Hydrography of the eastern part of the Aegean Sea during the Eastern Mediterranean Transient (EMT) Erdem Sayın ⁎, Canan Eronat, Şeniz Uçkaç, Şükrü T. Beşiktepe DEU Institute of Marine Sciences and Technology, Baku Bulvarı, No 100, Inciralti, 35340 Izmir, Turkey abstract article info Article history: Received 9 December 2010 Received in revised form 23 May 2011 Accepted 22 June 2011 Available online 4 July 2011 Keywords: Hydrography Aegean Sea Water Mass Eastern Mediterranean Transient Deep Water Formation Cascading Hydrographic features of the Aegean Sea were studied using CTDs collected in 4 cruises from 1991 to 1993. This period covers an interesting large-scale change in the thermohaline circulation in the Eastern Mediterranean and the Aegean Sea known as the Eastern Mediterranean Transient (EMT) and was first described during early 1990s. The cruise data is analyzed to depict the spatial variability of the water masses of the Aegean Sea in this period. We found Levantine Waters to be particularly prominent during the spring of 1992, more than in the other seasons. In the Central Aegean Sea the circulated cold water mixes with the upwelling water and very dense water remains behind in summer 1991. The Levantine Surface Water (LSW) is blocked and does not penetrate further to the north because of the existing upwelling water seen near Saros (Buyukkemikli Cape) and off-shore side of Baba Cape (product of northerly wind) especially in summer 1991 and in fall 1992. The water masses are nearly homogeneous vertically with the influence of strong wind and convective mixing in winter time. In this study, we underline the contribution of the eastern part of the Aegean to the rising isopycnal levels during the EMT. In turn, i) the dense water cascades from eastern shelf of the Aegean Sea, ii) the upwelling and downwelling processes in the northern and central basins, iii) the cooling effect of Black Sea Water (BSW) on upwelled water at the south of the Lemnos Island (open sea convection) and iv) local wind forcing. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The Aegean Sea is connected with the Marmara Sea through the Dardanelles Strait, with the Ionian Sea through the Kithira, Antikithira and Elafonisos Straits and with the Levantine through the Rhodes, Kassos and Karpathos Straits (Fig. 1). It has more than 2000 islands forming small basins and narrow passages, and a very irregular coastline and bathymetry. The North Aegean Trough is the deepest basin in the North Aegean Sea. This deep basin is connected to the Chios basin with a sill of 350 m. In the south, the Chios basin communicates with the Cretan basin mainly through the passage between the shallow Kiklades Plateau and the west coast of Turkish Mainland. The Eastern Mediterranean Transient (EMT) which is the important period starting from 1987 and ending 1996 caused drastic changes in the water dynamics of the Mediterranean Sea (Theocharis et al. 1999). The source of Eastern Mediterranean Deep Water (EMDW) had shifted from the Adriatic to the Aegean Sea. The process has been called as the Eastern Mediterranean Transient (EMT). The EMT is discussed in relation to different factors and reasons in Zervakis et al. (2004). They reviewed the response of the Aegean Sea to climatic variability and mentioned the role of the North Atlantic Oscillation on EMT. According to Demirov and Pinardi (2002), wind stress has played an important role for the new forming EMDW. Samuel et al. (1999) analysed individual monthly wind stress fields over the Mediterranean for 1980–1993 showing an intensification of the winter mean wind stress over the Aegean Sea occurred in the latter half of this period. Velaoras and Lascaratos (2005) found abrupt increase in density in the intermediate depths during 1987 and 1988 in the Aegean Sea due to the decrease in the temperature. In 1993, an even more intense density increase was observed, characterized this time by an abrupt salinity increase, as well as a temperature drop. Gertman et al. (2006) reported that EMDW already began overflowing the sills of the Kassos and Antikithira Straits as early as during the winter of 1988. Roether et al. (2007), showed that the outflow of Aegean dense water (Cretan Deep Water, hereafter CDW) in 1993 of nearly 3 Sv and that the total outflow of CDW over the sills of Kassos and Antikithira Strait during the EMT amounted to about twice the total volume of the Aegean Sea. Levantine surface waters flowing into the Aegean Sea before 90's, could be a main triggering mechanism for EMT (Klein et al., 1999 and Roether et al., 1996). The enhanced presence of these highly saline water masses in the early 90s, presumably signifies the intrusion of high salinity water of Levantine origin into the North–Central Aegean following the massive outflow of dense Aegean water into the Eastern Mediterranean. This salinity intrusion was one of the preconditioning factors that enhanced dense water formation in the Aegean during the last major deepwater formation phase of the EMT (Velaoras and Lascaratos, 2005, 2010). Temporal evolution of the water masses of the Aegean Sea before during and after the EMT studied by Sayin and Besiktepe (2010). Journal of Marine Systems 88 (2011) 502–515 ⁎ Corresponding author. Tel.: + 90 232 278 5565; fax: + 90 232 278 5082. E-mail address: erdem.sayin@deu.edu.tr (E. Sayın). 0924-7963/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmarsys.2011.06.005 Contents lists available at ScienceDirect Journal of Marine Systems journal homepage: www.elsevier.com/locate/jmarsys