By Steve Goddard
In my previous PIOMAS verification piece I noted that PIOMAS volume trends don’t correlate with extent trends over the last three years. PIOMAS has gone down since 2007, while extents have increased.
The diverging trends themselves prove nothing, because it possible (but unlikely) for it to occur. This time I directly compared calculated volume measurements, which should be more definitive.
In their current graph (below) PIOMAS shows a record negative volume anomaly.
This appears to be incorrect, because we can see from the PIPS blink maps (below) that thicknesses were generally lower on this date in 2008. If the visual impression is correct, it would be impossible for the current anomaly to be greater in magnitude than the 2008 anomaly.
Quantifying this further, I numerically integrated May 31 pixel count vs. thickness since 2000.
As you can see, May 31, 2010 volume is currently higher than any year since 2006. It is also higher than 2003. Remember that 2003 had the highest minimum of any year in the JAXA record.
So why does PIOMAS show a record volume anomaly at present? Something is wrong either with PIPS maps or published PIOMAS volume data. PIOMAS trends are widely quoted and it is important for them to be correct.
Willis has also made some interesting observations.