February 2012 was the most anomalous Entinostat in vivo of the winter months in the Kara Sea, when the ice extent anomaly dropped sharply

to − 20% (Figure 7). During the winter of 2013 under the changing conditions of the large-scale atmospheric circulation in the northern hemisphere, the ice extent tended to increase in the Barents and Kara Seas (Figure 6). In the Kara Sea in February–March this parameter was close to average values (Figure 7). At the same time in the southern seas, ice conditions in February–March 2012 were anomalously severe (Figure 8). Thus, there were difficult ice conditions in the Sea of Azov, according to satellite and icebreaker data. The entire area of the sea was covered by ice (this state is observed in < 50% of winters). The ice was scarcely passable, with marked drifting, pressing and hummocking. Fast ice with a thickness from 20 cm in the Kerch Strait to 50–70 cm in Taganrog Bay formed in the coastal zone. In February–March ice thicknesses of up to 50–80 cm, and

in hummocks up to 4 m, Bortezomib were recorded in the Azov-Don Channel in the eastern part of Taganrog Bay. The large-scale thermal anomaly that spread in the first months of 2012 over the whole of Europe and the adjacent Arctic and southern seas, occurred against the background of diverse climatic tendencies. As we showed in previous papers (Matishov et al., 2009 and Matishov et al., 2011), since the beginning of the 21st century a prolonged warm anomaly has remained in the western Arctic. Comparable in intensity to ‘the Arctic warming’ in the first half of the last century, it conforms to the viewpoint of AARI specialists (Frolov et al. 2010) about the presence of a 60-year cycle governing Arctic sea ice fluctuation, and a 200-year cycle of solar radiation arriving

at the Earth. The overlap of these cycles gives grounds for considering that temperature decrease and ice growth are more likely than the warming by 2030–2040 predicted by the results of some model calculations (Kattsov & Porfiryev 2011). It is obvious that without taking into account inter-century cycles, it is impossible to analyse the climate and state of the large marine ecosystems of the North Atlantic and the Arctic. Experience of Arctic navigation has demonstrated the existence Flavopiridol (Alvocidib) of such a 60-year cycle and the warm anomalies it caused in the period not covered by regular observations. As is generally known, in 1878–1879 the expedition on board the ‘Vega’, a non-icebreaking vessel, under the leadership of A. E. Nordenskiöld sailed all the way along the Northern Sea Route, encountering impassable ice only on the way to the Bering Strait (Nordenskiöld 1887). Nowadays, the possibility of the open passage of vessels along the Northern Sea Route is being interpreted as a feature of irreversible global warming (Stephenson et al. 2013).