http://hdl.handle.net/2122/89 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/5694 Titolo: Evidence for Obliquity Forcing of Glacial Termination II<br/><br/>Autori: Drysdale, R. N.; Environmental and Climate Change Group, University of Newcastle, Callaghan, New South Wales 2308, Australia; Hellstrom, J. C.; School of Earth Sciences, University of Melbourne, Parkville, Victoria 2010, Australia; Zanchetta, G.; Department of Earth Sciences, University of Pisa, Pisa 56100, Italy; Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Pisa, Italy; IGG-CNR, Pisa, Italy; Fallick, A. E.; Scottish Universities Environmental Research Centre, East Kilbride G75 0GF, UK.; Sanchez-Goni, M. F.; EPHE, UMR CNRS 5805 EPOC, Université Bordeaux 1, 33405 Talence, France.; Couchoud, I.; Environmental and Climate Change Group, University of Newcastle, Callaghan, New South Wales 2308, Australia; McDonald, J.; Environmental and Climate Change Group, University of Newcastle, Callaghan, New South Wales 2308, Australia; Maas, R.; School of Earth Sciences, University of Melbourne, Parkville, Victoria 2010, Australia; Lohmann, G.; Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.; Isola, I; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia<br/><br/>Abstract: Variations in the intensity of high-latitude Northern Hemisphere summer insolation, driven largely by precession of the equinoxes, are widely thought to control the timing of Late Pleistocene glacial terminations. However, recently it has been suggested that changes in Earth’s obliquity may be a more important mechanism. We present a new speleothem-based North Atlantic marine chronology that shows that the penultimate glacial termination (Termination II) commenced 141,000 ± 2500 years before the present, too early to be explained by Northern Hemisphere summer insolation but consistent with changes in Earth’s obliquity. Our record reveals that Terminations I and II are separated by three obliquity cycles and that they started at near-identical obliquity phases. Fri, 18 Sep 2009 00:00:00 GMT http://hdl.handle.net/2122/4355 Titolo: Impact of extreme CO2 levels on tropical climate: A CGCM study<br/><br/>Autori: Cherchi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Navarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia<br/><br/>Abstract: A coupled general circulation model has been used to perform a set of experiments with high CO2 concentration (2, 4, 16 times the present day mean value). The experiments have been analyzed to study the response of the climate system to strong radiative forcing in terms of the processes involved in the adjustment at the ocean-atmosphere interface. The analysis of the experiments revealed a non-linear response of the mean state of the atmosphere and ocean to the increase in the carbon dioxide concentration. In the 16xCO2 experiment the equilibrium at the ocean-atmosphere interface is characterized by an atmosphere with a shut off of the convective precipitation in the tropical Pacific sector, associated with air warmer than the ocean below. A cloud feedback mechanism is found to be involved in the increased stability of the troposphere. In this more stable condition the mean total precipitation is mainly due to large-scale moisture flux even in the tropics. In the equatorial Pacific Ocean the zonal temperature gradient of both surface and sub-surface waters is significantly smaller in the 16xCO2 experiment than in the control experiment. The thermocline slope and the zonal wind stress decrease as well. When the CO2 concentration increases by about two and four times with respect to the control experiment there is an intensification of El Nino. On the other hand, in the experiment with 16 times the present-day value of CO2, the Tropical Pacific variability weakens, suggesting the possibility of the establishment of permanent warm conditions that look like the peak of El Nino. Thu, 15 May 2008 00:00:00 GMT http://hdl.handle.net/2122/4165 Titolo: EFFECTS OF ENERGETIC SOLAR PARTICLES ON OZONE AND MINOR ATMOSPHERIC COMPONENTS INSIDE THE POLAR REGIONS<br/><br/>Autori: Damiani, A.; INAF-IFSI<br/><br/>Abstract: Solar activity influences the Earth’s environment, in particular the atmosphericozone, by the direct output of the e.m. radiation or through the variability of theincoming cosmic ray flux (solar and galactic particles). Especially energetic particles,arising from huge explosions on the Sun’s surface, travel in the interplanetarymedium and, if the circumstances were favorable, they could enter the terrestrialatmosphere (driven by the geomagnetic field lines of our planet) and reach the polarcap regions (geomagnetic latitude > 60°). There, they provide additional externalenergy and are able to produce ionizations, dissociations, dissociative ionizationsand excitations phenomena by interacting with the minor constituents. The inducedchanges are not confined to the ion chemistry but also to the neutral components. Inthis way a rise of the concentration of HOx and NOx species and the triggering ofcatalytic cycles which lead to short (hours) and medium (days) term ozonedestruction occur. Finally, also no-reactive reservoir species (e.g., HNO3, HCl, HOCl)are involved in these processes and endure large variations.The present thesis highlights the chemical variability of the middle atmosphereduring and after some Solar Energetic Particle (SEP) events recorded during thecurrent solar cycle. Special attention has been paid to the relationship betweenozone and HOx data (retrieved from the Microwave Limb Sounder of EOS AURAsatellite) for four events referred to 2005. The HOx data, recorded for the first timeduring the intense ionization caused by the SEP flux, have pointed out some featuresrelated to these phenomena not wholly captured by the current theoretical models. Inaddition, they have highlighted that the HOx rise is able to destroy the so-called thirdozone peak at the polar latitudes of the winter hemisphere and it occurs also duringmedium intensity events. Besides, the analyses of January 2005 SEP events haveshown that the changes on the hydrogen species leaded to variability in theconcentration and partitioning of chlorine family, not discernible in the summerhemisphere. Further, the use of data coming from the HALOE instrument, referred toSEP events occurred in July 2000 and April 2002, has in short confirmed pastexperimental results. Finally, the study of a little SEP event occurred during May 2003has pointed out that SEP events are not the unique ionization source inside the polarlatitudes during the winter. Sat, 01 Dec 2007 00:00:00 GMT http://hdl.handle.net/2122/3982 Titolo: Space weather and RF communications: Monitoring and modelling<br/><br/>Autori: Cander, L. R.; Rutherford Appleton Laboratory, Space Science & Technology Department, Radio Communications Research Unit, Chilton, Didcot, Oxon OX11 0QX, UK; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: At the beginning of the new millennium, ionospheric physics and its application in new technologies are at a point of significant change and new development.Ionospheric studies in the past found application in the traditional areas of broadcast and terrestrial radio communications. It has become clear, in recent years, that an understanding of the ionosphere, as a part of the upper atmosphere, is central to the design of manymodern communication, navigation and positioning systems. An important additional role has also been recognized in the areas of space weather science and services.This issue of the Journal of Atmospheric and Solar-Terrestrial Physics collects selected contributions presented at the Solar-Terrestrial Sciences session ST14 on"Space weather and RF communications: monitoring and modelling" held during the first General Assembly of the European Geosciences Union (Nice, France, 25–30 April 2004).<br/><br/>Descrizione: Preface to Journal of Atmospheric and Solar-Terrestrial Physics 67 (2005) Mon, 01 Aug 2005 00:00:00 GMT http://hdl.handle.net/2122/2796 Titolo: Degassing of gaseous (elemental and reactive) and particulate mercury from Mount Etna volcano (Southern Italy)<br/><br/>Autori: Bagnato, E.; Università di Palermo, Dipartimento CFTA; Aiuppa, A.; Università di Palermo, Dipartimento CFTA; Parello, F.; Università di Palermo, Dipartimento CFTA; Calabrese, S.; Università di Palermo, Dipartimento CFTA; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Mather, T. A.; Department of Earth Sciences, University of Oxford, UK; McGonigle, A. J. S.; Department of Geography, University of Sheffield, UK; Pyle, D. M.; Department of Earth Sciences, University of Oxford, UK; Wängberg, I.; IVL-Swedish Environmental Research Institute, Göteborg, Sweden<br/><br/>Abstract: There is an urgent need to better constrain the global rates of mercury degassing from natural sources, including active volcanoes. Hitherto, estimates of volcanic fluxes have been limited by the poorly-determined speciation of Hg in volcanic emissions. Here, we present a systematic characterisation of mercury partitioning between gaseous (Hg(g)) and particulate (Hg(p)) forms in the volcanic plume of Mount Etna, the largest open-vent passively degassing volcano on Earth. We demonstrate that mercury transport is predominantly in the gas-phase, with a mean Hg(p)/Hg(g) ratio of ∼0.01 by mass. We also present the first simultaneous measurement of divalent gaseous mercury (HgII(g)) and total gaseous mercury (Hg(g)) in a volcanic plume, which suggests that Hg0(g) is the prevalent form of mercury in this context. These data are supported by the results of model simulations, carried out with HSC thermodynamic software. Based on a mean ‘bulk plume’ Hg/SO2 mass ratio of 8.7×10-6, and a contemporaneous volcanic SO2 flux of 0.8 Mt·yr-1, we estimate an Hg emission rate from Mt. Etna during passive degassing of 5.4 t·y-1 (range, 1.1-10 t·y-1). This corresponds to ~0.6% of global volcanic Hg emissions, and about 5% of Hg released from industrial activities in the Mediterranean area. Thu, 01 Nov 2007 00:00:00 GMT http://hdl.handle.net/2122/2583 Titolo: Aspects of stratospheric long-term changes induced by ozone depletion<br/><br/>Autori: Cagnazzo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Claud, C.; Laboratoire de Me´ te´ orologie Dynamique du CNRS, Institut Pierre et Simon Laplace (IPSL), Ecole Polytechnique; Hare, S.; Department of Meteorology, University of Reading, Earley Gate<br/><br/>Abstract: The effect of the stratospheric ozone depletionon the thermal and dynamical structure of the middleatmosphere is assessed using two 5-member ensemblesof transient GCM simulations; one including lineartrends in ozone, the other not, for the 1980–1999 period.Simulated temperatures and observations are in goodagreement in terms of mean values, autocorrelations andcross correlations. Annual-mean and seasonal temperaturetrends have been calculated using the same statisticalanalysis. Simulations show that ozone trends areresponsible for reduced wave activity in the Arctic lowerstratosphere in February and March, confirming boththe role of dynamics in controlling March temperaturesand a recently proposed mechanism whereby Arcticozone depletion causes the reduction in wave activityentering the lower stratosphere. Changes in wave activityare consistent with an intensification of the polarvortex at the time of ozone depletion and with a weakenedBrewer–Dobson circulation: A decrease of thedynamical warming/cooling associated with thedescending/ascending branch of the wintertime meanresidual circulation at high/low latitudes has been obtainedthrough the analysis of temperature observations(1980–1999). Ozone is responsible of about one third ofthe decrease of this dynamical cooling at high latitudes.An increase in the residual mean circulation is seen inthe observations for the 1965–1980 period. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2122/2561 Titolo: A possible relationship between the Arctic Oscillation Index and atmosphere-triggered interannual long-wavelength<br/><br/>Autori: Lentini, G.; Universit`a di Milano - Milan, Italy; Maugeri, M.; Universit`a di Milano - Milan, Italy; Devoti, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Albertella, A.; Politecnico di Milano - Milan, Italy; Sabadini, R.; Universit`a di Milano - Milan, Italy<br/><br/>Abstract: A host of geophysical processes contribute to temporal variationsin the low-degree zonal harmonics of the Earth’s gravity field. The present paperfocuses on atmosphere-based mass redistributions using global surface pressure datafrom the NOAA Climate Diagnostics Center for the period 1980-2002. We computedatmosphere-triggered temporal variations of the Earth’s low-degree zonal gravitationalcoefficients Jl (l = 2 : 4). Such atmosphere-triggered ΔJl(t) are comparedwith the Arctic Oscillation Index (AOI) and with the observed ΔJl(t) computed bythe Italian Space Agency (ASI) so as to investigate a possible coupling. We showthat there is a significant agreement between the AOI and atmosphere-triggeredΔJl(t), as well as a particularly interesting correlation between the winter ΔJl(t)series and the AOI active season series. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2122/2534 Titolo: Physiography and tectonic setting of the subglacial lake district between Vostok and Belgica Subglacial Highlands (Antartica)<br/><br/>Autori: Tabacco, I.; Universit`a degli Studi di Milano, Dip. Scienze della Terra, Sez. Geofisica,; Cianfarra, P.; Universit`a degli Studi Roma Tre, Dip. Scienze Geologiche,; Forieri, A.; Universit`a degli Studi di Milano, Dip. Scienze della Terra, Sez. Geofisica,; Salvini, F.; Universit`a degli Studi Roma Tre, Dip. Scienze Geologiche,; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: We present the interpretation of 11 radio echo-sounding (RES) missions carried out over theVostok–Dome Concordia region during the Italian Antarctic expeditions in the period 1995–2001. The extension and the density of the radar data in the surveyed area allowed to reconstructa reliable subglacial morphology and to identify four relevant morphological structures namely:the Aurora trench, the Concordia trench, the Concordia ridge and the South Hills. Thesestructures show evidence compatible with the presence of tectonic features. Morphologicalconsiderations indicate their development in Cenozoic time. Hybrid cellular automata (HCA)-based numerical modelling allowed to justify a possible role played by the tectonics of theAurora and Concordia trench evolution. This was accomplished by matching the bed profilesalong opportunely projected sections with the modelled surfaces as derived by the activity ofnormal faults with variable surfaces within the continental crust. The Vostok–Dome C regionis characterized by a large number of subglacial lakes. From the analysis of basal reflectedpower echo, we identified 14 new lakes and obtained information about their physiography aswell as their possible relations with tectonics.We propose a grouping of subglacial lakes on thebase of their physiography and geological setting, namely relief lakes, basin lakes and trenchlakes. Relief lakes located in the Belgica subglacial highlands and are characterized by sharpand steep symmetric edges, suggesting a maximum water depth of the order of 100 m. Theirorigin may well relate to localized, positive geothermal flux anomalies. Basin lakes locatedin the Vincennes subglacial basin and are characterized by wider dimension that allow thedevelopment of well-defined, flat ice surface anomalies. Trench lakes characterize the Auroraand Concordia trenches as the possible effect of normal fault activity.Key words: Antarctica, HCA modelling, radio echo sounding, subglacial Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2122/2492 Titolo: Isotopic composition of the precipitations in the central Mediterranean: origin marks and orographic precipitation effects<br/><br/>Autori: Liotta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Favara, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Valenza, M.; Dipartimento di Chimica e Fisica della Terra, Universita` degli Studi di Palermo, Palermo, Italy.<br/><br/>Abstract: The isotopic composition of the rainfall in northwestern Sicily (Italy, centralMediterranean) was investigated in the period February 2002 to March 2003. A rain gaugenetwork was installed and sampled monthly. The monthly values of the D and 18O ratiosshowed a wide range that reflected seasonal climatic variations. Mean weightedvalues were used to define an isotopic model of precipitation. Temporal variations indeuterium excess were also investigated. Using mean volume weighted values, the LocalMeteoric Water Line (LMWL) can be represented by the equation: dD = 4.7d18O 8.2(r2 = 0.96). Deuterium excess (d = dD 8d18O) was found to be strongly related toorography. The coastline samples were characterized by mean weighted deuterium excessvalues close to 12.5%; samples from inland areas showed values of 16%, while samplestaken from the main reliefs showed values close to 19%. In inland areas, isotopicexchange between raindrops and moisture could shift the deuterium excess values slightly.On the higher reliefs, the interaction between falling raindrops and orographic cloudscould shift the deuterium excess values significantly. The low slope of the LMWL couldbe referred to the high deuterium excess values of the higher sites and is related toorographic precipitation rather than to evaporation processes during the fall of theraindrops. The results obtained suggest that local orographic features may significantlychange the isotopic composition of precipitation. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2122/2387 Titolo: The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations<br/><br/>Autori: Aiuppa, A.; Dipartimento CFTA, Universit `a di Palermo, Palermo, Italy; Franco, A.; Dipartimento CFTA, Universit `a di Palermo, Palermo, Italy; von Glasow, R.; Institut f ¨ ur Umweltphysik, University of Heidelberg, Germany; Allen, A. G.; School of Geography, Earth and Environmental Sciences, University of Birmingham, UK; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Mather, T. A.; Earth Science Department, University of Oxford, UK; Pyle, D. M.; Earth Science Department, University of Oxford, UK; Valenza, M.; Dipartimento CFTA, Universit `a di Palermo, Palermo, Italy<br/><br/>Abstract: Improving the constraints on the atmospheric fate and depletion rates of acidic compoundspersistently emitted by non-erupting (quiescent) volcanoes is important forquantitatively predicting the environmental impact of volcanic gas plumes. Here, wepresent new experimental data coupled with modelling studies to investigate the chemicalprocessing of acidic volcanogenic species during tropospheric dispersion. Diffusivetube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcanoin eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in theAeolian Islands (northern Sicily). Sulphur dioxide (SO2), hydrogen sulphide (H2S),hydrogen chloride (HCl) and hydrogen fluoride (HF) concentrations in the volcanicplumes (typically several minutes to a few hours old) were repeatedly determined atdistances from the summit vents ranging from 0.1 to 10 km, and under different environmentalconditions. At both volcanoes, acidic gas concentrations were found todecrease exponentially with distance from the summit vents (e.g., SO2 decreases from 10 000 μg/m3 at 0.1 km from Etna’s vents down to 7 μg/m3 at 10 km distance),reflecting the atmospheric dilution of the plume within the acid gas-free backgroundtroposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showedno systematic changes with plume aging, and fit source compositions within analyticalerror. Assuming that SO2 losses by reaction are small during short-range atmospherictransport within quiescent (ash-free) volcanic plumes, our observations suggest that,for these short transport distances, atmospheric reactions for H2S and halogens arealso negligible. The one-dimensional model MISTRA was used to simulate quantitativelythe evolution of halogen and sulphur compounds in the plume of Mt. Etna. Modelpredictions support the hypothesis of minor HCl chemical processing during plumetransport, at least in cloud-free conditions. Larger variations in the modelled SO2/HClratios were predicted under cloudy conditions, due to heterogeneous chlorine cyclingin the aerosol phase. The modelled evolution of the SO2/H2S ratios is found to besubstantially dependent on whether or not the interactions of H2S with halogens areincluded in the model. In the former case, H2S is assumed to be oxidized in the atmospheremainly by OH, which results in minor chemical loss for H2S during plumeaging and produces a fair match between modelled and measured SO2/H2S ratios. Inthe latter case, fast oxidation of H2S by Cl leads to H2S chemical lifetimes in the earlyplume of a few seconds, and thus SO2 to H2S ratios that increase sharply during plumetransport. This disagreement between modelled and observed plume compositionssuggests that more in-detail kinetic investigations are required for a proper evaluationof H2S chemical processing in volcanic plumes. Sun, 01 Jan 2006 00:00:00 GMT