Wednesday, 13 February 2013

PIOMAS Vindicated!

The new paper from the Cryosat II team is being reported across the web. Rather than launch into another one of my long posts, I'll link to Neven who's done the honours here. That thread will be worth following, at least one person commenting there seems to have the actual paper, which I'm trying to get hold of (for free) before I buy it.


Anonymous said...

As the winter loss is 9%, wouldn't this mean at least 25% of the total melt is from warmed ocean currents (9% of the max loss of 36%). But the Greenhouse effect is stronger in winter so that might be a slight over-estimate. (assuming there is constant export of ice)

Chris Reynolds said...

Hi Anon,

I don't think it's that simple. Much of the volume loss has been from loss of thicker ice, but that's due to the long lifespan of such ice. Thinner younger ice bounces back every winter, so proportionately its contribution to overall volume has increased. None of which tells us what fraction of the volume loss is due to what factor (e.g. ocean/atmosphere).

The difference between summer and winter tells us that seasonal melt is going up. This could be due to ocean or atmosphere, although recent behaviour suggests that the transition to a mainly young ice pack is a major recent factor, therefore must be a factor in the past. However you are correct that winter loss is probably due to a combination of ocean and atmosphere forcing, together with imbalances between ice growth and ice loss within preceding seasons.

Given that PIOMAS is continuing to perform well I think that attribution studies using it are the best prospect for teasing out the contributions from ocean and atmosphere, and how these change over time. This isn't something I can attempt with the available gridded data.

The ocean heat flux role intrigues me, I doubt it's as great a factor as some claim, and still see the recent acceleration as being due largely to ice properties changing and the Arctic Dipole.