This link to an old map that was posted over on melting season thread reminded me of some very interesting old maps from DMI. They seem to have made an annual report showing the ice edge in the months leading up to the minimum (i.e. April to August), but not all the old reports are available online.
Interestingly, these maps very rarely show a polynya in the Laptev Sea.
It is also curious that until the 21st century, no one could pass the northeast passage without an icebreaker in one summer.
At best, such attempts ended in wintering in the East Siberian Sea, where the ice has always melted the longest.
For example, the expedition of 1878: