Is Antarctica gaining or losing ice?

Question

A recent NASA study says Antarctica is gaining ice:

Ice, Cloud and land Elevation Satellite (ICESat) data (2003–08) show mass gains from snow accumulation exceeded discharge losses by 82 ± 25 Gt a^–1, reducing global sea-level rise by 0.23 mm a^–1. European Remote-sensing Satellite (ERS) data (1992–2001) give a similar gain of 112 ± 61 Gt a^–1.

This finding was reported in numerous media sites such as CNN, New Republic and USA Today.

This finding contradicts numerous prior scientific claims such the U.N.’s Intergovernmental Panel on Climate Change:

Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass,

and a 2014 study published in Geophysical Research Letters.

However, the average rate of ice thinning in West Antarctica has also continued to rise, and mass losses from this sector are now 31% greater than over the period 2005–2010.

So is Antarctica losing ice or gaining ice?

Answer 1

UPDATE: I wrote this answer in 2015, and it was accepted as the best answer. Since then, new information is available which provides a better answer. I have up voted DavePhD's answer and hope others will as well.

ORIGINAL: At this point, the only accurate answer is that we don't know for sure. This study indicates that Antarctic ice is increasing overall, while many other studies indicate that it is decreasing. This study used data only from 1992 to 2008, while other papers using more recent have reached the opposite conclusion. Even this study indicates that the rate of ice gain is slowing, and will become a net loss in the future.

Robert McSweeny has written a good summary of the recent article, with some comparisons to other studies. The study was done using satellite-based lasers to measure ice thickness over different regions in Antarctica, from 1992 to 2008. The study found that the Antarctic Peninsula and West Antarctic Ice Sheet (WAIS) both lost ice during that time, and the East Arctic Ice Sheet (EAIS) accumulated on average about 1 cm of ice. Overall, the study found that there was a net increase of ice.

The study concludes that the gains in ice over East Antarctica outweigh the losses on WAIS and the peninsula between 1992 and 2008.

According to the study, Antarctica has been gaining ice for about 10,000 years:

So, where is this extra ice on East Antarctica coming from? The researchers say it all started around 10,000 years ago, at the end of the last Ice Age. As the air warmed up, it could hold more moisture, and the amount of snow that fell onto the ice sheet doubled. Since then, this extra snow has gradually been compacting into ice, making the ice sheet thicker.

But the study also measured a reduction the overall Antarctic ice gain, i.e. ice losses in other parts of Antarctica are catching up with ice gains in the EAIS:

But the gap between ice gained and ice lost is getting smaller. Between 1992 and 2001, the net gain was 112bn tonnes a year, the paper finds. This dropped to 82bn tonnes between 2003 and 2008.

Several other studies have measured net ice losses in the EIAS in years more recent than were included in this study, for example:

Some of the more recent studies use the CryoSat-2 satellite, which was launched in 2010. A paper published in July analysed the first three years of this data, and finds that between 2010 and 2013, West Antarctica, East Antarctica, and the Antarctic Peninsula lost 134bn, 3bn, and 23bn tonnes of ice per year, respectively.

In summary, this is one of many studies on the subject, and more work will be needed to fully answer the question. It does not, however, contradict any of the key findings of climate science.

It will take a number of other studies, both satellite and on-the-ground research, to confirm if the new NASA study is correct about East Antarctica. If it is confirmed, it will still only apply up to 2008, not to the present day.

As Prof. Richard Alley states:

What is absolutely obvious is that this does not in any way mean that we don’t need to worry about sea level rise from our warming.

Answer 2

Antarctica is losing ice.

The 13 June 2018 article Mass balance of the Antarctic Ice Sheet from 1992 to 2017 Nature volume 558, pages 219–222 (2018) analyzed data from three techniques, altitude measurements, gravity measurements, and input-output estimates.

it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017

...

Across the full 25-year survey, the average rate of mass balance of the AIS [Antarctic Ice Sheet] was −109 ± 56 Gt yr⁻¹

Concerning the information in the OP finding gain, the 2018 article says (with reference "74" being the first OP study):

With a few exceptions, rates of mass change determined from radar and laser altimetry tend to differ by less than 100 Gt yr⁻¹ at all times in each ice-sheet region (Extended Data Fig. 5). The main exceptions are in the EAIS, where one estimate ⁷⁴ reports mass trends that are roughly 100 Gt yr⁻¹ more positive than all others during the ERS and ICESat periods, and in the WAIS, where two estimates ^71,74 report rates that are about 70 Gt yr⁻¹ less negative than the others during the ICESat period. Among the remaining datasets, the closest agreement occurs at the APIS, where mass trends agree to within 30 Gt yr⁻¹ at all times; the poorest agreement occurs at the EAIS, where mass trends depart by up to 100 Gt yr⁻¹. The largest differences are between datasets that are constant in time during periods where rapid changes in mass balance occur in the annually resolved time series, suggesting that a proportion of the difference is due to their poor temporal resolution. Mass-balance solutions from the relatively short (six-year) ICESat mission also appear to show larger spreads compared to those determined from longer (decade-scale) radar-altimetry missions. This larger spread is due in part to differences in the bias-correction models applied to ICESat data ^74,76,77,78 and in part to the large influence of firn densification on altimetry measurements over short periods, which have been corrected for using different models. Firn-densification models are generally not applied to mass-balance solutions determined from radar altimetry. Further analysis of the corrections for bias between ICESat campaigns and firn compaction is required to establish the statistical significance of the differences and to reduce their collective uncertainty. Comparing rates of mass change (Extended Data Table 3), the average standard deviation of all mass trends at each epoch over the common period 2005–2015 is less than 54 Gt yr⁻¹ in all four ice-sheet regions. The largest spread between the individual values occurs in the EAIS. Other than this sector, the individual estimates lie close to the ensemble average, considering the respective uncertainty of the measurements.