Starting in 1988, a large amount of thick multi-year ice began flowing out of the Arctic Basin into the Fram Strait during the winters. This caused the ice to thin.
Since 2009, the pattern has reversed and the percentage of multi-year ice has increased substantially, causing the ice to thicken. This past winter the thick ice moved directly away from the Fram Strait, causing almost all of it to be preserved.
The amount of 2+ year old ice has increased by 30% since 2009, and the amount of 3+ year old ice has increased by 50% since 2011. People at NSIDC understand this, but for some reason Mark Serreze isn’t talking about it.
Winter winds caused the decline, and they are also causing the increase. PIOMAS of course does not reflect any of this.