If Laxon et al get difference of <0.1m then couldn't an alternative explanation be that as ice gets thinner while snow remains similar (possibly increases slightly) the density that should be used changes over time such that 925kgm-3 is a sensible value for 2009, 915 sensible for 2011, while in 2013 a more sophisticated 917 / 882 split for FYI / MYI is sensible.
Snow is a big problem. It was already discussed in this thread. I speculate it is also the main reason why there has been no Cryosat-2 data reported yet for the Antarctic (where snow is often thicker than the ice).
I am still left feeling I don't know if the method is an improvement or not.
It seems that Cryosat2 volume is likely to be fairly similar to what has been previously reported (not 1m thinner).
Even if no better data on thickness and volume come out of it, the advantages of getting the freeboard right are huge:
- better constraints on snow;
- better constraints on ice densities;
These have important impacts on ice forming and melting and as such will improve the modelling. In other words helps us to understand better what is going on.
Think of it, density depends mostly on the salt contents (brine inclusion). That influences the melting point, the mechanical properties but also the porosity of ice: forming and draining of melt pools.
Further Cryosat-2 data is seen as a vindication of PIOMAS. That may not be as strong as it looked if this paper has it right.
These guys with their new method have already identified a slight misalignment of the satellite (nadir is not exactly nadir). Even looks like this is worthy stuff.
Would a comment on the paper something like the following be sensible?
Commenting is open until 21st of March, there is some time.
I think from science pov, these guys have covered the issues. Yet a clarification that the big 1.5m
improvement does not translate into similar Cryosat's new estimate seems in order (to avoid misunderstandings).