizing populations (T = - 0.957 + 54.293(U(37)(K')) - 52.894(U(37)(K'))(2) + 28.321(U(37)(K'))(3), r(2) = 0.97, n = 567). The mean standard error of estimation is 1.2 degrees C with insignificant bias in estimated production temperature among the different ocean regions sampled. An exception to these trends is...
Tipo: Text
Palavras-chave: Alkenones; Paleoproxies; Sea surface temperature; UK ' 37.
Ano: 2006
URL: https://archimer.ifremer.fr/doc/00239/34978/33474.pdf

Modern sedimentation in the Cabo Frio upwelling system, Southeastern Brazilian shelf
Provedor de dados: 42
Autores: Mahiques,Michel M. de; Bícego,Marcia C.; Silveira,Ilson C.A.; Sousa,Silvia H.M.; Lourenço,Rafael A.; Fukumoto,Marina M.
The analyses of Uk'37 paleotemperatures and sedimentological parameters in box cores from the Cabo Frio upwelling zone, southeastern Brazil, were used to understand the modern sedimentation as well as to evaluate the role played by the upwelling process in the sedimentary patterns. Three box-cores located closer to the upwelling area show a general trend of cooling waters taking place in the last 700 years. Since the present upwelling is dependent on local and remote wind regime, a phase of dominating NE winds favors a more effective upward transport of the cold thermocline level South Atlantic CentralWater towards the coast. The intensification in the upwelling regime for the last ca. 700 years can be associated with the strengthening of the NE winds off...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Sedimentation; Alkenones; Bulk organic matter; Upwelling; Brazil; South Atlantic.
Ano: 2005
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652005000300013