According to my contact at the PSC the model seems to be mostly ignoring the bad NSIDC ice concentration data, but they can’t say for sure that this isn’t affecting the results. We will perhaps have more certainty next month as the NSIDC is busy fixing the issue.
I expected the monthly change to be slightly negative, but it was slightly positive. This means that 2016 is still trailing record low 2011 for this time of year, but the difference went from 196 to 76 km3, and has now become so small that they are practically on a par. The difference with other years became smaller in both directions, but the difference with 2012 has increased to 741 km3. As of April 30th volume is 1719 km3 lower than it was last year, at the height of the rebound.
Here's how the differences with previous years have changed since last month's PIOMAS update:
April is also the month when the annual sea ice volume max is reached, and here the difference between 2011 (lowest max on record) and 2016 is even smaller, just 40 km3:
We can clearly see on Wipneus' version of the PIOMAS volume graph how close the 2016 and 2011 trend lines are hugging each other: