Air temperature changes in the Arctic in the period 1951–2015 in the light of observational and reanalysis data

Recent air temperature changes in the high Arctic (HA) have been investigated based on mean seasonal and annual data calculated for the period 1951–2015 and for two sub-periods 1976–2015 and 1996–2015. Two kinds of air temperature data (observational and reanalysis) have been used in the research. The observational data were compared with data taken from six reanalysis products (20CRv2c, CERA-20C, ERA-Int, MERRA-2, NCEP-CFSRR, JRA-55). The scale of the HA warming for the period 1996–2015 relative to the reference period 1951–1990 reached 1.6 °C for annual mean and was greatest in autumn (1.9 °C) and in winter (1.7 °C), while it was smallest in summer (0.9 °C). Evidently, the greatest warming was observed in the Atlantic and Siberian climatic regions, while in the rest of the HA, the rate of warming was usually weaker than trends calculated for the period 1976–2015. Air temperature tendencies in all study periods 1951–2015, 1976–2015 and 1996–2015 showed a predominance of positive trends that were statistically significant at the level of 0.05. In the two latter periods, the rate of warming was on average 2–3 times faster than for the entire study period. In the HA, there has not been a slowdown in the rate of warming (“hiatus”) in the last two decades (in contrast to that which was noted for the Northern Hemisphere). Our results reveal that, in most cases, the closest fit to observations was obtained for two reanalysis products (the ERA-Interim and JRA-55, since 1979) and the six reanalysis average. Two new polar amplification (PA) metrics based on scaled and standardised values of surface air temperature (SAT) reveal the non-existence of this phenomenon in the period 1951–2015. One of the metrics shows very small PA in the periods 1976–2015 and 1996–2015.