Ah, a fertile theme for post names. Excellent.
So, much excitement over a new GRACE study in Nurture (Accelerated Antarctic ice loss from satellite gravity measurements, J. L. Chen et al.) indicating that Antarctica as a whole was losing mass: In agreement with an independent earlier assessment, we estimate a total loss of 190plusminus77 Gt yr-1, with 132plusminus26 Gt yr-1 coming from West Antarctica. However, in contrast with previous GRACE estimates, our data suggest that East Antarctica is losing mass, mostly in coastal regions, at a rate of -57plusminus52 Gt yr-1, apparently caused by increased ice loss since the year 2006.
But as you’re aware, I’m obliged to be bitter and cynical about all this kind of stuff, so you must be wondering “how is he going to get out of that“. Well maybe I won’t, but I’ll try. First off though, can we please all ignore the septic dribble about Ant Mass Gain Disproves GW. We all know that is tosh, so leave it aside.
Let’s begin by quibbling their use of “long-term”: according to fig 3, 2006-9 is “long term” (and 2009 isn’t even over!). Clearly this is an abuse of the term. we may be looking at no more than a few years fluctuation. Only time will tell on that one.
Continuing, I find papers that talk only in terms oh Gigatonnes (ooh scary) annoying; I’d expect a conversion into mm of SLR at some point. I don’t see them providing that, so I’ll have to: 190 Gt/yr ~ 0.6 mm/yr. Also known as 6 cm/century. So without further acceleration this is not going to be exciting (that is why they need “acceleration” in the title).
Looking back, I see I talked about GRACE in 2006 when they only had 3 years data. That paper said “152 ± 80 km3/year of ice, equivalent to 0.4 ± 0.2 mm/year of global sea level rise”; as far as I can see the new results are within the error bounds of the old (and vice versa) so the main result of this new paper is the change, in ~2006, of the slope, rather than any vast new mass loss. As before, the PGR term is a problem: PGR model errors are probably the dominant limitation to Antarctic mass rate estimates as the paper wisely says; they can vary their answer substantially by choosing different PGR models.
That will have to do I think.