North Atlantic Oscillation

Meteorological conditions

During 2013, the NAO index changed from negative values in January–March to slightly positive values which lasted the rest of the year. During winter (2012 –2013) northerly, northwesterly and northeasterly winds prevailed over the Barents Sea; during summer (April–August) southerly, southwesterly, and southeasterly winds prevailed. During autumn (September–October) wind direction shifted to easterly and northeasterly.

During 2013, the number of days with winds more than 15 m/s was much higher than the long-term average, and in the eastern Barents Sea was the highest since 1981. Figure 4.2.1 indicates that the winter NAO went from strongly positive in 2012 to negative in 2013. Despite this, mean air temperatures during 2013 over the western and eastern Barents Sea indicated prevailing positive anomalies with the highest values (up to 5°C) in the eastern Sea during January, February, and April (Table 4.2.1).

Figure 4.2.1. Winter North Atlantic Oscillation (NAO) index during 1951–2013.Figure 4.2.1. Winter North Atlantic Oscillation (NAO) index during 1951–2013.

Table 4.2.1. Monthly mean air temperature anomalies at weather stations located in the Barents Sea between December 2012 and December 2013, the yearly mean anomalies in 2013, maximum anomalies, and years when they were observed. Anomalies were calculated relative to the period 1981–2010.