Antarctic Ice Mass — Alternate Sources

Brief Note by Kip Hansen — 6 October 2021

I am engaged in a community education program that includes a great number of climate activists and climate zealots as well as persons who are just curious and interested in improving their community’s response to weather and climate. In the process, I happened to mention in an online training session that Antarctic Ice Mass has been increasing, not decreasing over the last few decades, correcting a point made by the instructor.

The course instructor, a climate activist and educator, took exception to this correction. I was, however, confident in my position, though I had not reviewed the issue for years — thus, was a little unsure of exactly what sources I was depending on. But, I am not the self-doubting sort, so did not back down. I was asked to provide sources for my comment.

As with all things climate — facts depend on one’s epistemological values.

This is what I was able to report to the instructors:

Have I mentioned that almost everything about Science topics is complicated and often complex as well?

Antarctic Ice Mass is an example.

When I said Antarctic Ice Mass has been increasing since the turn of the century, I was quoting a recent NASA reported on this NASA website page:

The study was published in 2015. Real science is always of the past, and studies like these can take years to do right, thus they seem “old” but are in fact often the latest studies available.

The study [ link to original Zwally study ], was reported byNASA here and quotes the study lead author, Jay Zwally, as saying:

“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” Zwally said. “But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for.”

The NASA article about the study [repeating the link] says: “NASA Study: Mass Gains of Antarctic Ice Sheet Greater than Losses”

“According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed   to [a gain of] 82 billion tons of ice per year between 2003 and 2008.”

Now, here’s the rub, as they say.  When one looks at NASA’s Vital Signs web page we are treated to this rather depressing graph of Antarctic Ice Mass losses:

The 2015 Zwally study — “the new analysis of satellite data, the Antarctic ice sheet” — shows precisely the opposite, GAINS  in the re-analysis by Zwally and his team instead of the DECLINES shown in the Vital Signs graphic above.

Sorting out these kinds of basic data conflicts takes literally weeks of journalistic research effort.  I have not  tackled this issue as of yet — but have been aware of the conflicting information — all from NASA — for several years.

It is not really  possible that both sets of information are true and correct.

I certainly don’t know.  But because NASA publishes contrary data, educators should not be making definitive statements about Antarctic Ice Mass, but rather should clearly say “Some NASA studies show Antarctica losing Ice Mass and some NASA studies show it gaining Ice Mass.”

I whipped up this alternate graph to show both sets of data on the same graph — GRACE from NASA Vital Signs and the gains found by Zwally et al. (2015):

The graph above uses GRACE’s 2002 zero as a common point — with Zwally’s 1992-2002 data to its left and 2002-2015 to the right.

I am aware that Zwally (2015) was sharply contested by the usual ice mass consensus team — but never required correction. Zwally is currently listed as being with the Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD and the Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD.

Zwally and his team have come back in 2021 with this peer-reviewed study:

Mass balance of the Antarctic ice sheet 1992–2016: reconciling results from GRACE
gravimetry with ICESat, ERS1/2 and Envisat altimetry H. Jay Zwally et al.
 29 March 2021 Cambridge University Press

Their latest analysis looks like this:

One sees the seasonal variation clearly at this scale. Although this latest analysis shows a tiny -12 Gt annual loss, I doubt that it is significant given what must be a fairly large +/- 1 SD (had it been shown). Even if the -12 Gt per year was physical and lasted all 9 years from 2012, the cumulative total nine year loss would be only 108 GT, a far cry from the NASA Vital Signs GRACE image’s minus 151 Gt per year offered to the general public as a sign of disastrous climate change.

I would appreciate any and all Ice Mass aficionados weighing in on the source of the disconnect between these two NASA approved Ice Mass calculations.

UPDATE: Reader John MacDonald pointed out that “One data item missing is the total ice mass of Antarctic.” The best guess total ice mass in Gt from the Wiki is 26.5 million Gt.

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via Watts Up With That?

October 6, 2021