Cyclical structure and the prerequisites for forecasting of the duration of Arctic invasions for the next decade

The Duration of Arctic Invasions (DAI) is known to be connected with various climatological indexes. This paper presents the results of a study of DAI changes in various sectors of the Northern Hemisphere from 1899 to 2017. To this end, we used the classification of circulating mechanisms of the Northern Hemisphere by B.L. Dzerdzeevsky. The basic attention was paid to the study of the trend component of the temporal variability of the duration of Arctic invasions; to the assessment of long-period cyclic fluctuations of the DAI; and to the forecasting the duration of Arctic invasions over the next decade in the Northern Hemisphere sectors. To analyze the components of the change in the duration of Arctic invasions and its forecast, we used: a description of the initial data using a linear trend, approximation of time series by the Savitsky-Golay method, spectral analysis and spectral-time analysis, as well as the component-harmonic method. We found a significant increase in the duration of Arctic invasions in the Pacific and Atlantic sectors and its significant decline in the European and American sectors. In deviations from the trend, a powerful quasi-fifty-year component for five sectors is clearly manifested; whereas in the European sector the deviation is rather weak and quasi-thirty-year fluctuations dominate here. What is more, quasi-20-year fluctuations in the variability of DAI were revealed, we predict DAI estimates for the next 10 years by combining the trend and two quasi-cyclic fluctuations. According to our forecast an increase in the duration of Arctic invasions will occur from 2022 in the European sector. In the Atlantic sector, DAI growth will begin in 2019 and continue until 2023, and then DAI will fall. In other sectors, there will be a decrease in the duration of Arctic invasions starting from 2016. The decrease in American sector starts only from 2022.