Question: By how many days per decade has the melt season lengthened in the shallowest of the world's major oceans?
Sentence (from "Arctic sea ice decline"): It has been established that the region is at its warmest for at least 40,000 years and the Arctic-wide melt season has lengthened at a rate of 5 days per decade (from 1979 to 2013), dominated by a later autumn freezeup.
Relevant evidence: Yes