Friday 6 April 2012


PIOMAS March volume data is now out, as anticipated the daily anomalies show nothing special with volume tracking close to last year. The following graph is of daily volume anomalies, I've calculated the average for each day from 1980 to 1999, the value plotted on the graph is the difference from the average. Click on the graph to see the years, the general trend is down, with 2010 and 2011 showing the greatest drops, 2012 so far being the incomplete purple line.

The first indications of whether we'll see another anomalous volume drop this Spring will come early May when the PIOMAS volume data is out for April. Will see see another drop? If we do, what will that mean?
Once is happenstance. Twice is coincidence. The third time it's enemy action.
The anticipation is killing me...


Neven said...

It is exciting, isn't it?

I've finally made a graph that shows average thickness, by dividing PIOMAS volume by CT area. And there too 2010 and 2011 clearly stand out.

Neven said...

A second comment to receive notification of follow-up comments. Please ignore.

Lazarus said...

Anticipation indeed. So far 2012 is following last year but will the drop still follow 2011 or will it go even lower? Will it make some recovery?

A recovery is unlikely - it has never really happened except with the very exceptional 2007. 2010 could also be considered exceptional - until 2011.

Chris Reynolds said...


As I've been discussing over at your blog with Crandles; when thickness doesn't drop as volume does it implies that the volume drop is largely accounted for by change in area. As your graph shows there's been a thickness drop, that implies that the change in PIOMAS volume cannot be accounted for by change in area alone.

Calculated thickness has to be used with caution, as both you and I have noted. However it does allow some diagnosis of where the volume loss is coming from.


If you look at the graphic in the main post you'll see that Spring volume losses have been an increasing feature of recent years. It's just that in 2010 and 2011 it has been of a different order. While I can see a case that 2010's loss was due to weather, I don't see such a case for 2011. Based on the behaviour of years prior to 2010, and the repeat of 2011, I expect this year to show the same massive loss. If I didn't I wouldn't find the anticipation so trying.

Neven said...

Chris, it's difficult for me to theorize about these things like you and crandles do (maybe I should change my name to Chris ;-) ), but for now I think you have covered everything and we just have to await Spring tidings.

For what caused the 2011 drop: did you consider heat flux from the oceans? I still haven't got a (numerical) handle on that.

Chris Reynolds said...

Yes Neven, I have considered ocean heat flux.

PIOMAS is driven by the atmospheric state as represented by NCEP/NCAR, the ocean element is driven by assimilation of sea ice concentration and SSTs. There is no specific 'forcing' by externally specified ocean currents.

So any ocean forcing has to be driven by atmospheric forcing - in this case winds. I've looked at NCEP/NCAR, and haven't found a common link between 2010 and 2011. There was a persistent high pressure and warm anomalies over April to June 2010. I'd been pondering increased insolation due to clear skies. However the Arctic is still ice covered, so actually I've been rather dense. More insolation even if it lead to more surface melt wouldn't lead to higher temperatures as the ice would 'peg' temperature to zero.

I think I need to go through NCEP/NCAR at a finer time resolution and look for meridional airflows bringing in warmer air that may also increase influx of water through the Bering Strait. The Atlantic is possible but it's much saltier so being denser sinks below the cold cap of surface water that then insulates the sea-ice from the Atlantic layer.