2010-10-17 19:25:22New paper on Greenland ice loss (just for something completely different)
John Cook


Sea-level fingerprint of continental water and ice mass change from GRACE


The Gravity Recovery and Climate Experiment satellites (GRACE) provide, for the first time, a method to directly measure mass exchange between the land and oceans over time. The dominant components of this exchange are due to continental ice loss/gain and land hydrology. Here, we determine the secular trend in these two components during the GRACE measurement era: 2003–2009. For each component, we model the distinct regional signatures or fingerprints of relative sea-level (RSL) change, obtaining maxima at low latitudes between ±40° N/S, but with particularly strong regional patterns. We estimate that the total ice and water mass loss from the continents is causing global mean sea-level to rise by 1.0 ± 0.4 mm/yr. Isolating the ice and hydrological signals, we find that the former is the sole net contributor to the global mean, while the latter dominates regional RSL changes in many coastal areas.

2010-10-18 09:29:26Newer Paper on Greenland Ice mass change
Robert Way


Icesat is used, extremely accurate laser altimeter, puts annual losses at 210 GT year.

"Finally, our total mass balance result is large compared to the ICESat derived mass
loss of 139±68 Gt yr−1 found by Slobbe et al. (2009), based on data from 2003 to 2007.
We believe that we have improved the application of ICESat data to estimate the total
mass balance of the GrIS, by using a novel approach including firn compaction and
5 density modelling."

They use four different methods to extract the GT change and evaluate the methods thereby concluding that one method is superior. Greenland is seen to be contributing 0.58 mm/year to sea level rise.

Wu et al. 2010 puts a much lower number but the uncertainty associated with GRACE is much greater than the uncertainty with direct elevation changes measurements such as through using icesat. If someone would just figure out how to do the boxplots for mass balance estimates I would already have an article done on the ice sheets haha... please help...

2010-10-18 09:59:04Greenland ice loss of 210 gigatonnes per year
John Cook


That's pretty consistent with Velicogna 2009 which found a rate of 137 Gt/year in 2002 increasing to 286 Gt/year in 2009.

Am really keen to read your post summarising all these latest results and putting Wu in some proper context. I'll contact Kelly O'Day who is a true guru when it comes to plotting data, maybe he can help.

2010-10-18 11:12:00Comment
Robert Way

Thanks for the tips pertaining to the boxplot via email. I'm not sure what type of plot is really the best to show this kinda data really... the uncertainties overlap so much that I guess just making a square box is the easiest but I don't know if that is the same process as a boxplot, is it?