http://hdl.handle.net/2122/173 Thu, 23 May 2013 16:20:48 GMT 2013-05-23T16:20:48Z http://hdl.handle.net/2122/8232 Title: Dynamical budgets of the Antarctic Circumpolar Current using ocean general-circulation models Authors: Grezio, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Wells, N. C.; Southampton Oceanography Centre, UK; Ivchenko, V. O.; Southampton Oceanography Centre, UK; De Cuevas, B. A.; Southampton Oceanography Centre, UK Abstract: Three general-circulation models (FRAM, OCCAM and POP) are used to investigate the dynamics of the Antarctic Circumpolar Current (ACC) at the latitudes of the Drake Passage where the ACC is unbounded. In these general circulation models, bottom form stress balances the wind stress in the momentum budgets. In the vorticity budgets, the main balance is between wind curl and bottom pressure torque in FRAM, OCCAM and POP. Moreover, in the ACC belt all topographic features are regions of nonlinearity and bottom pressure torque variations, with the Drake Passage playing the largest role. Transient eddy Reynolds stresses (TERSs) play a different role in the three models. In the upper levels, TERSs accelerate the flow in the POP and FRAM models, but decelerate the flow in OCCAM. The behaviour of TERSs change throughout the whole water column in the ACC belt and Reynolds stresses have a dragging effect on the flow below the levels where the topography starts to obstruct the flow. The total volume transport in three models is very different. Additionally, the different spatial resolution, which results in a different level of eddy kinetic energy, has a significant influence on the transport. Fri, 31 Dec 2004 23:00:00 GMT http://hdl.handle.net/2122/8232 2004-12-31T23:00:00Z http://hdl.handle.net/2122/7104 Title: Societal need for improved understanding of climate change, anthropogenic impacts, and geo-hazard warning drive development of ocean observatories in European Seas Authors: Ruhl, H. A.; NOCS; Andrè, M.; UPC; Beranzoli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Çagatay, M. N.; ITU; Colaço, A.; Univ. Azores; Cannat, M.; IPGP; Dañobeitia, J. J.; CSIC-UTM; Favali, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Géli, L.; IFREMER; Gillooly, M.; IMI; Greinert, J.; NIOZ; Hall, P. O. J.; Univ. Goteborg; Huber, R.; MARUM; Karstensen, J.; Univ. Kiel; Lampitt, R. S.; NOCS; Larkin, K. E.; NOCS; Lykousis, V.; HCMR; Mienert, J.; Univ. Tromsø; Miranda, J. M.; Univ. Lisboa; Person, R.; IFREMER; Priede, I. G.; Univ. Aberdeen; Puillat, I.; IFREMER; Thomsen, L.; Jacobs Univ. Bremen; Waldmann, C.; MARUM Abstract: Society’s needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate. Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related? The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised. Fri, 31 Dec 2010 23:00:00 GMT http://hdl.handle.net/2122/7104 2010-12-31T23:00:00Z http://hdl.handle.net/2122/6920 Title: Quality Assessment of a 1985-2007 Mediterranean Sea re-analysis Authors: Adani, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Dobricic, S.; CMCC; Pinardi, N.; UNIBO Abstract: A simulation and two re-analyses from 1985 to 2007 have been produced for the Mediterranean Sea using different assimilation schemes: a Reduced Order Optimal Interpolation (SOFA) and a three-dimensional variational scheme (OceanVar). The observational data set consists of vertical temperature and salinity in-situ profiles and along-track satellite sea-level anomalies; daily mean fields of satellite sea surface temperature are used for correcting the air-sea fluxes. This paper assesses the quality of the re-analyses with respect to observations and the simulation. Both the SOFA and OceanVar schemes give very similar root mean square errors and biases for temperature and salinity fields compared with the assimilated observations. The largest errors are at the thermocline level and in regions of large eddy field variability. However, OceanVar gives 20% better results for sea-level anomaly root mean square error. Tue, 30 Nov 2010 23:00:00 GMT http://hdl.handle.net/2122/6920 2010-11-30T23:00:00Z http://hdl.handle.net/2122/5979 Title: Effects of increased CO2 levels on monsoons Authors: Cherchi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Alessandri, A.; Centro Euromediterraneo per i Cambiamenti Climatici, Bologna, Italy; Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Navarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Abstract: Increased atmospheric carbon dioxide concentration provided warmer atmospheric temperature and higher atmospheric water vapor content, but not necessarily more precipitation. A set of experiments performed with a state-of-the-art coupled general circulation model forced with increased atmospheric CO2 concentration (2, 4 and 16 times the present-day mean value) were analyzed and compared with a control experiment to evaluate the effect of increased CO2 levels on monsoons. Generally, the monsoon precipitation responses to CO2 forcing are largest if extreme concentrations of carbon dioxide are used, but they are not necessarly proportional to the forcing applied. In fact, despite a common response in terms of an atmospheric water vapor increase to the atmospheric warming, two out of the six monsoons studied simulate less or equal summer mean precipitation in the 16xCO2 experiment compared to the intermediate sensitivity experiments. The precipitation differences between CO2 sensitivity experiments and CTRL have been investigated specifying the contribution of thermodynamic and purely dynamic processes. As a general rule, the differences depending on the atmospheric moisture content changes (thermodynamic component) are large and positive, and they tend to be damped by the dynamic component associated with the changes in the vertical velocity. However, differences are observed among monsoons in terms of the role played by other terms (like moisture advection and evaporation) in shaping the precipitation changes in warmer climates. The precipitation increase, even if weak, occurs despite a weakening of the mean circulation in the monsoon regions(‘‘precipitation-wind paradox’’). In particular, the tropical east-west Walker circulation is reduced, as found from velocity potential analysis. The meridional component of the monsoon circulation is changed as well, with larger (smaller) meridional (vertical) scales. Sat, 03 Apr 2010 22:00:00 GMT http://hdl.handle.net/2122/5979 2010-04-03T22:00:00Z http://hdl.handle.net/2122/5292 Title: New geological insights and structural control on fluid circulation in La Fossa cone (Vulcano, Aeolian Islands, Italy) Authors: Barde-Cabusson, S.; Dipartimento di Scienze della Terra, Università Degli Studi di Firenze, Italy; LMV, Université Blaise Pascal, Clermont-Ferrand, France; Finizola, A.; Laboratoire GéoSciences Réunion, UR, IPGP, UMR 7154, Saint-Denis, La Réunion, France; Istituto Nazionale di Geofisica e Vulcanologia, Palermo, Italy; Revil, A.; Colorado School of Mines, Dept. of Geophysics, Golden, CO, USA; CNRS-LGIT (UMR 5559), University of Savoie, Equipe Volcan, Chambéry, France; Ricci, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Piscitelli, S.; IMAA-CNR, Laboratory of Geophysics Tito Scalo (PZ), Italy; Rizzo, E.; IMAA-CNR, Laboratory of Geophysics Tito Scalo (PZ), Italy; Angeletti, B.; CNRS-CEREGE, Université Paul Cézanne, Aix en Provence, France; Balasco, M.; IMAA-CNR, Laboratory of Geophysics Tito Scalo (PZ), Italy; Bennati, L.; Dept. of Earth & Atmospheric Sciences, Purdue University, West Lafayette, USA; Byrdina, S.; LMV, Université Blaise Pascal, Clermont-Ferrand, France; Equipe de Géomagnétisme, IPGP, UMR 7154, 4, Place Jussieu, 75005 Paris, France; Carzaniga, N.; Dipartimento di Scienze della Terra, Università Degli Studi di Firenze, Italy; Crespy, A.; CNRS-CEREGE, Université Paul Cézanne, Aix en Provence, France; Di Gangi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Morin, J.; Laboratoire GéoSciences Réunion, UR, IPGP, UMR 7154, Saint-Denis, La Réunion, France; Université Paris 1, Panthéon-Sorbonne, Paris, France; Perrone, A.; IMAA-CNR, Laboratory of Geophysics Tito Scalo (PZ), Italy; Rossi, M.; Dipartimento di Geoscienze, Università di Padova, Italy; Università Milano-Bicocca, Milan, Italy; Roulleau, E.; GEOTOP-UQAM-McGill, Montréal, Canada; Suski, B.; Université de Lausanne (UNIL), Institut de Géophysique, Lausanne, Switzerland; CNRS-CEREGE, Université Paul Cézanne, Aix en Provence, France; Villeneuve, N.; Institut de Recherche pour le Développement, US 140 ESPACE, La Réunion, France Abstract: Electric resistivity tomography (ERT), self-potential (SP), soil CO2 flux, and temperature are used to study the inner structure of La Fossa cone (Vulcano, Aeolian Islands). Nine profiles were performed across the cone with a measurement spacing of 20 m. The crater rims of La Fossa cone are underlined by sharp horizontal resistivity contrasts. SP, CO2 flux, and temperature anomalies underline these boundaries which we interpret as structural limits associated to preferential circulation of fluids. The Pietre Cotte crater and Gran Cratere crater enclose the main hydrothermal system, identified at the centre of the edifice on the base of low electrical resistivity values (b20 Ω m) and strong CO2 degassing, SP, and temperature anomalies. In the periphery, the hydrothermal activity is also visible along structural boundaries such as the Punte Nere, Forgia Vecchia, and Palizzi crater rims and at the base of the cone, on the southern side of the edifice, along a fault attributed to the NW main tectonic trend of the island. Inside the Punte Nere crater, the ERT sections show an electrical resistive body that we interpret as an intrusion or a dome. This magmatic body is reconstructed in 3D using the available ERT profiles. Its shape and position, with respect to the Pietre Cotte crater fault, allows replacing this structure in the chronology of the development of the volcano. It corresponds to a late phase of activity of the Punte Nere edifice. Considering the position of the SP, soil CO2 flux, and temperature maxima and the repartition of conductive zones related to hydrothermal circulation with respect to the main structural features, La Fossa cone could be considered as a relevant example of the strong influence of preexisting structures on hydrothermal fluid circulation at the scale of a volcanic edifice. Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2122/5292 2008-12-31T23:00:00Z http://hdl.handle.net/2122/2550 Title: On the relationship between the water mass pathways and mesoscale variability in the Western Mediterranean Sea Authors: Demirov, E. K.; Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John’s, NL, Canada; Pinardi, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Abstract: The role of mesoscales on the formation and spreading of water masses in the Western Mediterranean Sea (WMED) is studied with an ocean general circulation model. It is found that the model reproduces the major features of the observed mesoscale variability during the preconditioning of the deep convection in the Gulf of Lions, mixing and spreading of deep and intermediate waters and also the large mesoscale eddiess evolution in the Algerian Basin. The instability of the transition zone between old and newly formed deep waters, which takes place after the violent mixing stages of the deep convection, leads to collapse of the mixed patch and formation of mesoscale eddies. Some of these eddies propagate out of the Gulf of Lions transporting deep waters into the Algerian Basin. The rest of the mesoscale eddies filled with newly formed deep waters remain in the Gulf of Lions, and tend to merge, enlarge and reorganize in an area with two or three large cyclonic eddies. After the cyclonic eddies reach the Algerian Basin they interact with the intense mesoscale field existing there. The model data together with the available satellite SLA data reveal a regular westward propagation of mesoscale eddies in the Northern Algerian Basin. This transport together with southward propagation of mesoscale eddies out of the Gulf of Lions is suggesting that the intermediate and deep waters of the WMED are transported westward by mesoscale eddies. Equivalently we can argue the intermediate and deep waters conveyor belt of the WMED is eddy driven. Sat, 31 Dec 2005 23:00:00 GMT http://hdl.handle.net/2122/2550 2005-12-31T23:00:00Z http://hdl.handle.net/2122/1177 Title: A generalized model of pelagic biogeochemistry for the global ocean ecosystem. Part II: numerical simulations. Authors: Vichi, M.; 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 Abstract: This paper presents a global ocean implementation of a multi-component model of marine pelagic biogeochemistry coupled on-line with an ocean general circulation model forced with climatological surface fields (PELAgic biogeochemistry for Global Ocean Simulations, PELAGOS). The final objective is the inclusion of this model as a component in an Earth System model for climate studies. The pelagic model is based on a functional stoichiometric representation of marine biogeochemical cycles and allows simulating the dynamics of C, N, P, Si, O and Fe taking into account the variation of their elemental ratios in the functional groups. The model also includes a parameterization of variable chlorophyll:carbon ratio in phytoplankton, carrying chl as a prognostic variable. The first part of the paper analyzes the contribution of non-local advective-diffusive terms and local vertical processes to the simulated chl distributions. The comparison of the three experiments shows that the mean chl distribution at higher latitudes is largely determined by mixing processes, while vertical advection dominates the distribution in the equatorial upwelling regions. Horizontal advective and diffusive processes are necessary mechanisms for the shape of chl distribution in the sub-tropical Pacific. In the second part, the results have been compared with existing datasets of satellite-derived chlorophyll, surface nutrients, estimates of phytoplankton community composition and primary production data. The agreement is reasonable both in terms of the spatial distribution of annual means and seasonal variability in different dynamical oceanographic regions. Results indicate that some of the model biases in chl and surface nutrients distributions can be related to deficiencies in the simulation of physical processes such as advection and mixing. Other discrepancies are attributed to inadequate parameterizations of phytoplankton functional groups. The model has skill in reproducing the overall distribution of large and small phytoplankton but tends to underestimate diatoms in the northern higher latitudes and overestimate nanophytoplankton with respect to picoautotrophs in oligotrophic regions. The performance of the model is discussed in the context of its use in climate studies and an approach for improving the parameterization of functional groups in deterministic models is outlined. Mon, 19 Jun 2006 09:41:34 GMT http://hdl.handle.net/2122/1177 2006-06-19T09:41:34Z http://hdl.handle.net/2122/981 Title: Tropical Pacific influences on the North Atlantic Thermohaline Circulation Authors: Latif, M.; Max-Planck-Institut für Meteorologie, Hamburg, Germany Abstract: Most global climate models simulate a weakening of the North Atlantic Thermohaline Circulation (THC) in response to enhanced greenhouse warming. Both surface warming and freshening in high latitudes, the so-called sinking region, contribute to the weakening of the THC. Some models simulate even a complete breakdown of the THC at sufficiently strong forcing. Here results from a state-of-the-art global climate model are presented that does not simulate a weakening of the THC in response to greenhouse warming. Large-scale air-sea interactions in the tropics, similar to those operating during present-day El Niños, lead to anomalously high salinities in the tropical Atlantic. These are advected into the sinking region, thereby increasing the surface density and compensating the effects of the local warming and freshening. The results of the model study are corroborated by the analysis of observations. Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/2122/981 2002-12-31T23:00:00Z http://hdl.handle.net/2122/980 Title: Variability of Atlantic Ocean heat transport and its effects on the atmosphere Authors: Dong, B.; Centre for Global Atmospheric Modelling, Department of Meteorology,University of Reading, U.K.; Sutton, R. T.; Centre for Global Atmospheric Modelling, Department of Meteorology,University of Reading, U.K. Abstract: The variability of the Atlantic meridional Ocean Heat Transport (OHT) has been diagnosed from a simulation of a coupled ocean-atmosphere general circulation model, and the mechanisms responsible for this variability have been elucidated. It has been demonstrated that the interannual variability in Atlantic OHT is dominated by windstress-driven Ekman fluctuations. In contrast, the decadal and multidecadal variability is associated with the fluctuations of the Thermohaline Circulation (THC), driven by the fluctuations in deep convection over the Greenland-Iceland-Norwegian (GIN) Sea. The fluctuations of OHT induce Ocean Heat Content (OHC), and Sea Surface Temperature (SST) anomalies over the tropical and subtropical North Atlantic. The SST anomalies, in turn, have an impact on the atmosphere. The lead-lag relationships between the fluctuations of THC-related OHT and those of OHC and SST raise the possibility that a knowledge of OHT fluctuations could be used to predict variations in Atlantic Sea surface temperatures, and perhaps aspects of climate, several years in advance. A comparison of results from a second, independent, coupled model simulation is also presented, and similar conclusions reached. Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/2122/980 2002-12-31T23:00:00Z http://hdl.handle.net/2122/416 Title: Geochemical processes governing the chemistry of groundwater hosted within the Hyblean aquifers Authors: Grassa, F.; PhD Thesis Abstract: A raingauge network made of six stations was installed in the Hyblean region. Stations were located at different altitudes (from 5 m to 986 m a.s.l.) and along two directions (E-W and SW-NE). Rainwater samples were monthly collected for stable isotope measurements. Spatial distribution of rainwater isotope composition has confirmed the wet air masses move from South-East/South-West toward North. Water balance has highlighted that the annual volume of infiltrating waters is in the range of 1-1.5 *105 m3 Km-2. 82 well waters and 12 spring waters located within the Hyblean Plateau (South-Estern Sicily), were also collected from 1999 to 2001 during several surveys for chemical (major,minor and trace elements) analyses. Water chemistry allowed to identify two main aquifers: the first aquifer hosted within sedimentary rocks is characterized by earthalkaline bicarbonate waters, while the second aquifer, located within the volcanic deposits (mainly towards North- North-East) is characterized by groundwaters evolving from earthalkaline bicarbonate water-type towards a Na-HCO3-type. A slightly anomaly in water temperature (24-28°C) have been identified along the northern margin, while the lower Eh values have been recorded along the M.Lauro-Scicli and the Hyblean Malta Escarpment fault systems. Isotope composition of groundwaters has suggested the occurrence of evaporative processes during soil infiltration having a dD/d18O slope close to 4.5. Chemical and isotope composition of dissolved gases (d13CTDIC, d13CCH4, 3He/4He) have revealed, as expected, that deeply-derived gases rise along the main tectonic discontinuities. Chemical and isotope analyses of dissolved carbon have revealed the existence of two sampling sites (NA and FE samples) attesting the interaction between groundwaters and a consistent amount of deep inorganic carbon dioxide. He isotope ratios (from 0.81Ra to 6.19 Ra) have revealed the occurrence of mixing process, in different proportions, between crustal and mantle components. On the base of the obtained results, a clear picture of the groundwaters circulation within the Hyblean aquifers has been drawn. In framework of projecting of a geochemical network for the continuous monitoring of the local seismic activity the most suitable geochemical parameters and the sites of great interest have been identified. Mon, 31 Dec 2001 23:00:00 GMT http://hdl.handle.net/2122/416 2001-12-31T23:00:00Z