Advances in Oceanography and Limnology Vol. 2, No. 1, June 2011, 55–77 Climatology and decadal variability of the Ross Sea shelf waters A. Russo ab , A. Bergamasco b , S. Carniel b * , L. Grieco ad , M. Sclavo b and G. Spezie c a Department of Marine Sciences, Polytechnic University of Marche, Ancona, Italy; b Institute of Marine Sciences, National Research Council, Venezia, Italy; c Department of Science for the Environment, ‘‘Parthenope’’ University, Napoli, Italy; d Via Iommella Piccola 59, 80065 Sant’Agnello, Napoli, Italy (Received 18 November 2010; final version received 22 March 2011) The World Ocean Database 2001 data located in the Ross Sea (named WOD01 and containing data in this region since 1928) are merged with recent data collected by the Italian expeditions (CLIMA dataset) in the period November 1994–February 2004 in the same area. From this extended dataset, austral summer climatologies of the main Ross Sea subsurface, intermediate and bottom water masses: High Salinity Shelf Water (HSSW), Low Salinity Shelf Water (LSSW), Ice Shelf Water (ISW) and Modified Circumpolar Deep Water (MCDW) have been drawn. The comparison between the WOD01_1994 climatologies (a subset of the WOD01 dataset until April 1994) and the CLIMA ones for the period 1994/95–2003/04 showed significant changes occurred during the decade. The freshening of the Ross Sea shelf waters which occurred during the period 1960–2000, was confirmed by our analysis in all the main water masses, even though with a spatially varying intensity. Relevant variations were found for the MCDW masses, which appeared to reduce their presence and to deepen; this can be ascribed to the very limited freshening of the MCDW core, which allowed an increased density with respect to the surrounding waters. Variations in the MCDW properties and extension could have relevant consequences, e.g. a decreased Ross Ice Shelf basal melting or a reduced supply of nutrients, and may also be indicative of a reduced thermohaline circulation within the Ross Sea. Shelf Waters (SW) having neutral density  n 4 28.7 Kg m 3 , which contribute to form the densest Antarctic Bottom Waters (AABW), showed a large volumetric decrease in the 1994/95–2003/04 decade, most likely as a consequence of the SW freshening. Keywords: Ross Sea oceanography; Ross Sea water masses; Ross Sea climatology 1. Introduction The polar regions are considered to be more sensitive to global warming than the lower latitude areas [1]. For this reason, although deep ocean warming has been reported worldwide [2,3], several studies have recently focused on depicting the trends of hydrological properties of high latitude oceans [4–6]. Despite limited information existing on the climatological scale for sea surface salinity variability, Reverdin et al. (2007), Rahmstorf (1995) and Hakkinen (1999) [7–9] showed that it is indisputable that sea surface salinity plays an important role at high latitudes in contributing to the variability of surface density and, in turn, affecting the intensity of the meridional circulation. *Corresponding author. Email: sandro.carniel@ismar.cnr.it ISSN 1947–5721 print/ISSN 1947–573X online ß 2011 Taylor & Francis DOI: 10.1080/19475721.2011.575179 http://www.informaworld.com