## Latest GRACE data: record ice loss in 2010

#### Posted on 29 January 2011 by John Cook

The GRACE satellites continue to measure the change in gravity around the Greenland ice sheet. Here is the latest data showing the record amount of ice loss Greenland experienced in the 2010 summer. H/T to Tenney Naumer from Climate Change: The Next Generation and Dr John Wahr at the University of Colorado who analysed the GRACE data and granted permission to reproduce it here.

*Figure 1: Greenland ice mass anomaly - deviation from the average ice mass over the 2002 to 2010 period. Black line shows monthly values. Orange line shows long-term trend. *

As we get into strife everytime I display this graph, I will stress that this graph shows "Ice Mass *Anomaly*" - the deviation from the average value over the 9 years. So when values are positive from 2002 to 2006, this doesn't mean the ice sheet is gaining ice - quite the contrary as the curve is headed downwards. It means the ice mass is above the average value over 2002 through 2010.

It's interesting to compare this data to previous blog posts in May 2010 and November 2010. The ice loss in 2010 is the greatest in the satellite record - around 600 billion tonnes of ice mass loss over the 2010 summer. More importantly, the rate of ice loss continues to increase, more than doubling since 2002.

The GRACE satellites only started recording observations in 2002. A more long-term picture is available by combining GRACE data with a range of other estimations of Greenland ice loss which give us a 50 year picture as well as a range of independent measurement techniques:

*Figure 2: Rate of ice loss from Greenland. Vertical lines indicate uncertainty, horizontal lines indicate averaging time. Blue circles are from altimetry, red squares are from net accumulation/loss and green triangles are from GRACE. The black line is a straight-line (constant acceleration) fit through the mass balance data for the period 1996–2008 with a slope of 21 gigatonnes/yr ^{2} (Jiang 2010*

*).*

michael sweetat 18:51 PM on 29 January, 2011Alexandreat 20:29 PM on 29 January, 2011BillyJoeat 21:13 PM on 29 January, 2011lesat 21:50 PM on 29 January, 2011John Chapmanat 22:15 PM on 29 January, 2011David Hortonat 22:30 PM on 29 January, 2011fydijkstraat 00:46 AM on 30 January, 2011not accelerating. This is what can be deduced from satellite measurements.Zerothat 01:32 AM on 30 January, 2011muoncounterat 01:48 AM on 30 January, 2011RickGat 01:53 AM on 30 January, 2011pdtat 02:10 AM on 30 January, 2011Zerothat 02:15 AM on 30 January, 2011mlyleat 02:19 AM on 30 January, 2011Moderator Response:[Daniel Bailey] Thanks for the link. All further comments on sea level are off-topic here and should go on a more relevant thread (such asthis oneby reader PDT). Thanks!Daniel Baileyat 02:49 AM on 30 January, 2011Zeroth(8) Info on GRACE ishere. Ideally, the range of ice mass measurements is shown to increase the accuracy of the next measurement: the anomaly.Climate scientistsuse anomalies instead of absolutes because they are interested in thechangefrom a known reference point. This allows any signal in the data to emerge (time series of absolute measurements such as temperatures, or in this case: ice mass loss, tend to be very noisy with much variation). I also would be interested in seeing the deviation anomaly from just 2002 as a reference point. Not that it would change the graph any. The YooperZerothat 02:55 AM on 30 January, 2011Moderator Response:[Daniel Bailey] GRACE data begin in 2002, when the satellite was orbited and completed calibration. Nitty-gritty details are at the GRACE site linked earlier. The Original Post (OP) above talks about other sources of data on Greenland ice mass loss. The anomalies in the first graph show the change in mass loss over time (the rate of loss is increasing; eyeball Mk^{2}suggests a quadratic fit).michael sweetat 05:28 AM on 30 January, 2011Ron Crouchat 06:15 AM on 30 January, 2011From Peruat 10:23 AM on 30 January, 2011Moderator Response:[Daniel Bailey] You might tryhere.michael sweetat 11:04 AM on 30 January, 2011dhogazaat 11:27 AM on 30 January, 2011From Peruat 12:07 PM on 30 January, 2011Moderator Response:[Daniel Bailey] Try emailing John Wahr: John.Wahr@colorado.eduRidunaat 18:46 PM on 30 January, 2011johnhprice44at 21:25 PM on 30 January, 2011michael sweetat 21:38 PM on 30 January, 2011michael sweetat 21:58 PM on 30 January, 2011Ridunaat 10:41 AM on 31 January, 2011John Brookesat 12:00 PM on 31 January, 2011Yvan Dutilat 13:43 PM on 31 January, 2011robert wayat 17:57 PM on 31 January, 2011http://www.skepticalscience.com/Ice-Sheet-mass-loss-melting.htmfor discussion of your question.Moderator Response:[Daniel Bailey] Converted URL to link.bratislaat 20:36 PM on 31 January, 2011Bart Verheggenat 21:08 PM on 31 January, 2011peter prewettat 14:11 PM on 1 February, 2011scaddenpat 14:45 PM on 1 February, 2011Bernat 17:02 PM on 8 February, 2011Henry justiceat 07:49 AM on 22 March, 2011I wonder if the hydrostatic sinking of Greenland has been factored into the calculations. This will offset some of the sea level rise from Greenland's sea destined meltwater.

Response:[DB] Henry, I think you mean isostatic rebound. The edges of Greenland are actually rebounding upward slightly as the overburden of ice dwindles, lightening its downward load on the basement rock. Think cork bobbing up in the water (buoyant). But it's not much. And yes, it's been factored into the calculations.

scaddenpat 10:57 AM on 22 March, 2011williamat 09:58 AM on 10 September, 2012