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  • Artikel  (9)
  • 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability
  • Salinity
  • Nature Publishing Group (NPG)  (5)
  • American Meteorological Society  (3)
  • Agu  (1)
  • MDPI Publishing
  • 2005-2009  (9)
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  • Artikel  (9)
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  • 1
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    Stability against freezing of aqueous solutions on early Mars (2009)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2009-05-22
    Beschreibung: Many features of the Martian landscape are thought to have been formed by liquid water flow and water-related mineralogies on the surface of Mars are widespread and abundant. Several lines of evidence, however, suggest that Mars has been cold with mean global temperatures well below the freezing point of pure water. Martian climate modellers considering a combination of greenhouse gases at a range of partial pressures find it challenging to simulate global mean Martian surface temperatures above 273 K, and local thermal sources cannot account for the widespread distribution of hydrated and evaporitic minerals throughout the Martian landscape. Solutes could depress the melting point of water in a frozen Martian environment, providing a plausible solution to the early Mars climate paradox. Here we model the freezing and evaporation processes of Martian fluids with a composition resulting from the weathering of basalts, as reflected in the chemical compositions at Mars landing sites. Our results show that a significant fraction of weathering fluids loaded with Si, Fe, S, Mg, Ca, Cl, Na, K and Al remain in the liquid state at temperatures well below 273 K. We tested our model by analysing the mineralogies yielded by the evolution of the solutions: the resulting mineral assemblages are analogous to those actually identified on the Martian surface. This stability against freezing of Martian fluids can explain saline liquid water activity on the surface of Mars at mean global temperatures well below 273 K.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fairen, Alberto G -- Davila, Alfonso F -- Gago-Duport, Luis -- Amils, Ricardo -- McKay, Christopher P -- England -- Nature. 2009 May 21;459(7245):401-4. doi: 10.1038/nature07978.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, California 94035, USA. alberto.g.fairen@nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19458717" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmospheric Pressure ; Carbon Dioxide/analysis ; Extraterrestrial Environment/*chemistry ; *Freezing ; Ice/analysis ; *Mars ; Partial Pressure ; Salinity ; Transition Temperature ; Volatilization ; Water/*chemistry
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 2
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    2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool (2009)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2009-08-29
    Beschreibung: Northern Hemisphere surface temperature reconstructions suggest that the late twentieth century was warmer than any other time during the past 500 years and possibly any time during the past 1,300 years (refs 1, 2). These temperature reconstructions are based largely on terrestrial records from extra-tropical or high-elevation sites; however, global average surface temperature changes closely follow those of the global tropics, which are 75% ocean. In particular, the tropical Indo-Pacific warm pool (IPWP) represents a major heat reservoir that both influences global atmospheric circulation and responds to remote northern high-latitude forcings. Here we present a decadally resolved continuous sea surface temperature (SST) reconstruction from the IPWP that spans the past two millennia and overlaps the instrumental record, enabling both a direct comparison of proxy data to the instrumental record and an evaluation of past changes in the context of twentieth century trends. Our record from the Makassar Strait, Indonesia, exhibits trends that are similar to a recent Northern Hemisphere temperature reconstruction. Reconstructed SST was, however, within error of modern values from about ad 1000 to ad 1250, towards the end of the Medieval Warm Period. SSTs during the Little Ice Age (approximately ad 1550-1850) were variable, and approximately 0.5 to 1 degrees C colder than modern values during the coldest intervals. A companion reconstruction of delta(18)O of sea water-a sea surface salinity and hydrology indicator-indicates a tight coupling with the East Asian monsoon system and remote control of IPWP hydrology on centennial-millennial timescales, rather than a dominant influence from local SST variation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Oppo, Delia W -- Rosenthal, Yair -- Linsley, Braddock K -- England -- Nature. 2009 Aug 27;460(7259):1113-6. doi: 10.1038/nature08233.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. doppo@whoi.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19713927" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Atmosphere/analysis ; Calibration ; History, 15th Century ; History, 16th Century ; History, 17th Century ; History, 18th Century ; History, 19th Century ; History, 20th Century ; History, 21st Century ; History, Ancient ; History, Medieval ; Ice Cover ; India ; Indonesia ; Oceans and Seas ; Oxygen Isotopes ; Pacific Ocean ; Plankton/metabolism ; Rain ; Records as Topic ; Salinity ; Seasons ; Seawater/*analysis ; *Temperature ; Time Factors ; Tropical Climate ; Weather
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 3
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    Migration of the subtropical front as a modulator of glacial climate (2009)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2009-07-17
    Beschreibung: Ice cores extracted from the Antarctic ice sheet suggest that glacial conditions, and the relationship between isotopically derived temperatures and atmospheric PCO(2) have been constant over the last 800,000 years of the Late Pleistocene epoch. But independent lines of evidence, such as the extent of Northern Hemisphere ice sheets, sea level and other temperature records, point towards a fluctuating severity of glacial periods, particularly during the more extreme glacial stadials centred around 340,000 and 420,000 years ago (marine isotope stages 10 and 12). Previously unidentified mechanisms therefore appear to have mediated the relationship between insolation, CO(2) and climate. Here we test whether northward migration of the subtropical front (STF) off the southeastern coast of South Africa acts as a gatekeeper for the Agulhas current, which controls the transport of heat and salt from the Indo-Pacific Ocean to the Atlantic Ocean. Using a new 800,000-year record of sea surface temperature and ocean productivity from ocean sediment core MD962077, we demonstrate that during cold stadials (particularly marine isotope stages 10 and 12), productivity peaked and sea surface temperature was up to 6 degrees C cooler than modern temperatures. This suggests that during these cooler stadials, the STF moved northward by up to 7 degrees latitude, nearly shutting off the Agulhas current. Our results, combined with faunal assemblages from the south Atlantic show that variable northwards migration of the Southern Hemisphere STF can modulate the severity of each glacial period by altering the strength of the Agulhas current carrying heat and salt to the Atlantic meridional overturning circulation. We show hence that the degree of northwards migration of the STF can partially decouple global climate from atmospheric partial pressure of carbon dioxide, P CO(2), and help to resolve the long-standing puzzle of differing glacial amplitudes within a consistent range of atmospheric PCO(2).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bard, Edouard -- Rickaby, Rosalind E M -- England -- Nature. 2009 Jul 16;460(7253):380-3. doi: 10.1038/nature08189.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉CEREGE (UMR 6635), College de France, University Paul-Cezanne Aix-Marseille, CNRS, IRD, Europole de l'Arbois BP 80, 13545 Aix-en-Provence Cedex 4, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19606147" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Amoeba/metabolism ; Animals ; Antarctic Regions ; Atlantic Ocean ; Atmosphere/chemistry ; Carbon Dioxide/metabolism ; *Climate ; Cold Climate ; Cold Temperature ; Geologic Sediments/microbiology ; *Ice Cover ; Indian Ocean ; Oxygen Isotopes ; Pacific Ocean ; Partial Pressure ; Plankton/metabolism ; Salinity ; Seawater/chemistry ; South Africa ; Tropical Climate ; *Water Movements
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 4
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    Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies (2009)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2009-11-27
    Beschreibung: The transport of warm and salty Indian Ocean waters into the Atlantic Ocean-the Agulhas leakage-has a crucial role in the global oceanic circulation and thus the evolution of future climate. At present these waters provide the main source of heat and salt for the surface branch of the Atlantic meridional overturning circulation (MOC). There is evidence from past glacial-to-interglacial variations in foraminiferal assemblages and model studies that the amount of Agulhas leakage and its corresponding effect on the MOC has been subject to substantial change, potentially linked to latitudinal shifts in the Southern Hemisphere westerlies. A progressive poleward migration of the westerlies has been observed during the past two to three decades and linked to anthropogenic forcing, but because of the sparse observational records it has not been possible to determine whether there has been a concomitant response of Agulhas leakage. Here we present the results of a high-resolution ocean general circulation model to show that the transport of Indian Ocean waters into the South Atlantic via the Agulhas leakage has increased during the past decades in response to the change in wind forcing. The increased leakage has contributed to the observed salinification of South Atlantic thermocline waters. Both model and historic measurements off South America suggest that the additional Indian Ocean waters have begun to invade the North Atlantic, with potential implications for the future evolution of the MOC.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Biastoch, A -- Boning, C W -- Schwarzkopf, F U -- Lutjeharms, J R E -- England -- Nature. 2009 Nov 26;462(7272):495-8. doi: 10.1038/nature08519.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Leibniz-Institut fur Meereswissenschaften, Dusternbrooker Weg 20, 24105 Kiel, Germany. abiastoch@ifm-geomar.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19940923" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Africa ; Atlantic Ocean ; Computer Simulation ; Foraminifera ; Indian Ocean ; Salinity ; Seawater/*analysis/chemistry ; Temperature ; *Water Movements ; *Wind
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 5
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    Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris (2009)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2009-07-17
    Beschreibung: Oceanic sediments from long cores drilled on the Lomonosov ridge, in the central Arctic, contain ice-rafted debris (IRD) back to the middle Eocene epoch, prompting recent suggestions that ice appeared in the Arctic about 46 million years (Myr) ago. However, because IRD can be transported by icebergs (derived from land-based ice) and also by sea ice, IRD records are restricted to providing a history of general ice-rafting only. It is critical to differentiate sea ice from glacial (land-based) ice as climate feedback mechanisms vary and global impacts differ between these systems: sea ice directly affects ocean-atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity. An earlier report assumed that sea ice was prevalent in the middle Eocene Arctic on the basis of IRD, and although somewhat preliminary supportive evidence exists, these data are neither comprehensive nor quantified. Here we show the presence of middle Eocene Arctic sea ice from an extraordinary abundance of a group of sea-ice-dependent fossil diatoms (Synedropsis spp.). Analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of IRD at this time. Together with new information on cosmopolitan diatoms and existing IRD records, our data strongly suggest a two-phase establishment of sea ice: initial episodic formation in marginal shelf areas approximately 47.5 Myr ago, followed approximately 0.5 Myr later by the onset of seasonally paced sea-ice formation in offshore areas of the central Arctic. Our data establish a 2-Myr record of sea ice, documenting the transition from a warm, ice-free environment to one dominated by winter sea ice at the start of the middle Eocene climatic cooling phase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stickley, Catherine E -- St John, Kristen -- Koc, Nalan -- Jordan, Richard W -- Passchier, Sandra -- Pearce, Richard B -- Kearns, Lance E -- England -- Nature. 2009 Jul 16;460(7253):376-9. doi: 10.1038/nature08163.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉[1] Department of Geology, University of Tromso, N-9037 Tromso, Norway [2] Norwegian Polar Institute, Polar Environmental Centre, N-9296 Tromso, Norway.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19606146" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Arctic Regions ; *Cold Climate ; Diatoms/chemistry/*isolation & purification/ultrastructure ; Fossils ; Geologic Sediments/microbiology ; History, Ancient ; Hydrogen-Ion Concentration ; Ice Cover/*chemistry/*microbiology ; Microscopy, Electron, Scanning ; Oceans and Seas ; Principal Component Analysis ; Salinity ; Seawater/chemistry ; Silicon Dioxide/analysis
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 6
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    Aegean Sea Water Masses during the Early Stages of the Eastern Mediterranean Climatic Transient (2007)
    American Meteorological Society
    Details
    Publikationsdatum: 2021-06-08
    Beschreibung: The Aegean water masses and circulation structure are studied via two large-scale surveys performed during the late winters of 1988 and 1990 by the R/V Yakov Gakkel of the former Soviet Union. The analysis of these data sheds light on the mechanisms of water mass formation in the Aegean Sea that triggered the outflow of Cretan Deep Water (CDW) from the Cretan Sea into the abyssal basins of the eastern Mediterranean Sea (the so-called Eastern Mediterranean Transient). It is found that the central Aegean Basin is the site of the formation of Aegean Intermediate Water, which slides southward and, depending on their density, renews either the intermediate or the deep water of the Cretan Sea. During the winter of 1988, the Cretan Sea waters were renewed mainly at intermediate levels, while during the winter of 1990 it was mainly the volume of CDW that increased. This Aegean water mass redistribution and formation process in 1990 differed from that in 1988 in two major aspects: (i) during the winter of 1990 the position of the front between the Black Sea Water and the Levantine Surface Water was displaced farther north than during the winter of 1988 and (ii) heavier waters were formed in 1990 as a result of enhanced lateral advection of salty Levantine Surface Water that enriched the intermediate waters with salt. In 1990 the 29.2 isopycnal rose to the surface of the central basin and a large volume of CDW filled the Cretan Basin. It is found that, already in 1988, the 29.2 isopycnal surface, which we assume is the lowest density of the CDW, was shallower than the Kassos Strait sill and thus CDW egressed into the Eastern Mediterranean.
    Beschreibung: Published
    Beschreibung: 1841-1859
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): Aegean Sea ; Water Masses ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 7
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    Effects of NAO variability on the North Atlantic Ocean circulation (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: The ocean response to an idealised North Atlantic Oscillation-like wind stress is evaluated as a function of the atmospheric forcing frequency. In order to elucidate the relationship between internal and forced variability, the NAO is modulated with two specific timescales, 10 and 50 years, which characterise the spectrum of the system’s internal variability. Different timescales of atmospheric variability select distinct sea surface temperature (SST) and large scale circulation patterns. Under a 50 year NAO forcing period, a lagged SST response is excited in the Gulf Stream extension region, which is consistent with the spinup of the gyre circulation. The thermohaline circulation varies in phase with the NAO and shows a strong sensitivity to the forcing frequency: a dipole mode of the overturning is excited by a 10 year modulation of the NAO, while an enhanced overturning response emerges under a 50 year NAO. With low enough lateral mixing the ocean exhibits an irregular response to a regular NAO-like forcing.
    Beschreibung: Published
    Beschreibung: L02612
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): NAO ; Ocean circulation ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Using Temperature–Salinity Relations in a Global Ocean Implementation of a Multivariate Data Assimilation Scheme (2008)
    American Meteorological Society
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: In this paper results from the application of an ocean data assimilation (ODA) system, combining a multivariate reduced-order optimal interpolator (OI) scheme with a global ocean general circulation model (OGCM), are described. The present ODA system, designed to assimilate in situ temperature and salinity observations, has been used to produce ocean reanalyses for the 1962–2001 period. The impact of assimilating observed hydrographic data on the ocean mean state and temporal variability is evaluated. A special focus of this work is on the ODA system skill in reproducing a realistic ocean salinity state. Results from a hierarchy of different salinity reanalyses, using varying combinations of assimilated data and background error covariance structures, are described. The impact of the space and time resolution of the background error covariance parameterization on salinity is addressed.
    Beschreibung: This work has been funded by the ENACT Project (Contract EVK2-CT2001-00117) for A. Bellucci and P. Di Pietro, and partially by the ENSEMBLES Project (Contract GOCE-CT-2003-505539) for A. Bellucci.
    Beschreibung: Published
    Beschreibung: 3785-3807
    Beschreibung: 3.7. Dinamica del clima e dell'oceano
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): ocean modelling ; data assimilation ; reanalysis ; upper ocean variability ; temperature ; Salinity ; 03. Hydrosphere::03.01. General::03.01.04. Ocean data assimilation and reanalysis
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 9
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    Interannual to Decadal Climate Predictability in the North Atlantic: A Multi-Model-Ensemble Study (2007)
    American Meteorological Society
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: Ensemble experiments are performed with five coupled atmosphere–ocean models to investigate the potential for initial-value climate forecasts on interannual to decadal time scales. Experiments are started from similar model-generated initial states, and common diagnostics of predictability are used. We find that variations in the ocean meridional overturning circulation (MOC) are potentially predictable on interannual to decadal time scales, a more consistent picture of the surface temperature impact of decadal variations in the MOC is now apparent, and variations of surface air temperatures in the North Atlantic Ocean are also potentially predictable on interannual to decadal time scales, albeit with potential skill levels that are less than those seen for MOC variations. This intercomparison represents a step forward in assessing the robustness of model estimates of potential skill and is a prerequisite for the development of any operational forecasting system.
    Beschreibung: Published
    Beschreibung: 1195-1203
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): Decadal Climate ; North Atlantic ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models ; 03. Hydrosphere::03.02. Hydrology::03.02.05. Models and Forecasts ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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