ICESAT Data Shows Mass Gains of the Antarctic Ice Sheet Exceed Losses

The results of ICEsat measurements are in for Antarctica, and it seems those claims of ice mass loss in Antarctica have melted now that a continent wide tally has been made. This was presented in the SCAR ISMASS Workshop in Portland, OR, July 14, 2012 and was added to NASA’s Technical Reports server on September 7th, 2012. H/T to WUWT reader “Brad”. What’s interesting (besides the result) is that the report was prepared by Jay Zwally, whose “ice free Arctic by the end of summer 2012” prediction is about to be tested in 12 days.  It also puts the kibosh on GRACE studies that suggested a net loss in Antarctica. Note there’s the mention of the “climate warming, consistent with model predictions” at the end of the report. They’d say the same thing if ICEsat had measured loss instead of gain, because as we’ve seen before, almost everything is consistent with warming and models no matter which direction it goes.

Here’s the video presentation. The report abstract follows.

Mass Balance of the Antarctic Ice Sheet 1992-2008 from ERS and ICESat: Gains exceed losses – Presented by Jay Zwally, NASA Goddard, USA ISMASS 2012 is an activity of the renewed SCAR/IASC ISMASS expert group, which focuses on the mass balance of ice-sheets and their contribution to sea level changes. The workshop is sponsored by ICSU, SCAR, IASC, WCRP, IGS, and IACS with support from CliC and APECS. Video recording and editing provided by Kristin Poinar, Mai Winstrup, and Jenny Baeseman

Mass Gains of the Antarctic Ice Sheet Exceed Losses

Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David

Abstract:

During 2003 to 2008, the mass gain of the Antarctic ice sheet from snow accumulation exceeded the mass loss from ice discharge by 49 Gt/yr (2.5% of input), as derived from ICESat laser measurements of elevation change. The net gain (86 Gt/yr) over the West Antarctic (WA) and East Antarctic ice sheets (WA and EA) is essentially unchanged from revised results for 1992 to 2001 from ERS radar altimetry.

Imbalances in individual drainage systems (DS) are large (-68% to +103% of input), as are temporal changes (-39% to +44%). The recent 90 Gt/yr loss from three DS (Pine Island, Thwaites-Smith, and Marie-Bryd Coast) of WA exceeds the earlier 61 Gt/yr loss, consistent with reports of accelerating ice flow and dynamic thinning. Similarly, the recent 24 Gt/yr loss from three DS in the Antarctic Peninsula (AP) is consistent with glacier accelerations following breakup of the Larsen B and other ice shelves. In contrast, net increases in the five other DS of WA and AP and three of the 16 DS in East Antarctica (EA) exceed the increased losses.

Alternate interpretations of the mass changes driven by accumulation variations are given using results from atmospheric-model re-analysis and a parameterization based on 5% change in accumulation per degree of observed surface temperature change. A slow increase in snowfall with climate warming, consistent with model predictions, may be offsetting increased dynamic losses.

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Looks like “Skeptical Science” will have to update their reliance on the “Cophagen Diagnosis” as well as their claim of “Antarctica is losing land ice as a whole, and these losses are accelerating quickly.”:

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Figure 2: Estimates of Total Antarctic Land Ice Changes and approximate sea level contributions using many different measurement techniques. Adapted from The Copenhagen Diagnosis. (CH= Chen et al. 2006, WH= Wingham et al. 2006, R= Rignot et al. 2008b, CZ= Cazenave et al. 2009 and V=Velicogna 2009)

Estimates of recent changes in Antarctic land ice (Figure 2) range from losing 100 Gt/year to over 300 Gt/year. Because 360 Gt/year represents an annual sea level rise of 1 mm/year, recent estimates indicate a contribution of between 0.27 mm/year and 0.83 mm/year coming from Antarctica. There is of course uncertainty in the estimations methods but multiple different types of measurement techniques (explained here) all show the same thing, Antarctica is losing land ice as a whole, and these losses are accelerating quickly.

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I’m glad that’s finally settled.

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