Many of the scientific studies published in the past two years on the stability of the Antarctic ice sheet can best be characterized as anxiety-inducing, if not outright panic-causing.

Studies have shown that huge chunks of the continent may be far more unstable than previously thought, and more susceptible to melting from manmade climate change and other factors. This is especially the case with the West Antarctic Ice Sheet and the glaciers along the Antarctic Peninsula.

See also: Paris Climate Summit may get world at least halfway toward global warming target

However, last week a study was published that seemed to offer up a bit of much-needed good news. In the Journal of Glaciology, a group of NASA researchers led by Jay Zwally of NASA's Goddard Space Flight Center in Maryland, reported that satellite data shows that as a whole, Antarctica has been gaining, rather than losing mass during the past two or more decades.

Much of West Antarctica lies below sea level, raising concerns about glacier destabilization.

The mass gains, according to the study, are mainly from increased snowfall in the continent's interior, particularly across the East Antarctic Ice Sheet, and they are just barely more than enough to offset the sea level rise impacts from the melting occurring in the West Antarctic and Antarctic Peninsula.

“The main point is that Antarctica is now gaining mass by about 100 gigatons per year, and the previous reports… had a mass loss of 70 to 100 gigatons,” Zwally told Mashable in an interview.

Antarctica is overall accumulating ice, but parts have increased ice loss in last decades: https://t.co/j7x9idUdM8 pic.twitter.com/VMNbV1LB3m — NASA (@NASA) October 30, 2015

These results were trumpeted by many media outlets as a drastic reversal of NASA scientists' previous research, which relied on other satellite systems and observational data, that showed the continent as a whole or in part to be shedding ice at an increasing rate.

However, even Zwally said the study does not contradict the troubling trends seen in western Antarctica, where the Thwaites and Pine Island glaciers have been speeding up what may be an irreversible slide into the Southern Ocean. This slide could even occur in our lifetime.

Zwally also said his work is not exactly a reversal of previous studies.

“It’s an advancement of knowledge, it’s not really a reversal, it is a reversal in the sense that it went from negative to positive overall,” he said, referring to the continent's mass balance.

Troubling findings for small island nations, coastal cities

As if to smack the optimism down as quickly as possible, another study, this one published in the journal Proceedings of the National Academy of Sciences on Monday and based on both observations and computer modeling, falls squarely in the "Oh my, what have we done!?" camp of Antarctic research.

The study, from two researchers at the Potsdam Institute for Climate Impact Research in Germany, shows that if the erosion of the ice shelves in West Antarctica continue at current rates, it may inexorably lead to the complete destabilization of the Amundsen Sea sector of ice.

This would set in motion a global average sea level rise of about 3 meters, or nearly 10 feet, possibly as soon as this century.

Comparatively, the current high-end projection for sea level rise through the year 2100, from the U.N. Intergovernmental Panel on Climate Change, is about 1 meter, or 3.3 feet.

Velocity changes in the past decade for West Antarctic outlet glaciers. Red colors indicate a speeding up of a glacier's movement into the sea. Image: NASA

This would cause more than enough sea level rise to permanently inundate small island nations, like Kiribati and the Solomon Islands, and threaten some of the world's largest cities, like New York, Shanghai and Dhaka.

The outlet glaciers in this region, such as the Thwaites and Pine Island glaciers and their tributaries, are flowing faster into the sea as insidious forces erode their floating ice shelves from above (warming air temperatures), and below (warming ocean currents).

As this happens, the floating ice shelves, the doorstops that had been holding back huge amounts of ice from miles inland, are weakened and removed, freeing up ice from far inland to begin sliding downhill.

The study states:

"The currently observed retreat in West Antarctica hence might mark the beginning of a millennial period of self-sustained ice discharge from West Antarctica and require long-term global adaptation of coastal protection, such as the building or rebuilding or raising of dykes, the construction of seawalls, or the realization of land fills in the hinterland."

Zwally likened Antarctica to a bucket of water that is leaking out of the bottom, while there is also a hose connected to the top that is adding water. According to his data, there is more water being added via the hose than is being lost at from the bottom.

He says that, if his group's data is correct, the ice melt in the West Antarctic may eventually catch up to the thickening influence from the increased snowfall, within about 20 to 30 years from now.

“Overall, I have tried to make the point that this should not be, our results... should not induce complacency with respect to climate change,” he said.

“The climate is warming dramatically, it’s due to greenhouse gases, we need to do something about it, and the climate deniers should not take comfort in this result which is one of the many things happening globally and it doesn’t mean that climate change is not taking place,” he said.

Zwally said he differs with other researchers on the direness of the melt rate of West Antarctic outlet glaciers (the glaciers that terminate in the sea), pointing out that scientists don't have a thorough understanding of when the glaciers began retreating.

Other scientists disagree with Zwally's study

Tom Wagner, a NASA climate scientist who was not involved in either of the two new studies, said Zwally's study is an example of how the scientific community works to advance knowledge.

“A normal part of the research is somebody says one thing, somebody says, "ah maybe not so much," that’s the healthy process that we have,” Wagner said in an interview.

Velocity of glaciers in the West Antarctic Ice Sheet. Image: NASA

But the bottom line, Wagner said, is that "... We’re losing tremendous amount of ice around the world… we’re even losing tremendous amounts of ice from around Antarctica.”

“What this study shows is that East Antarctica may be gaining ice,” Wagner said.

“It doesn’t change the overall picture that the planet is warming up, we’re losing ice and sea levels are rising.”

Wagner said people should not lose sight of the recent scientific realization that many West Antarctic glaciers are seeing "crazy retreat" rates.

"The question for us though is how fast is that retreat going to cause sea levels to rise.” He said scientists get nervous when they look into the distant past, back to around 20,000 years ago, since there is evidence for 10 feet of sea level rise in just one century.

If that were to occur during the next 100 years, as the new study suggests it could, it would reshape the global map and severely challenge many nations' ability to adapt.

Ian Joughin, a coauthor of some of the recent studies on the instability of the West Antarctic Ice Sheet, said that the East Antarctic Ice Sheet could be gaining mass, as Zwally contends, but that possible measurement errors relating to the degradation of satellite sensors used in the study might make this an artifact rather than a real trend.

"By in large, other measurements, some relying on the same satellites, suggest no loss or a small positive imbalance in East Antarctica, which is substantially smaller than the strongly negative imbalance in West Antarctica (net loss overall)," Joughin, a researcher at the University of Washington's Polar Science Center, told Mashable in an email.

"This cannot be construed as the community reversing itself because Jay has been arguing this point for a long time, and the majority of the community has disagreed," he wrote.

"This is the way science works (i.e., there are still those challenging evolution after more than a century, but nobody is saying this means the community has reversed itself on evolution.)"

In an email conversation with Mashable, several other researchers who specialize in ice sheet dynamics agreed with Joughin's points regarding the potential data errors.

Zwally defended his work, saying he and his colleagues checked the data they used against available weather observations and computer modeling.

“This requires a high level of accuracy and we have worked on that to get the best accuracy.”