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Scarchilli, C.
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Scarchilli, C.
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- PublicationRestrictedEffect of blowing snow on surface mass balance of East Antarctica(2010-05-02)
; ; ; ;Frezzotti, M.; ENEA, Laboratory for climate observations, Roma, Italy ;Scarchilli, C.; ENEA, Laboratory for climaDipartimentote observations, Roma, Italy and ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; In the convergence slope/coastal areas of Antarctica, a large fraction of snow is continuously eroded and exported by wind to the atmosphere and into the ocean. The extreme environmental conditions and remote location of Antarctica have long inhibited the systematic study of its climate and snow accumulation processes. Measurement of blowing snow in Antarctica is very difficult and limited, and data are only available for a few sites. Atmospheric models estimate that the horizontal divergence of snow by wind transport is of minor significance for integrated ice sheet surface mass balance because the model simulations assume that katabatic winds tend to remove mass from the interior regions of the continent and displace it to coastal/convergence areas. Moreover, the blowing snow process and direct export into the ocean are not explicitly included in numerical weather forecasting and general circulation models. Blowing snow transport and erosion from instruments, snow radar and satellite images were acquired in East Antarctica. Extensive presence of ablation surface (blue ice and wind crust) upwind and downwind of the measurement site suggest that the combine processes of blowing snow sublimation and snow transport remove up to 50% of the precipitation in the coastal and slope convergence area. These phenomena represent a major negative effect on the snow accumulation, and they are not sufficiently taken into account in studies of surface mass balance. The observed wind-driven ablation explains the inconsistency between atmospheric model precipitation and measured snow accumulation value.327 39 - PublicationOpen AccessThe Impact of Precipitation and Sublimation Processes on Snow Accumulation: Preliminary Results(2008-07)
; ; ; ; ; ; ; ; ; ;Scarchilli, C.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Speciale Clima Globale’, Rome - Italy ;Frezzotti, M.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Speciale Clima Globale’, Rome - Italy ;Didonfrancesco, G.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Speciale Clima Globale’, Rome - Italy ;Valt, M.; A.R.P.A.V., Centro Valanghe di Arabba, Livinallongo del Col di Lana (Belluno) - Italy ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;De Silvestri, L.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Speciale Clima Globale’, Rome - Italy ;Dolci, S.; Consiglio Nazionale delle Ricerche, Rome - Italy ;Iaccarino, A.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Speciale Clima Globale’, Rome - Italy ;Grigioni, P.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Speciale Clima Globale’, Rome - Italy; ; ; ; ; ; ; ; The need for climate change prediction has focused attention on the Surface Mass Balance (SMB) of the Antarctic continent and on how it influences the sea level. The SMB of the Antarctic plateau is governed by the equilibrium between precipitation and ablation processes such as sublimation and wind-borne snow redistribution. At scales of hundreds of kilometres snowfall variability dominates the snow accumulation process (Dery and Yau, 2002); at smaller scales, postdepositional process such as wind-borne redistribution, surface sublimation and snowdrift sublimation becomes more important. In recent years the sublimation phenomenon has received much attention from the glacial-meteorological community, and some theoretical studies have tried to model it (Bintanja, 1998; Dery & Yau, 2001b; Frezzotti, 2004). There are two different types of sublimation: surface sublimation and blowing snow sublimation. Surface sublimation is mostly determined by the continual exchange of water between the air (in the vapour phase) and the snow pack (in the solid phase) due to solar irradiance. Blowing snow sublimation is possibly the more effective of the two sublimation processes. It occurs when snow particles at the surface are blown by winds exceeding a certain threshold value. Particles suspended in the sub saturated Atmospheric Boundary Layer (ABL) sublimate at a relatively fast rate, cooling air mass transported by the wind and increasing the local atmospheric moisture content. When the first few meters of the ABL are completely saturated, the process is dumped. It takes a long time to meet this condition because katabatic winds transport saturated air masses to the coast, thereby reactivating sublimation. The role of sublimation in snow accumulation and its high variability at local scales are not fully understood due to the few available measurements in Antarctica. Further study and field experiments are required.304 219 - PublicationOpen AccessA synthesis of the Antarctic surface mass balance during the last 800 yr(2013-02-20)
; ; ; ; ; ;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; ; ; ; 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.693 529 - PublicationOpen AccessHistorical behaviour of Dome C and Talos Dome (East Antarctica) as investigated by snow accumulation and ice velocity measurements(2008-02)
; ; ; ; ; ; ; ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Frezzotti, M.; enea casaccia ;Gandolfi, S.; università di bologna ;Vincent, C.; LGGE Grenoble ;Scarchilli, C.; enea casaccia ;Vittuari, V.; università di bologna ;Fily, M.; LGGE Grenoble; ; ; ; ; ; Ice divide–dome behaviour is used for ice sheet mass balance studies and interpretation of ice core records. In order to characterize the historical behaviour (last 400 yr) of Dome C and Talos Dome (East Antarctica), ice velocities have been measured since 1996 using a GPS system, and the palaeo-spatial variability of snow accumulation has been surveyed using snow radar and firn cores. The snow accumulation distribution of both domes indicates distributions of accumulation that are non-symmetrical in relation to dome morphology. Changes in spatial distributions have been observed over the last few centuries, with a decrease in snow accumulation gradient along the wind direction at Talos Dome and a counter-clockwise rotation of accumulation distribution in the northern part of Dome C. Observations at Dome C reveal a significant increase in accumulation since the 1950s, which could correlate to altered snow accumulation patterns due to changes in snowfall trajectory. Snow accumulation mechanisms are different at the two domes: a wind-driven snow accumulation process operates at Talos Dome, whereas snowfall trajectory direction is the main factor at Dome C. Repeated GPS measurements made at Talos Dome have highlighted changes in ice velocity, with a deceleration in the NE portion, acceleration in the SW portion and migration of dome summit, which are apparently correlated with changes in accumulation distribution. The observed behaviour in accumulation and velocity indicates that even the most remote areas of East Antarctica have changed from a decadal to secular scale.348 645 - PublicationRestrictedSpatial and temporal variability of surface mass balance near Talos Dome, East Antarctica(2007)
; ; ; ; ; ;Frezzotti, M.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, Rome, Italy ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Proposito, M.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, Rome, Italy ;Scarchilli, C.; Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, Rome, Italy - Dipartimento di Scienze della Terra, University of Siena, Siena, Italy ;Gandolfi, S.; Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, University of Bologna, Bologna, Italy; ; ; ; Predictions concerning Antarctica’s contribution to sea level change have been hampered by poor knowledge of surface mass balance. Snow accumulation is the most direct climate indicator and has important implications for paleoclimatic reconstruction from ice cores. Snow accumulation measurements (stake, core, snow radar) taken along a 500-km transect crossing Talos Dome (East Antarctica) have been used to assess accumulation signals and the representativeness of ice core records. Stake readings show that accumulation hiatuses can occur at sites with accumulation rates below 120 kg m 2 yr 1. Differences between cores and stakes can lead to statistical misidentification of annual layers determined from seasonal signals at sites with accumulation rates below 200 kg m 2 yr 1 because of nondetection of higher and lower values. Achieving ±10% accuracy in the reconstruction of snow accumulation from single cores requires high accumulation (750 kg m 2 yr 1). Low-accumulation sites are representative if cumulative rates computed over several years are used to reach the 750 kg m 2 yr 1 threshold. Temporal variability of accumulation over the last two centuries shows no significant increase in accumulation. Wind-driven processes are a fundamental component of surface mass balance. Spatial variations in accumulation are well correlated with surface slope changes along the wind direction and may exceed 200 kg m 2 yr 1 within 1 km. Wind-driven sublimation rates are less than 50 kg m 2 yr 1 in plateau areas and up to 260 kg m 2 yr 1 in slope areas and account for 20–75% of precipitation, whereas depositional features are negligible in surface mass balance.253 19