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57 results on '"temperature proxy"'

51. Labrador current variability over the last 2000 years

Author

Marit-Solveig Seidenkrantz, Ioanna Bouloubassi, Myriam Khodri, Sabine Schmidt, Jesper V. Olsen, Juliette Mignot, Antoon Kuijpers, Marion Benetti, Marie-Alexandrine Sicre, Ullah Ezat, Guillaume Massé, Kaarina Weckström, Biogéochimie-Traceurs-Paléoclimat (BTP), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Paléocéanographie (PALEOCEAN), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Takuvik Joint International Laboratory ULAVAL-CNRS, Université Laval [Québec] (ULaval)-Centre National de la Recherche Scientifique (CNRS), Processus de la variabilité climatique tropicale et impacts (PARVATI), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Geological Survey of Denmark and Greenland (GEUS), Aarhus University [Aarhus], Université Laval [Québec] (ULaval)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Takuvik Joint ULaval/CNRS Laboratory, and Centre National de la Recherche Scientifique (CNRS)-Laval University [Québec]

Subjects
Alkenone, ALKENONES, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Labrador Sea, DIATOM EVIDENCE, WEST GREENLAND, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, CLIMATE VARIABILITY, MILLENNIUM, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, temperature proxy, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, ocean variability, SEA, Anomaly (natural sciences), Global warming, North Atlantic Deep Water, LATE-HOLOCENE, NORTH-ATLANTIC OSCILLATION, RECORD, Northern Annular Mode, Newfoundland, Gulf Stream, Current (stream), Geophysics, Oceanography, Arctic oscillation, last millennia, PAST 1500 YEARS, 13. Climate action, Space and Planetary Science, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Climatology, Period (geology), Geology
Abstract

The ice-loaded Labrador Current (LC) is an important component of the western North Atlantic circulation that influences the position and strength of the northern limb of the North Atlantic Current (NAC). This flow of cold and fresh Polar Waters originating from the Arctic has a marked impact on the North Atlantic climate, yet little is known about its variability beyond the instrumental period. In this study, we present the first sub-decadal alkenone-based 2000-year long sea-surface temperature (SST) records from the western Labrador Sea, a climatically crucial region at the boundary between the LC and the NAC. Our results show a clear link between the LC strength and the Northern Annular Mode (NAM), with a stronger NAM and a more vigorous LC during the Medieval Climate Anomaly (MCA). This suggests enhanced LC activity upon future global warming with implications for the Atlantic meridional overturning circulation (AMOC). (C) 2014 Elsevier B.V. All rights reserved.

Published
2014

52. Mg/Ca, B/Ca and U/Ca in shells of benthic foraminifers: Tracers of temperature and seawater carbonate chemistry

Author

Raitzsch, M., Wefer, Gerold, and Bohrmann, Gerhard

Subjects
550 Earth sciences and geology, ddc:550, trace metals, benthic foraminifers, temperature proxy, carbonate system proxy
Abstract

Mg/Ca ratios in benthic foraminiferal shells are frequently used in paleoceanographic studies to estimate past bottom water temperatures. Apart from temperature, other factors may exert additional influences on foraminiferal Mg/Ca. These include the Mg/Ca ratio of seawater, partial dissolution of shell calcite, salinity, physiological effects, and, probably of capital importance, the carbonate chemistry of seawater. In this context, the separate effects of temperature and seawater carbonate chemistry on the magnesium incorporation into benthic foraminiferal calcite are unraveled and quantified in this thesis. Further, B/Ca and U/Ca in benthic foraminifers were investigated as potential carbonate system proxies that may be used to correct for the carbonate ion effect on Mg/Ca.

Published
2008

53. Coral Li/Ca in micro-structural domains as a temperature proxy

Author

Paolo Montagna, Lopez Correa, M., Rueggeberg, A., Mcculloch, M., Rodolfo-Metalpa, R., Dullo, W. C., Ferrier-Pages, C., Freiwald, A., Henderson, G. M., Mazzoli, C., Russo, S., Silenzi, S., and Taviani, M.

Subjects
Lophelia pertusa, Li/Ca, temperature proxy, vital effect, Cladocora caespitosa
Published
2008

55. Extreme warmth and heat-stressed plankton in the tropics during the Paleocene-Eocene Thermal Maximum.

Author

Frieling J, Gebhardt H, Huber M, Adekeye OA, Akande SO, Reichart GJ, Middelburg JJ, Schouten S, and Sluijs A

Subjects
Fossils, Global Warming, Heat-Shock Response physiology, Plankton physiology
Abstract

Global ocean temperatures rapidly warmed by ~5°C during the Paleocene-Eocene Thermal Maximum (PETM; ~56 million years ago). Extratropical sea surface temperatures (SSTs) met or exceeded modern subtropical values. With these warm extratropical temperatures, climate models predict tropical SSTs >35°C-near upper physiological temperature limits for many organisms. However, few data are available to test these projected extreme tropical temperatures or their potential lethality. We identify the PETM in a shallow marine sedimentary section deposited in Nigeria. On the basis of planktonic foraminiferal Mg/Ca and oxygen isotope ratios and the molecular proxy [Formula: see text], latest Paleocene equatorial SSTs were ~33°C, and [Formula: see text] indicates that SSTs rose to >36°C during the PETM. This confirms model predictions on the magnitude of polar amplification and refutes the tropical thermostat theory. We attribute a massive drop in dinoflagellate abundance and diversity at peak warmth to thermal stress, showing that the base of tropical food webs is vulnerable to rapid warming.

Published
2017
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56. An explanation for the 18O excess in Noelaerhabdaceae coccolith calcite

Author

Hermoso, M, Minoletti, F, Aloisi, G, Bonifacie, M, McClelland, H, Labourdette, N, Renforth, P, Chaduteau, C, and Rickaby, R

Subjects
Vital effect, Geochemistry and Petrology, Carbon (CO2) limitation, fungi, Biomineralisation, QE, Oxygen isotope fractionation, Emiliania huxleyi, Gephyrocapsa oceanica, QR, Temperature proxy
Abstract

Coccoliths have dominated the sedimentary archive in the pelagic environment since the Jurassic. The biominerals produced by the coccolithophores are ideally placed to infer sea surface temperatures from their oxygen isotopic composition, as calcification in this photosynthetic algal group only occurs in the sunlit surface waters. In the present study, we dissect the isotopic mechanisms contributing to the “vital effect”, which overprints the oceanic temperatures recorded in coccolith calcite. Applying the passive diffusion model of carbon acquisition by the marine phytoplankton widely used in biogeochemical and palaeoceanographic studies, our results suggest that the oxygen isotope offsets from inorganic calcite in fast dividing species Emiliania huxleyi and Gephyrocapsa oceanica originates from the legacy of assimilated 18O-rich CO2 that induces transient isotopic disequilibrium to the internal dissolved inorganic carbon (DIC) pool. The extent to which this intracellular isotopic disequilibrium is recorded in coccolith calcite (1.5 to +3‰ over a 10 to 25°C temperature range) is set by the degree of isotopic re-equilibration between CO2 and water molecules before intracellular mineralisation. We show that the extent of re-equilibration is, in turn, set by temperature through both physiological (dynamics of the utilisation of the DIC pool) and thermodynamic (completeness of the re-equilibration of the relative 18O-rich CO2 influx) processes. At the highest temperature, less ambient aqueous CO2 is present for algal growth, and the consequence of carbon limitation is exacerbation of the oxygen isotope vital effect, obliterating the temperature signal. This culture dataset further demonstrates that the vital effect is variable for a given species/morphotype, and depends on the intricate relationship between the environment and the physiology of biomineralising algae.

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57. Assessing the reproducibility and reliability of estuarine bivalve shells (Saxidomus giganteus) for sea surface temperature reconstruction: Implications for paleoclimate studies

Author

Eddy Keppens, David P. Gillikin, Hans Ulens, Marc Elskens, Fjo De Ridder, Frank Dehairs, Willy Baeyens, Analytical and Environmental Chemistry, and Electricity

Subjects
Saxidomus, Seasonal profile, Temperature proxy, geography, geography.geographical_feature_category, biology, Coral, Paleontology, Mineralogy, Estuary, Isotope, Oxygen, Puget Sound, Oceanography, biology.organism_classification, Isotopes of oxygen, Salinity, Sea surface temperature, Isotopes of carbon, Bivalves, Carbon, Paleoclimatology, reproducibility, Ecology, Evolution, Behavior and Systematics, Geology, Earth-Surface Processes
Abstract

Studies using oxygen isotopes (d18O) of mollusk shells to determine paleotemperature need to assume water d18O values, which could severely influence calculated temperatures. We analyzed aragonitic shells of the Butter Clam, Saxidomus giganteus (DeShayes, 1839), to determine the reproducibility of the isotopic signal between individuals and to assess how precisely temperature could be calculated given known salinity and temperature. Furthermore, carbon isotopes are also investigated as an environmental proxy. The abundance of well-preserved S. giganteus shells in archeological and geological deposits in northwestern North America makes them a particularly suitable species for paleoclimate studies. Seasonally resolved stable oxygen isotope profiles in three S. giganteus shells collected from the same site in Puget Sound (Washington, USA) were well correlated. Although there were differences up to 0.58x in high resolution d18O profiles of the three shells, the difference between the average d18Oof each shell was less than half of this (0.19x) and half of what has been reported for between-colony coral variability. y13C profiles on the other hand were more complex, with shell d13C being about 2.5x lower than expected equilibrium values. However, this roughly conforms to the idea that about 10% of the shell carbon originates from metabolic CO2. Both d18O and d13C indicate that S. giganteus do not grow during periods of reduced salinity. Despite the excellent reproducibility of y18O between shells, and the fact that salinity effects were duly considered, calculated temperature still differed from instrumental temperature. Applying different salinity-d18O water relationships to average shell y18O, and considering salinity from the shell collection site and a nearby offshore station resulted in calculated average water temperatures ranging from 1.7 to 6.4 8C warmer than measured. Although we could not determine if S. giganteus precipitate their shells in isotopic equilibrium, we believe that the difficulty in predicting temperature arose from not being able to accurately determine d18O of the water at the time of shell precipitation. These data highlight the difficulties inherent to using stable isotope profiles of estuarine biogenic carbonates as environmental proxies.

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