Chemical and isotopic snow variability in East Antarctica along the 2001/02 ITASE traverse Silvia BECAGLI, 1 Marco PROPOSITO, 2,4 Silvia BENASSAI, 1 Onelio FLORA, 3 Laura GENONI, 3 Roberto GRAGNANI, 4 Ombretta LARGIUNI, 1 Simone Luca PILI, 4,5 Mirko SEVERI, 1 Barbara STENNI, 3 Rita TRAVERSI, 1 Roberto UDISTI, 1 Massimo FREZZOTTI 4 1 Chemistry Department – Analytical Chemistry, Scientific Pole, University of Florence, Via della Lastruccia 3, I-50019 Sesto Fiorenti (Florence) Italy E-mail: silvia.becagli@unifi.it 2 Museo Nazionale dell’Antartide, Strada del Laterino 8, I-53100 Siena, Italy 3 Department of Geological, Environmental and Marine Sciences, Universityof Trieste, Via E. Weiss 2, 1-34127, Trieste, Italy 4 ENEA, Centro Ricerche, Casaccia, PO Box 2400, I-00100 Rome, Italy 5 Department of Earth Science, University of Cagliari, Via Trentino 51, 1-09127 Cagliari, Italy ABSTRACT. As part of the International Trans-Antarctic Scientific Expedition (ITASE) project, a traverse was carried out from November 2001 to January 2002 through Terre Ade ´ lie, George V Land, Oates Land and northern Victoria Land, for a total length of about 1875km. The research goal is to determine the latitudinal and longitudinal variability of physical, chemical and isotopic parameters along three transects: one west–east transect (WE), following the 2150 m contour line (about 400 km inland of the Ade ´lie, George V and Oates coasts), and two north–south transects (inland Terre Ade ´lie and Oates Coast–Talos Dome–Victoria Land). The intersection between the WE and Oates Coast–Victoria Land transects is in the Talos Dome area. Along the traverse, eight 2m deep snow pits were dug and sampled with a 2.5 cm depth resolution. For spatial variability, 1m deep integrated samples were collected every 5km (363 sampling sites). In the snow-pit stratigraphy, pronounced annual cycles, with summer maxima, were observed for nssSO 4 2– , MSA, NO 3 – and H 2 O 2 . The seasonality of these chemical trace species was used in combination with stable-isotope stratigraphy to derive reliable and temporally representative snow-accumulation rates. The study of chemical, isotopic and accumulation-rate variability allowed the identification of a distribution pattern which is controlled not only by altitude and distance from the sea, but also by the complex circulation of air masses in the study area. In particular, although the Talos Dome area is almost equidistant from the Southern Ocean and the Ross Sea, local atmospheric circulation is such that the area is strongly affected only by the Ross Sea. Moreover, we observed a decrease in concentration of aerosol components in the central portion of the WE transect and in the southern portion of the Talos Dome transect; this decrease was linked to the higher stability of atmospheric pressure due to the channelling of katabatic winds. INTRODUCTION The aim of the International Trans-Antarctic Scientific Expedition (ITASE) programme is the study of the spatial variability and evolution over time (last 200 years) of parameters related to the atmospheric system, and recorded in the snowfall and upper layers of the Antarctic ice sheet (Mayewski and Goodwin, 1999). These data can be used to assess recent environmental changes in the drainage area extending from Dome Concordia (Dome C) to the Ross Sea and the Southern Ocean. A detailed database is essential for determining the spatial significance of trends in the chemical and isotopic com- position of surface snow. This information allows a better understanding of the effects of atmospheric conditions, air mass circulation and the strength and direction of dominant winds on the chemical and isotopic composition of snow. Moreover, such knowledge is essential for interpreting temporal changes in the vertical chemical profiles of deep ice cores drilled in this area. Due to the scarcity of climatological and glaciological data for some interior regions of the Antarctic continent, high-spatial-resolution records from inland sites are extremely important for understanding the chemical–physical processes that deter- mine the concentration of chemical species as a function of altitude, distance from the sea, accumulation rates and other glaciological and climatological conditions. The concentrations of the main ionic components can provide information about relative contributions of different atmospheric aerosol sources. The study of changes in chemical composition as a function of altitude and distance from the sea allows a better understanding of atmospheric aerosol transport and depositional processes. Given that accumulation rates can modify the original composition of chemical markers in snow, by dilution (in case of dominant dry deposition: Legrand and Mayewski, 1997) and post-depositional effects (particularly for volatile and unstable species like HCl, HNO 3 and H 2 O 2 : McConnell and others, 1998; Ro ¨thlisberger and others, 2000; Traversi and others, 2000), it is necessary to understand if and where these potential palaeomarkers can be used to reconstruct the composition of past atmospheres. Annals of Glaciology 39 2004 473