1999).

This process partly normalises the meridional SST gradient, together with the Venetoclax order moderating effect of the northern Adriatic sub-basin, and may explain why the SST is lower in the central than the northern Adriatic sub-basin in spring and summer. Moreover, the SST gradient over the southern Adriatic sub-basin increases meridionally from west (18.2 °C) to east (18.9 °C) in autumn. However, in the northern Adriatic sub-basin in autumn, the central part was much colder than the northern part owing to the moderating effect of the north part of the sub-basin. The SST gradient over the Aegean sub-basin is significantly affected by water exchange, with cold/fresh Black Sea water entering through the Dardanelles Strait and warm/saline Levantine basin water entering through the Cretan Arc Straits. This is in agreement with the previous findings of Zervakis et al. (2000), Shaltout & Omstedt (2012) and Poulain et al. (2012). The SST gradient displays a marked seasonal variability. In winter, the Aegean SST increases from the north-western GSK-3 inhibitor part of the sub-basin (13 °C) to the south-east (16.3 °C). In spring and autumn, the Aegean SST decreases zonally from north to south, while in summer it displays a semicircular distribution centred near Lesbos Island (22.2 °C), where the SST increases with distance from

the island. The much colder Aegean area occurs along the northern Aegean coast in cold seasons, then migrates south to the eastern part of the Dardanelles Strait in spring and farther south to Lesbos Island in summer. The Aegean SST is much lower than at the same latitude in the northern Ionian sub-basin, most markedly in summer, partly due to the Etesian winds. These winds are cold and dry (Metaxas & Bartzokas 1994) and blow over the Aegean Sea in summer, north-easterly in the northern Aegean and northerly in the southern

Aegean (Kotroni et al. 2001). The Etesian winds thus moderate the Aegean SST in summer. In summer, the Aegean SST is much lower than the higher latitude Adriatic sub-basin SST, partly due to the moderating effect of the cold and dry Etesian PJ34 HCl winds. The Levantine sub-basin SST increases from north-west to south-east in autumn and winter, and increases meridionally from west to east in spring. In summer, however, the SST increases zonally from north to south over the eastern and meridionally from west to east over the western Levantine sub-basin. The Cretan Cyclone south-east of the Cretan Passage is well defined in autumn and winter (cold core, 19 °C in autumn and 15.2 °C in winter) and influences the SST all the year round. The core of the Cretan Cyclone displays a less significant warming trend than does the surrounding area in winter, indicating the continuation and increasing intensity of the Cretan Cyclone, and hence of Levantine deep water formation, in future winters.