The past two weeks have brought one disturbing story after another about the future of the largest ice sheet on the planet — the vast frozen expanse of the Antarctic continent. Once viewed as a stable area of ice at least two miles thick in some places, recent research makes Antarctica seem more like a ticking sea-level-rise time bomb that is counting down more rapidly than ever before.
So, how worried should you be about these findings, and what do they mean for the present day and near-term future, which, let's face it, most of us care much more about than hardships that might not occur until the year 2100 or beyond? Mashable reached out to several top climate scientists, including co-authors of the newest findings, to help put the news into perspective.
First, here's a brief recap of the three major studies that were recently published.
On May 12, two studies were released that sounded the alarm about the instability of parts of the Antarctic ice sheet. One of the studies found that the "collapse" of parts of the West Antarctic Ice Sheet is now likely inevitable, and that this will play out over the course of the next 200 to 1,000 years. The study, by Ian Joughin of the University of Washington and several colleagues, had a key caveat, though. This exception was missing in many media reports: it did not consider a worst-case melting scenario, and stated that the biggest uncertainties don't concern the inevitability of the collapse, but rather the timing.
In other words, it could come sooner than 200 years. The study found that, based on recent ice loss rates and the movement of the Thwaites Glacier in West Antarctica, as well as computer model projections, "early-stage collapse has begun."
The glaciers of West Antarctica are already responsible for the majority of the Antarctic continent's contribution to global sea level rise, and if these glaciers were to completely collapse, sea levels could rise by at least four feet, potentially inundating coastal cities around the world. Far greater sea level rise — possibly up to 15 feet — would result if other parts of the West Antarctic Ice Sheet were to destabilize as well.
The other study released on the same day examined the retreat in the grounding lines of several West Antarctic Ice Sheet glaciers between 1992 and 2011. It found that as West Antarctic glaciers have become more unstable, their grounding lines, which is where the ice meets the ocean and becomes floating ice, have deepened, which provides warm ocean waters with easier access to the ice's underbelly.
In addition, the study showed that ice loss rates have not only sped up at the grounding lines, but also more than 100 miles inland, compromising the entire ice sheet that the glacier helps hold back from the sea. The data showed that there is no high ground, or hills, underneath the upstream areas of the glaciers that could slow or stop the flow of these glaciers into the sea.
Then, on May 19, another study that took advantage of new and comprehensive satellite imagery of 96% of Antarctica was released. This work showed that the rate of ice loss in Antarctica has doubled since 2010, when compared to the period from 2005 to 2010.
From these three studies we now know a few main points:
- First, the West Antarctic Ice Sheet is already losing ice at an accelerated rate, and is likely to continue to do so for hundreds of years.
- Second, the complete collapse of the entire West Antarctic Ice Sheet is not guaranteed, but it is quite plausible.
- And third and most importantly, continued global warming due to manmade emissions of greenhouse gases will help determine how much sea level rise we will see from Antarctica and Greenland.
The use of the term "collapse," which connotes an imminent calamity, rather than a long, relatively slow process (glaciers melting at, literally, a glacial pace) generated quite a bit of chatter in the climate journalism community, but in interviews, scientists defended the word as apt for this situation.
"Indeed, it is possible that the [word] 'collapse' brings the wrong thought to some people. On the other hand, it is clear that Joughin et al. did not simulate the worst case, so care is required in more than one direction," Richard Alley, one of the foremost experts on the fate of the world's ice sheets, said in an email conversation. Alley was not involved in the new research on the West Antarctic Ice Sheet.
"The uncertainties in sea-level rise projections have always been strongly on the 'bad' side — there is a central or best estimate, and the rise might be a little less than that, or a little more, or a lot more," Alley said. "Over the last couple of decades, the sea-level rise from the ice sheets has been about 0.6 mm/yr, from a reservoir of more than 60 meters, which is about the same as me going on a diet and losing 1/3 of one potato chip over a year.Obviously, if I were serious about dieting, I could lose weight much faster than that. We are rather confident that too much warming will cause ice-sheet shrinkage, and the possibility that the ice sheets will diet seriously has been weighing on us for a long time."
How is sea level rise, including from melting Antarctic ice, already affecting us?
Sea level rise is not just a concern for the future, it is already heightening coastal flood risks worldwide. For example, because the sea level in the New York City area rose by about a foot between 1900 and 2012, when Hurricane Sandy struck, about 80,000 more people were affected by flooding in New York and New Jersey than would have been without that increase.
Sea level rise is already escalating the risk of severe coastal flooding in states like Florida, Virginia and New York, and is expected to ratchet up flooding risks in the coming years.
Research by Climate Central, a nonprofit climate science and journalism organization, found that $71 billion of Florida property sits on land less than two feet above the high tide line. "Within less than the term of a 30-year mortgage, sea level rise could cause floods this high to occur once every five years, or even every year, depending on the location," a Climate Central report found.
The Thwaites Glacier alone is contributing about 10% to the current globally averaged rate of sea level rise, which is about 0.13 inches per year, Joughin says. That may sound minimal, but added up over the course of a century, that would yield one foot of sea level rise. Because of expected increases in the loss of land-based glaciers in Greenland, Antarctica and other areas, Joughin says the end-of-century figure may be closer to three feet.
"It shouldn't be forgotten that real problems are happening to real people now," as a result of sea level rise and coastal storms, Joughin says.
Do these findings mean New York, Singapore, and Dhaka will be underwater during the next 50 years?
No, but they do mean that these cities, and other coastal locations, need to prepare for increased impacts from the combination of sea level rise and the surge associated with coastal storms.
Sea level rise is gradual, but over the long term the effects add upSea level rise is gradual, but over the long term the effects add up," says Joughin. Nobody is going to wake up and find themselves suddenly flooded. That said, rising seas do increase the likelihood of storm surges reaching farther inland. And if you happen to live in Bangladesh or other low lying regions, even the current rate [of sea level rise] is important."
Are we totally screwed already, making it pointless to try to cut emissions, since the collapse of this region of the ice sheet is viewed as inevitable? What could emissions cuts do to lessen the severity of Antarctic ice melt and sea level rise?
The studies on the collapse of parts of the West Antarctic Ice Sheet actually reinforce the need to address the emissions of greenhouse gases, such as carbon dioxide, that are helping to increase global temperatures.
We've already destabilized part of Antarctica, the studies showed, but we have a choice about what else we want to set into motion.We've already destabilized part of Antarctica, the studies showed, but we have a choice about what else we want to set into motion.
The decisions made now and during the next few decades will determine how much more of the ice sheet we destabilize, and how quickly.
Here's how Eric Rignot, a senior research scientist at NASA and co-author of one of the new studies, thinks about the energy options before us.
"Sustained climate warming will not make things any better in Antarctica," he told Mashable. "It is difficult to say, but broadly speaking, by slashing emissions now we will avoid hitting major surprises down the line, and extreme scenarios of rapid change which we have no idea about."
When it comes to melting glaciers, no one likes a surprise party.