http://hdl.handle.net/2122/145 Wed, 22 May 2013 17:40:56 GMT 2013-05-22T17:40:56Z http://hdl.handle.net/2122/8291 Title: Water and dissolved gas geochemistry of the monomictic Paterno sinkhole (central Italy) Authors: Tassi, F.; University of Florence; Cabassi, J.; University of Florence; Rouwet, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Palozzi, R.; Università Tuscia; Marcelli, M.; Università Roma La Sapienza; Quartararo, M.; Roma Tor Vergata; Capecchiacci, F.; University of Florence; Vaselli, O.; University of Florence Abstract: This paper describes the chemical and isotope features of water and dissolved gases from lake Paterno (max. depth 54 m), a sinkhole located in the NE sector of the S. Vittorino plain (Rieti, Central Italy), where evidences of past and present hydrothermal activity exists. In winter (February 2011) lake Paterno waters were almost completely mixed, whereas in summer time (July 2011) thermal and chemical stratifications established. During the stratification period, water and dissolved gas chemistry along the vertical water column were mainly controlled by biological processes, such as methanogenesis, sulfate-reduction, calcite precipitation, denitrification, and NH4 and H2 production. Reducing conditions at the interface between the bottom sediments and the anoxic waters are responsible for the relatively high concentrations of dissolved iron (Fe) and manganese (Mn), likely present in their reduced oxidation state. Minerogenic and biogenic products were recognized at the lake bottom even during the winter sampling. At relatively shallow depth the distribution of CH4 and CO2 was controlled by methanotrophic bacteria and photosynthesis, respectively. The carbon isotope signature of CO2 indicates a significant contribution of deep-originated inorganic CO2 that is related to the hydrothermal system feeding the CO2-rich mineralized springs discharging in the surrounding areas of lake Paterno. The seasonal lake stratification likely controls the vertical and horizontal distribution of fish populations in the different periods of the year. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8291 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8168 Title: Process studies on the ecological coupling between sea ice algae and phytoplankton Authors: Tedesco, L.; Marine Research Centre, Finnish Environment Institute; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Thomas, D.; Marine Research Centre, Finnish Environment Institute Abstract: The seasonal dynamics of pelagic and sea ice communities are closely related in ice-covered waters, however, modelling works that analyse such interactions are scarce. We use the Biogeochemical Flux Model in Sea Ice (BFM-SI) coupled to the pelagic Biogeochemical Flux Model (BFM) in a study area in Greenland to quantitatively investigate: (1) the significance of photoacclimation/photoadaptation strategies of autotrophs, (2) the fate of the sea ice biomass in case of algae seeding, algae aggregation and at different mixed layer depths and (3) the changes in community production under a climate change scenario. The results show that sea ice algae need to be both photoacclimated and photoadapted to the sea ice environment in order to grow, while phytoplankton may adopt different strategies for optimising their growth. The seeding of the phytoplankton bloom shows to be driven, both in timing and magnitude, by the viability of sea ice algae and by the degree of aggregation of algae released from the ice, which also affects the sinking rate to the sea floor. Under a mild climate change scenario (SRES B2, 2071–2090) the sea ice community is projected to be generally more productive, whereas phytoplankton growth will be reduced because the melt of sea ice will occur earlier in the season when light is less favourable to sustain the growth. While it is generally anticipated that the melting of multi-year ice in the Arctic Ocean will cause an increase in marine production, this study shows that seasonal ice-covered seas in the Northern hemisphere may actually be less productive and may shift to more oligotrophic conditions within the next 100 years. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8168 2011-12-31T23:00:00Z http://hdl.handle.net/2122/5743 Title: An enhanced sea-ice thermodynamic model applied to the Baltic sea Authors: Tedesco, L.; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Haapala, J.; Finnish Institute of Marine Research; Stipa, T.; Finnish Institute of Marine Research Abstract: A refined Semtner 0-layer sea-ice model (ESIM1) is presented and applied to the Baltic landfast sea-ice. The physical model is capable of simulating seasonal changes of snow and ice thickness. Particular attention is paid to reproducing the snow-ice and the super-imposed-ice formation which play important roles in the total mass balance of the Baltic sea-ice. The model prognostic variables include all kinds of ice and snow layers that may be present during a Baltic landfast ice season and, in general, in every coastal area of an ice-covered ocean. The assessment of the model capabilities was done for 1979–1993 for four different stations in the Baltic Sea. A sensitivity test stresses the relevant role of some of the physical parameters, such as the oceanic heat flux, while a scenario analysis highlights the robustness of the model to perturbed physical forcing. Our results show that one of the key variables in modelling sea-ice thermodynamics is the snow layer and its metamorphism, and including the meteoric ice dynamics into a sea ice model is relevant to properly simulate any ice season, also in view of climate change scenarios Thu, 26 Feb 2009 23:00:00 GMT http://hdl.handle.net/2122/5743 2009-02-26T23:00:00Z http://hdl.handle.net/2122/4529 Title: An enhanced sea-ice thermodynamic model applied to the Baltic Sea Authors: Tedesco, L.; Centro Euro Mediterraneo per i Cambiamenti Climatici; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Haapala, J.; Finnish Institute of Marine Research; Stipa, T.; Finnish Institute of Marine Research Abstract: A refined Semtner 0-layer sea-ice model (ESIM1) is presented and applied to the Baltic landfast sea-ice. The physical model is capable of simulating seasonal changes of snow and ice thickness. Particular attention is paid to reproducing the snow-ice and the super-imposed-ice formation which play important roles in the total mass balance of the Baltic sea-ice. The model prognostic variables include all kinds of ice and snow layers that may be present during a Baltic landfast ice season and, in general, in every coastal area of an ice-covered ocean. The assessment of the model capabilities was done for 1979–1993 for four different stations in the Baltic Sea. A sensitivity test stresses the relevant role of some of the physical parameters, such as the oceanic heat flux, while a scenario analysis highlights the robustness of the model to perturbed physical forcing. Our results show that one of the key variables in modelling sea-ice thermodynamics is the snow layer and its metamorphism, and including the meteoric ice dynamics into a sea ice model is relevant to properly simulate any ice season, also in view of climate change scenarios Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2122/4529 2007-12-31T23:00:00Z http://hdl.handle.net/2122/3394 Title: Introduction to ‘Antarctic cryosphere and Southern Ocean climate evolution (Cenozoic-Holocene)’ Authors: Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Nelson, A. E.; British Antarctic Survey, High Cross, Madingley Road, CB3 0ET, Cambridge, UK; Haywood, A. M.; School of Earth and Environment, University of Leeds, LS2 9JT, UK Abstract: The Antarctic region has profoundly affected the global climates of the Cenozoic, influencing sea levels, atmospheric composition and dynamics, and ocean circulation. According to IPCC-2007 (IPCC, 2007) worst-case scenario projections, temperatures by 2100 are likely to exceed those that have been experienced by the Earth in the last 40 myr when the Antarctic Ice Sheet may have first developed. This implies that the Ice Sheet will become unsustainable, with huge implications for global sea-levels. Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/2122/3394 2006-12-31T23:00:00Z