Comment on Impact of declining Arctic sea ice on winter snowfall by DocMartyn

Try the Admirality Records, the RN ran convoys to Russian from 1941 and tried to keep as close to the ice pack as possible. After WWII British and American spy ships monitored the Soviet Navy pretty much non-stop.
The USN will also have all the yearly records their submarines got of the Arctic ice.
It wasn’t until relatively recently, with the commissioning of USS San Juan (SSN-751; 1988) that US submarines were able to break through thick ice. Prior to this period, they would spend a lot of time looking at ice thickness.
So both the RN and USN have a LOT of data on ice-pack thickness and extent. You could ask really nicely.