## 3 Results
### Full Arctic Data Set  
Figures 9 and 10 summarise the full 9 year time series of CS2 SWH. Figure 9 shows that the higher wave heights are found in the North Atlantic during the winter months. This region shows a seasonal cycle with mean 4 m SWH during winter months reducing to 1-1.5 m during the summer (June to August as shown in the shaded region in Figure 10). The other perennial ice free regions--Baffin Bay, Barents, Kara, and Bering Seas--show a similar seasonal cycle with lower average SWH. The regions with a seasonal ice cover--Laptev, Beaufort and East Siberian Seas--are ice covered during the winter with no waves. From March to April onwards there is a slow increase in wave height as the sea ice retreats until there is a maximum from September to October before the sea ice advances once more. The Central Arctic and Kara Sea show a mixture of both cycles as they contain both perennial open ocean and seasonal ice.  
The North Atlantic sector shows the winter of 2015 having the highest average SWH, matched by the a peak in the Barents Sea. However the Kara Sea had lower wave heights this season, and both it and Baffin bay had higher waves during 2017, not matched by the North Atlantic. All regions with perennial open ocean have higher waves during the winter. All regions have similar average wave heights near 1 m during the summer.  
Figure 8: Detailed comparisons between our new SWH and the RADS product for data in 2014. Data has been collected onto a 100 km grid before comparison. Locations where RADS data are 0.5 m greater than our new data are omitted. The top row is for the raw data product, equivalent to that shown in Figure 5, the second row shows comparisons between the corrected RADS data and our new SWH with the mode bias removed. The columns separate between data collected in LRM and SAR mode. The green line in the top left panel represents the correction applied to the RADS data by [17]. The red lines are the linear best fit between our new data and the RADS data.  
Here we compare the extreme wave events apparent within the data set by looking at the height of the 95 th and 99 th percentiles for the winter period show in Figure 11. Whilst the 50 th percentile shows a similar pattern to the mean seasonal maps (Figure 11) the 95 th and 99 th percentiles show the distribution of high wave events. To the south west of Iceland there are high SWH's apparent in the 95 th (8 m) and 99 th percentiles (at or even above the 10 m threshold of our retracker), indicating regular high swells. In contrast in the nordic seas see near 10 m waves in the 99 th percentile but only 6 m for 95 th, showing the high but rare large swells in this area.  
In the central Arctic, the majority of ice free Beaufort sea remain sheltered, with all SWHs lower than 3 m and most less than 2. For the Chukchi and East Siberian seas, a number of rare events occur with swells from 4 to 6 m.  
Figure 9: Climatological maps of retrieved SWH (m) for **(a)** Jan. Feb. Mar., **(b)** Apr. May. Jun., **(c)** Jul. Aug. Sep., **(d)** Oct. Nov. Dec. for the years 2011–2019. Plot **(a)** indicates the regions used in Figure 10. Overlaid on each plots are the average contours of 15% 50% and 85% sea NSIDC ice concentration for that quarter. Note that the Beaufort region also encompasses the Chukchi and Bering Seas.