The PIPS video below makes it easy to understand the behaviour of Arctic ice during September.
During the first three weeks of September, southerly winds blew the ice towards the pole. This compacted and melted the thinner ice, leaving a large area of cold water where the ice used to be.
Around September 20, the winds reversed. New ice quickly formed in the regions where it had disappeared earlier in the month – despite the fact that this is the hottest year in history.
It is very easy to see the date of the wind reversal in the JAXA graph.
Close up below :
Wind is weather, not climate.