Massimo Frezzotti Æ Michel Pourchet Æ Onelio Flora Stefano Gandolfi Æ Michel Gay Æ Stefano Urbini Christian Vincent Æ Silvia Becagli Æ Roberto Gragnani Marco Proposito Æ Mirko Severi Æ Rita Traversi Roberto Udisti Æ Michel Fily New estimations of precipitation and surface sublimation in East Antarctica from snow accumulation measurements Received: 27 November 2003 / Accepted: 22 May 2004 / Published online: 8 September 2004 Ó Springer-Verlag 2004 Abstract Surface mass balance (SMB) distribution and its temporal and spatial variability is an essential input parameter in mass balance studies. Different methods were used, compared and integrated (stake farms, ice cores, snow radar, surface morphology, remote sensing) at eight sites along a transect from Terra Nova Bay (TNB) to Dome C (DC) (East Antarctica), to provide detailed information on the SMB. Spatial variability measurements show that the measured maximum snow accumulation (SA) in a 15 km area is well correlated to firn temperature. Wind-driven sublimation processes, controlled by the surface slope in the wind direction, have a huge impact (up to 85% of snow precipitation) on SMB and are significant in terms of past, present and future SMB evaluations. The snow redistribution pro- cess is local and has a strong impact on the annual variability of accumulation. The spatial variability of SMB at the kilometre scale is one order of magnitude higher than its temporal variability (20–30%) at the centennial time scale. This high spatial variability is due to wind-driven sublimation. Compared with our SMB calculations, previous compilations generally over-esti- mate SMB, up to 65% in some areas. 1 Introduction Precipitation over Antarctica is recognised as an important climate variable. Snow accumulation (SA) rate or surface mass balance (SMB) on the Antarctic Plateau is the sum of precipitation, sublimation/deposi- tion and wind-blown snow. Large gaps in observations mean that any estimate of the current mass input in- volves a large error factor (Genthon and Krinner 2001; Rignot and Thomas 2002). Spatial SMB is known to vary greatly (e.g. Richardson et al. 1997; van den Broeke et al. 1999; Frezzotti et al. 2002a; Frezzotti et al., in press). Representative observations of the SMB are important in estimating the characteristics of spatial and temporal variability at local scales (<10 km 2 ) and at the scale of a drainage basin. Snow redistribution changes the topography, and the topography in turn alters the wind field in a feedback system between the cryosphere and atmosphere. On the local scale, there is continual interaction between processes such as wind, snow pre- cipitation, sublimation and SMB variations; in particu- lar, the surface-energy balance and katabatic wind patterns are closely inter-related. Antarctica is the highest and flattest of the Earth’s continents, but small changes in slope have a strong impact on wind direction and speed (Frezzotti et al. 2002a). It has long been known that slope and curvature can play an important role in the SMB; for example, concave depressions accumulate snow at the expense of convex rises (Black and Budd 1964; Whillans 1975; Pettre´ et al. 1986; van den Broeke et al. 1999; Liston et al. 2000; Frezzotti et al. 2002a). A large area of the plateau, where the slope along the wind direction is M. Frezzotti (&) Æ R. Gragnani Æ M. Proposito Ente per le Nuove Tecnologie, l’Energia e l’Ambiente, ‘Progetto Clima Globale’, Rome, Italy E-mail: frezzotti@casaccia.enea.it M. Pourchet Æ M. Gay Æ C. Vincent Æ M. Fily Laboratoire de Glaciologie et Ge´ophysique de l’Environnement, CNRS, Saint Martin d’He`res, France O. Flora Dipartimento di Scienze Geologiche, Ambientali e Marine, University of Trieste, Trieste, Italy S. Gandolfi Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, University of Bologna, Bologna, Italy S. Urbini Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy S. Becagli Æ M. Severi Æ R. Traversi Æ R. Udisti Dipartimento di Chimica, University of Florence, Florence, Italy Climate Dynamics (2004) 23: 803–813 DOI 10.1007/s00382-004-0462-5