http://hdl.handle.net/2122/124 2013-05-21T07:48:43Z http://hdl.handle.net/2122/8576 Title: A synthesis of the Antarctic surface mass balance during the last 800 yr Authors: Frezzotti, M.; ENEA, Agenzia Nazionale per le nuove tecnologie, l’energia e lo sviluppo sostenibile, Rome, Italy; Scarchilli, C.; ENEA, Agenzia Nazionale per le nuove tecnologie, l’energia e lo sviluppo sostenibile, Rome, Italy; Becagli, S.; Department of Chemistry, University of Florence, Sesto F.no, Italy; Proposito, M.; ENEA, Agenzia Nazionale per le nuove tecnologie, l’energia e lo sviluppo sostenibile, Rome, Italy; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Global climate models suggest that Antarctic snowfall should increase in a warming climate and mitigate rises in the sea level. Several processes affect surface mass balance (SMB), introducing large uncertainties in past, present and future ice sheet mass balance. To provide an extended perspective on the past SMB of Antarctica, we used 67 firn/ice core records to reconstruct the temporal variability in the SMB over the past 800 yr and, in greater detail, over the last 200 yr. Our SMB reconstructions indicate that the SMB changes over most of Antarctica are statistically negligible and that the current SMB is not exceptionally high compared to the last 800 yr. High-accumulation periods have occurred in the past, specifically during the 1370s and 1610s. However, a clear increase in accumulation of more than 10% has occurred in high SMB coastal regions and over the highest part of the East Antarctic ice divide since the 1960s. To explain the differences in behaviour between the coastal/ice divide sites and the rest of Antarctica, we suggest that a higher frequency of blocking anticyclones increases the precipitation at coastal sites, leading to the advection of moist air in the highest areas, whereas blowing snow and/or erosion have significant negative impacts on the SMB at windy sites. Eight hundred years of stacked records of the SMB mimic the total solar irradiance during the 13th and 18th centuries. The link between those two variables is probably indirect and linked to a teleconnection in atmospheric circulation that forces complex feedback between the tropical Pacific and Antarctica via the generation and propagation of a large-scale atmospheric wave train. 2013-02-19T23:00:00Z http://hdl.handle.net/2122/8498 Title: Extent of low-accumulation ‘wind glaze’ areas on the East Antarctic plateau: implications for continental ice mass balance Authors: Scambos, T. A.; National Snow and Ice Data Center, University of Colorado, Boulder, Boulder, CO, USA; Frezzotti, M.; ENEA-CRE, Casaccia, Rome, Italy; Haran, T.; National Snow and Ice Data Center, University of Colorado, Boulder, Boulder, CO, USA; Bohlander, J.; National Snow and Ice Data Center, University of Colorado, Boulder, Boulder, CO, USA; Lenaerts, J. T. M.; Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands; Van Den Broeke, M. R.; Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands; Jezek, K.; Byrd Polar Research Center, The Ohio State University, Columbus, OH, USA; Long, D.; Department of Electrical Engineering, Brigham Young University, Provo, UT, USA; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Farness, K.; Byrd Polar Research Center, The Ohio State University, Columbus, OH, USA; Neumann, T.; NASA Goddard Space Flight Center, Greenbelt, MD, USA; Albert, M.; Thayer School of Engineering, Dartmouth College, Hanover, NH, USA; Winther, J.-G.; Norwegian Polar Institute, Tromsø, Norway Abstract: Persistent katabatic winds form widely distributed localized areas of near-zero net surface accumulation on the East Antarctic ice sheet (EAIS) plateau. These areas have been called ‘glaze’ surfaces due to their polished appearance. They are typically 2–200km2 in area and are found on leeward slopes of ice-sheet undulations and megadunes. Adjacent, leeward high-accumulation regions (isolated dunes) are generally smaller and do not compensate for the local low in surface mass balance (SMB). We use a combination of satellite remote sensing and field-gathered datasets to map the extent of wind glaze in the EAIS above 1500m elevation. Mapping criteria are derived from distinctive surface and subsurface characteristics of glaze areas resulting from many years of intense annual temperature cycling without significant burial. Our results show that 11.2 1.7%, or 950 143 103 km2, of the EAIS above 1500m is wind glaze. Studies of SMB interpolate values across glaze regions, leading to overestimates of net mass input. Using our derived wind-glaze extent, we estimate this excess in three recent models of Antarctic SMB at 46–82 Gt. The lowest-input model appears to best match the mean in regions of extensive wind glaze. 2012-07-31T22:00:00Z http://hdl.handle.net/2122/7742 Title: The sensitivity of the Late Saalian (140 ka) and LGM (21 ka) Eurasian ice sheets to sea surface conditions Authors: Colleoni, F.; Centro Euro-Mediterraneo per i Cambiamenti Climatici; Liakka, J.; Department of Meteorology, Stockholm University; Krinner, G.; Laboratoire de Glaciologie et Ge´ophysique de l’Environnement, UJF, CNRS; Jakobsson, M.; Department of Geological Sciences, Stockholm University; Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Peyaud, V.; Laboratoire de Glaciologie et Ge´ophysique de l’Environnement, UJF, CNRS Abstract: This work focuses on the Late Saalian (140 ka) Eurasian ice sheets’ surface mass balance (SMB) sensitivity to changes in sea surface temperatures (SST). An Atmospheric General Circulation Model (AGCM), forced with two preexisting Last Glacial Maximum (LGM, 21 ka) SST reconstructions, is used to compute climate at 140 and 21 ka (reference glaciation). Contrary to the LGM, the ablation almost stopped at 140 ka due to the climatic cooling effect from the large ice sheet topography. Late Saalian SST are simulated using an AGCM coupled with a mixed layer ocean. Compared to the LGM, these 140 ka SST show an inter-hemispheric asymmetry caused by the larger ice-albedo feedback, cooling climate. The resulting Late Saalian ice sheet SMB is smaller due to the extensive simulated sea ice reducing the precipitation. In conclusion, SST are important for the stability and growth of the Late Saalian Eurasian ice sheet. 2010-12-31T23:00:00Z http://hdl.handle.net/2122/4066 Title: Snow dunes and glazed surfaces in Antarctica: new field and remote-sensing data Authors: Frezzotti, M.; ENEA, Centro Ricerche Casaccia, P.O. Box 2400, I-00100 Rome, Italy; Gandolfi, S.; DISTART, Università di Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy; La Marca, F.; Dipartimento di ICMMPM, Università di Roma "La Sapienza", Via Eudossiana 18, I-00184 Rome, Italy; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: As part of the International Trans-Antarctic Scientific Expedition project, the Italian Antarctic Programme undertook two traverses from the Terra Nova station to Talos Dome and to Dome C. Along the traverses, the party carried out several tasks (drilling, glaciological and geophysical exploration). The difference in spectral response between glazed surfaces and snow makes it simple to identify these areas on visible/near-infrared satellite images. Integration of field observation and remotely sensed data allows the description of different mega-morphologic features: wide glazed surfaces, sastrugy glazed surface fields, transverse dunes and megadunes. Topography global positioning system, ground penetrating radar and detailed snow-surface surveys have been carried out, providing new information about the formation and evolution of mega-morphologic features. The extensive presence, (up to 30%) of glazed surface caused by a long hiatus in accumulation, with an accumulation rate of nil or slightly negative, has a significant impact on the surface mass balance of a wide area of the interior part of East Antarctica. The aeolian processes creating these features have important implications for the selection of optimum sites for ice coring, because orographic variations of even a few metres per kilometre have a significant impact on the snow-accumulation process. Remote-sensing surveys of aeolian macro-morphology provide a proven, high-quality method for detailed mapping of the interior of the ice sheet's prevalent wind direction and could provide a relative indication of wind intensity. 2001-12-31T23:00:00Z http://hdl.handle.net/2122/4065 Title: A New Bedrock Map of the Dome C Area Authors: Forieri, A.; Università degli Studi di Milano, Sezione Geofisica, via Cicognara 7, 1-20129 Milano - Italy and Dipartimento di Scienze della Terra, Università di Siena, Via del Laterino 8, 53100 Siena - Italy; Tabacco, I. E.; Università degli Studi di Milano, Sezione Geofisica, via Cicognara 7, 1-20129 Milano - Italy; Della Vedova, A.; Università degli Studi di Milano, Sezione Geofisica, via Cicognara 7, 1-20129 Milano - Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Passerini, A.; Università degli Studi di Milano Bicocca, Piazza della Scienza 1, 1-20126 Milano - Italy Editors: Frezzotti, M.; ENEA Progetto Clima, PO Box 2400, 000100 Roma AD - Italy; Maggi, V.; Department of Environmental Sciences, University of Milano–Bicocca, Piazza della Scienza 1, I-20126 Milan, Italy Abstract: A large number of airborne and ground-based radar echo sounding (RES) data were collected in the Dome C - Vostok region during the Italian Antarctic expeditions in 1995, 1997, 1999 and 2001. Tabacco et al. (1998) used the 1995 data to produce a topographic map of Dome C. We present a new map of bed topography based on all collected radar data. 2002-12-31T23:00:00Z http://hdl.handle.net/2122/4064 Title: Un karst sous la glace de l'Antarctide ? Authors: Bini, A.; Università degli Studi di Milano, Sez. Geologia, Via Mangiagalli 34, I-20133 Milan, Italy; Forieri, A.; Università degli Studi di Siena, Dip. Scienze della Terra, Via del Laterino 8, I-53100 Siena, Italy; Remy, F.; Laboratoire d’Etudes en Géophysique et Océanographie Spatiales, 18 av. Edouard Belin, 31055 Toulouse Cedex, France; Tabacco, I. E.; Università degli Studi di Milano, Sez. Geofisica, Via Cicognara 7, I-20129 Milan, Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccoli, L.; Università degli Studi di Milano, Sez. Geologia, Via Mangiagalli 34, I-20133 Milan, Italy Abstract: A new bedrock map of the Dome C area based on all radar data collected during Italian Antarctic Expeditions in 1995, 1997, 1999 and 2001 is presented. The map can clearly distinguish the Dome C plateau, along with some valleys and ridges develop. The plateau develops at three different altimetric levels and its morphology is characterized by hills and closed depressions. There are no visible features which can be ascribed to glacial erosion or deposition. The major valley is 15km wide and 500m deep; its axis is parallel to that of other valleys and ridges in the plateau. The valley bottom is not flat, but contains a saddle in its centre. The morphology of the major valley could be considered as a relict one which was not modified by the overlying ice cap. Two big ridges, characterized by hills, saddles and depressions, lie near the boundaries of the area. The hill and depression landscape may be the results of two different processes the weathering of granitic rocks, with the development of a "Wemi-oranges" and inselberg landscape, or the karstification of limestones, and development of a cone karst. The karstic hypothesis should be the more suitable, but it is impossible to exclude the granitic rock weathering. Both proposed genetic hypotheses call for a warm humide climate and a long period of stability in a continental environment. Consequently, the ice cap did not largely modified the landscape. 2002-12-31T23:00:00Z http://hdl.handle.net/2122/4063 Title: Evidence of 14 New Subglacial Lakes in the Dome C-Vostok Area Authors: Tabacco, I. E.; Università degli Studi di Milano, Sezione Geofisica, Via Cicognara 7, 20129 Milano - Italy; Forieri, A.; Università degli Studi di Milano, Sezione Geofisica, Via Cicognara 7, 20129 Milano - Italy and Dipartimento di Scienze della Terra, Università di Siena, Via del Laterino 8, 53100 Siena - Italy; Della Vedova, A.; Università degli Studi di Milano, Sezione Geofisica, Via Cicognara 7, 20129 Milano - Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Passerini, A.; Università degli Studi di Milano Bicocca, Piazza della Scienza 1 , 20126 Milano - Italy Editors: Frezzotti, M.; ENEA Progetto Clima, PO Box 2400, 000100 Roma AD - Italy; Maggi, V.; Department of Environmental Sciences, University of Milano–Bicocca, Piazza della Scienza 1, I-20126 Milan, Italy Abstract: In the last few years subglacial lakes have been of great interest to the scientific community for various reasons. The lakes could be an unknown extreme habitat, which have been isolated from the terrestrial biosphere for a long time. They may have formed before the ice sheet and could perhaps reveal environmental conditions prior to its formation. Lastly, they may play a role in the current dynamics of the ice sheet. Strong radar reflections from the base of the ice sheet can generally be ascribed to either water-saturated basal sediments or subglacial lakes (Oswald & Robin, 1973). Based on radar data alone, the identification of lakes is possible if other features are present: flat and quite horizontal reflectors with nearly constant echo intensity and sharp edges similar to the margins of a catchment basin (Siegert et al., 1996; Siegert & Ridley, 1998; German & Siegert, 1999; Siegert, 2000; Tabacco et al., 2002). Subglacial lakes can be expressed in the overlying ice sheet as extremely flat surfaces with respect to the surrounding slopes (Ridley et al., 1993; Kapitsa et &l996 ; Siegert & Ridley,1998; Tabacco et al., 2002). To date, about 70 lakes have been discovered in all of Antarctica (Siegert et al.,1996); 21 of these are located in the Dome C-Vostok region. 2002-12-31T23:00:00Z http://hdl.handle.net/2122/4062 Title: Reflecting Sub-Ice Surfaces Observed by Radio Echo Sounding System Authors: Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tabacco, I. E.; Università di Milano - Sezione Geofisica, Milano - Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Editors: Frezzotti, M.; ENEA Progetto Clima, PO Box 2400, 000100 Roma AD - Italy; Maggi, V.; Department of Environmental Sciences, University of Milano–Bicocca, Piazza della Scienza 1, I-20126 Milan, Italy Abstract: The reflection coefficient (R) at the interface of two media provides information on their electromagnetic nature. If the first medium is known, e.g. air (or ice, that in a broad interval of physical conditions maintains certain propagative characteristics nearly constant), the electromagnetic properties of the second medium can be determined. Hence, the ice/seawater, ice/water and ice/rock interfaces exhibit different reflection coefficients which can be detected by means of a RES system (Tabacco et al., 1999; Tabacco et al., 2000). The length of the radio wave does not allow the employment of sophisticated antennas, and so folded dipoles are arranged beneath the wings of the aircraft. As a consequence, the transmitted radio wave beam illuminates a relatively large area, and the power of the echo signal greatly depends on the shape of the reflecting surfaces. An electromagnetic analysis shows that, in certain conditions, the variations in amplitude detected by the system are mainly due to focusing or defocusing effects determined by the shape of the reflectors (Bianchi et al., 2001; Tabacco et al., 1999). 2002-12-31T23:00:00Z http://hdl.handle.net/2122/4052 Title: Spatial and temporal variability of snow accumulation in East Antarctica from traverse data Authors: Frezzotti, M.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Clima Globale’, Rome, Italy; Pourchet, M.; Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, Saint Martin d’Hères, France; Flora, O.; Dipartimento di Scienze Geologiche, Ambientali e Marine, University of Trieste, Trieste, Italy; Gandolfi, S.; Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, University of Bologna, Bologna, Italy; Gay, M.; Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, Saint Martin d’Hères, France; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Vincent, C.; Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, Saint Martin d’Hères, France; Becagli, S.; Dipartimento di Chimica, University of Florence, Florence, Italy; Gragnani, R.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Clima Globale’, Rome, Italy; Proposito, M.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Clima Globale’, Rome, Italy; Severi, M.; Dipartimento di Chimica, University of Florence, Florence, Italy; Traversi, R.; Dipartimento di Chimica, University of Florence, Florence, Italy; Udisti, R.; Dipartimento di Chimica, University of Florence, Florence, Italy; Fily, M.; Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, Saint Martin d’Hères, France Abstract: Recent snow accumulation rate is a key quantity for ice core and mass balance studies. Several accumulation measurement methods (stake farm, fin core, snow-radar profiling, surface morphology, remote sensing) were used, compared and integrated at eight sites along a transect from Terra Nova Bay to Dome C (East Antarctica) to provide information about the spatial and temporal variability of snow accumulation. Thirty-nine cores were dated by identifying tritium/β marker levels (1965–66[AUTHOR: Please check dates, I don’t think this agrees with table 1]) and no-sea-salt (nss) SO4 raised to the power of 2– spikes of the Tambora volcanic event (1816) in order to provide information on temporal variability. Cores were linked by snow radar and GPS surveys to provide detailed information on spatial variability in snow accumulation. Stake farm and ice core accumulation rates are observed to differ significantly, but isochrones (snow radar) correlate well with ice core derived accumulation. The accumulation/ablation pattern from stake measurements suggests that the annual local noise (metre scale) in snow accumulation can approach 2 years of ablation and more than four times the average annual accumulation, with no accumulation or ablation for a 5-year period in up to 40% of cases. The spatial variability of snow accumulation at the kilometre scale is one order of magnitude higher than temporal variability at the multi-decadal/secular scale. Stake measurements and firn cores at Dome C confirm an approximate 30% increase in accumulation over the last two centuries, with respect to the average over the last 5000 years. 2005-07-20T22:00:00Z http://hdl.handle.net/2122/4051 Title: Geophysical Survey at Talos Dome (East Antarctica) Authors: Frezzotti, M.; ENEA Progetto Clima, PO Box 2400, 000100 Roma AD - Italy; Bitelli, G.; Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, Università di Bologna, Viale Risorgimento 2, 40136 Bologna - Italy; Gandolfi, S.; Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, Università di Bologna, Viale Risorgimento 2, 40136 Bologna - Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Mancini, F.; Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, Università di Bologna, Viale Risorgimento 2, 40136 Bologna - Italy; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Vittuari, L.; Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, Università di Bologna, Viale Risorgimento 2, 40136 Bologna - Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Editors: Frezzotti, M.; ENEA Progetto Clima, PO Box 2400, 000100 Roma AD - Italy; Maggi, V.; Department of Environmental Sciences, University of Milano–Bicocca, Piazza della Scienza 1, I-20126 Milan, Italy Abstract: Talos Dome is an ice dome on the edge of the East Antarctic plateau (Fig. l), about 290 km from the Southern Ocean and 250 km from the Ross Sea. It is adjacent to the Victoria Land mountains and overlies the eastern margin of the Wilkes Subglacial Basin. To the West, an ice saddle (2260 m) divides the Dome from an ice ridge coming from Dome C. Ice flows southeastward from this ridge into outlet glaciers (Priestley, Reeves and David Glaciers) which drain into the Ross Sea, and north-westward into the Rennick and Matusevich Glaciers which drain into the Southern Ocean. Another ice ridge trends northward from the Dome, passing behind the USARP Mountain. As part of the ITASE project, two traverse surveys were carried out in the Talos Dome area in November 1996 (Frezzotti et al., 1998) and January 2002 (Frezzotti et al., this volume). Airborne radar surveys were conducted in 1997, 1999 and 2001. Research aimed to better understand the latitudinal (North-South) and longitudinal (East-West) gradient along two East-West (Talos Dome - D66) and North-South (GV7 - Talos Dome - Taylor Dome) transepts, documenting climatic, atmospheric and surface conditions in the Talos Dome area and northern Victoria Land throughout the last 200-1000 years. The study of the Talos Dome area aimed to find the best location to extract an ice core down to the bedrock. Six shallow snow-firn cores (two during 1996 and four during 2001-02), up to 90 m deep, were drilled in the Talos Dome area. An eight century-long record of volcanic signal and climatic change was obtained at Talos Dome through geochemical analysis of the deepest core (TD, 90 m deep), drilled in 1996 (Becagli et al., 2003; Narcisi et al., 2001; Stenni et al., 2002). The core was dated through seasonal variations in nss SO4 raised to the power of 2- concentrations coupled with the recognition of tritium marker level (1965-66) and the nss SO4 raised to the power of 2- spikes attributed to the most important historical volcanic events (Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Kuwae 1452, Unknown 1259). 2002-12-31T23:00:00Z