General comment

The paper investigates potential source regions and ice-related factors affecting size distributions and newly formed particles in Arctic based on measured size distributions during five cruises of I/B Oden in the summers of 1991, 1996, 2001, 2008, and 2018. The topic is of interest and suitable for the Journal. A few aspects should be made more clear in a revision step, see my specific comments.

Specific comments

Section 2.2, lines 160-165. I understand that details are given in other papers, however, it would be useful to summarise here what instruments are used and their sizer range. In addition, if the different instruments have been compared one with the other and if size distribution of dried (i.e. low RH) air was measured.

Section 2.3 Do you have any idea of the boundary-layer height. I was wondering if the arrival height was above or within the boundary layer.

Figures 1 and 3 are very small to be readable. Authors should considering using a different layout.

Section 4. How the new particle formation events were determined? Or the discussion only consider small particles as newly formed?

Figure 8. What is the meaning of the peak around 100% visible in each graph?

Figure 12 and correlated discussion. It seems that there are very large differences between median values and average. This are likely due to large values influencing the average. However, the conclusions obtainable from media would be significantly different compared to those of average. Could you please comment in more detail this aspect. It could be useful to show a comparison of the incidence of new particle formation events in the two cases: melt and freeze-up periods.

my review is attached as a supplement.