Cyclones entering the Arctic are examined and their role in transporting moisture into the Arctic is investigated.
Using vorticity as a measure of the cyclonic activity, the activity is most vigorous in the Greenland Sea during all seasons, except summer, when the Norwegian to Kara Sea have a comparable amount of activity. The number of cyclones travelling into the Arctic is similar in all seasons, but with winter cyclones being more intense and shorter lived than during summertime. The mean residence time of cyclones entering the polar cap is 2.6 d. There is a positive trend in cyclone activity for cyclones entering the Arctic that is statistical significant in three of four seasons.
Significant correlations were found between total cyclone activity (cyclones entering Arctic) and total moisture transport into the Arctic during winter, autumn and spring. However, total cyclone activity is not the main predictor. The moisture transport variability is mainly driven by variability in cyclone activity over the Greenland Sea and East Siberian Sea; these regions together account for 55% of the variability of the total annual moisture transport. Estimates of the effect of cyclone variability in different regions on the total moisture transport are given for all seasons.