|May 06, 2020|
Antarctica: Too big to melt
|"What happens in Antarctica affects us all," says Ella Gilbert, a climate scientist with the British Antarctic Survey.|
But does everyone know what's happening in Antarctica, let alone understand how events there could threaten communities around the world?
Some people may have gotten a hint during a brief few days in February, when international headlines reported record heat baking the Antarctic Peninsula at the height of the southern hemisphere's summer. It was a rare moment in which our southernmost continent made worldwide news.
But the broader story --- one that's since been eclipsed by coverage of the COVID-19 pandemic --- gained much less attention. February's heat, it turns out, was just one in a string of climate-related developments on the continent that could affect the whole planet.
As the COVID-19 pandemic shows, early dissemination of science-based information saves lives during a crisis. Scientists have long warned that the same is true of the unfolding climate emergency: If people receive --- and believe --- evidence that burning fossil fuels threatens the climate, we can come together to flatten the arc of rising temperatures and protect vulnerable populations, including low-lying coastal communities.
That's particularly relevant when it comes to warming in Antarctica, where 90% of the planet's glacial ice holds the key to stable sea levels across the globe. Scientists have expressed concerns about melting of the continent's ice for some time now: It's already raising sea levels and could dramatically flood global coastlines in the years ahead, potentially at a rapid rate.
But despite years of warnings, the question remains: Does the general public know enough about climate and the Antarctic to come together and reduce the threat?
Antarctica's Climate: A Complex, Intertwined System
The first hint of Antarctica's warm summer came in September 2019, when the sea ice surrounding the continent finished the austral winter well below the historic average, continuing a five-year trend.
Below-average sea ice in the Antarctic is not necessarily a direct factor of climate change --- some scientists attribute the decline over the past five years to natural variability, although questions remain about the additional influence of anthropogenic forces. But we do know that ice-free ocean waters absorb more heat during the long days of summer, and that the waters in the Antarctic Ocean have already been made warmer by greenhouse gas emissions.
And as ice retreats each year, it can further intensify the effects of climate change because it's no longer there to shield the water from the warming rays of the sun.
"Sea ice is very reflective," explains Claire Parkinson, a NASA senior scientist who has studied polar climate systems for more than four decades. "As it retreats the sun's radiation absorbs into the ocean, which helps warm the atmosphere."
Because of this, some scientists say low sea ice, whether from natural or human causes, may have magnified the startling Antarctic warmth that came later in the year.
A second factor affecting the complex systems in the region also became evident in September, when sudden stratospheric warming occurred 20 miles above Antarctica. Scientists also attributed this rare occurrence for the southern hemisphere to natural variation. However, as with low sea ice, it added heat to an already warmed Antarctic Ocean, and scientists believe this later helped fuel Australia's devastating wildfire season by disturbing on-the-ground weather systems.
As Parkinson explains, even "natural" warming events are now amplified by the impacts of human activities on the climate, including deforestation and carbon pollution. "Climate systems are very intertwined," she says.
Things got worse in November. As the austral summer approached, news of West Antarctica's dramatic melting of snow and ice trickled northward to the rest of the world. By December melt rates were estimated at a whopping 230% above average.
It was the beginning of a summer of widespread melting.
The Belgian scientists who first reported the development used climate models to estimate melt rates, but satellite images revealed direct effects of melting two months later. Analysis by scientists at NASA and the University of Colorado showed widespread pooling of meltwater on the surface of the George VI Ice Sheet in West Antarctica. Such pooling is a marker of rapid melting that is ordinarily more common in the comparatively warmer climates of Alaska and Greenland.
Alison Banwell, a glaciologist at the University of Colorado Boulder who studies Antarctic ice shelves, says the lakes were larger in size and number than anything seen over the past 20 years. "They were also present almost continuously from December to March," she says. "It's the longest duration we've seen in recent history."
Banwell, whose work ranges from analyzing satellite data to wading into Antarctic melt pools to install monitoring instruments, says early indications suggest the George VI region may have experienced the warmest air temperatures in two decades of observation, though she cautions that analysis is not yet complete.
According to Banwell the warmth appears consistent with human-caused climate change.
The next troubling sign came in January, when researchers found evidence of warming when they drilled a nearly 2,000-foot hole to the bottom of the Thwaites Glacier, one of West Antarctica's largest ice masses. Instruments lowered into the hole showed warm ocean water swirling underneath the ice, signaling melting at a critical part of the glacier. David Holland, a physical climate scientist from New York University associated with the research, wrote that it "suggests that [the Thwaites] may be undergoing an unstoppable retreat that has huge implications for global sea level rise."
The Thwaites, which is the size of Great Britain, has long been considered one of the world's most important glaciers in terms of global sea-level rise because it acts as a dam against the massive West Antarctica ice sheet. If melting destabilizes the Thwaites, as Holland says may be happening, ice from the massive ice sheet would pour into the ocean.
NASA scientists estimate this region has enough "vulnerable ice" to raise global sea levels by at least four feet.
A Warm Wind Blows, the Cracks Begin
News from the Thwaites Glacier was soon followed by the February "heatwave." The record-breaking temperatures, which scientists called "incredible and abnormal," occurred on February 6 and 9, when the air at two West Antarctica locations reached nearly 70 degrees Fahrenheit --- far above the more typical high of 50 degrees and all-time records for the entire continent. The overheated air helped melt an estimated 20% of the region's seasonal snow accumulation in just six days.
Gilbert, the climate scientist with the British Antarctic Survey, attributed the heat to a "perfect storm" of meteorological conditions, where high pressure over South America pushed warm air over the Antarctic Peninsula, creating optimal conditions for dry, warm "foehn winds" to roll down local mountains and produce rapid temperature increases.
But Gilbert, who wrote about the heat in Britain's Independent newspaper, says this occurred against a backdrop of ongoing Antarctic climate change.
"In the simplest sense," she tells us by email, "if you're starting from a warmer baseline, then any additional warming on top of that --- due to foehn winds, or any other phenomenon --- will push temperatures higher."
Additionally, evidence in recent years suggests global climate change is increasing both foehn winds and the influence that warm air over South America has on West Antarctica.
Just as the soaring temperatures attracted international attention, satellite imagery on February 9 showed a 300-square-kilometer iceberg break away from the Pine Island Glacier.
The glacier, like the nearby Thwaites, prevents the West Antarctic Ice Sheet from flowing into the ocean. It has been deteriorating for decades, but with increasing speed. The giant berg sheared off along cracks scientists first observed close to a year ago, which they attribute to warming oceans.
"Warmer ocean waters are pushed more strongly toward Antarctica," says Eric Rignot, professor of earth system science at the University of California, Irvine, who communicated by email. Rignot has studied Antarctic glaciers for 30 years and ties the warmer waters to changing wind patterns associated in part with a warming atmosphere.
From West to East
As if the news out of West Antarctica isn't concerning enough, evidence also points to accelerated melting in East Antarctica, home to the planet's largest bodies of glacial ice. Although temperatures there are still too cold to drive significant surface melting, scientists say warming ocean waters are eroding glaciers much like the Thwaites and Pine Island glaciers of West Antarctica.
In late March, as autumn fell on the southern hemisphere, new research added to concerns over East Antarctic ice. Analysis of satellite data found the region's Denman Glacier has retreated three miles in the past two decades. Researchers warned that the Denman's unique geography puts it at risk of widespread collapse, increasing concerns that Antarctic melting could spark rapid, global sea-level rise.
On its own the Denman has the potential to raise sea levels by five feet.
"We view the Wilkes Land sector with Denman and other glaciers as the biggest risk for the future," says Rignot, who participated in the research. He calls the current situation "the premise of a collapse" in that part of East Antarctica. But he says collapse there is not imminent.
"We do not know yet exactly how much time we have," he says of East Antarctica.
But the advanced state of melting in West Antarctica presents a clearer picture. He says if swift action is not taken on climate change in the next decade, "absolutely nothing will stop these glaciers" from further retreat that jeopardizes the West Antarctic Ice Sheet.
Out of Sight, Out of Mind?
Antarctica is the world's remotest continent, with a small and mostly seasonal human population limited to scientists and occasional tourists visiting by cruise boat. Especially amid a global pandemic, events there may seem disconnected from our lives.
But as Gilbert of the British Antarctic Survey explains, changes on the continent have far-reaching consequences for global sea-level rise, changing ocean currents, and even on the pace of climate change itself.
The news from the southern continent adds to a steady stream of warnings about the unfolding climate crisis. But while the current pandemic has sidelined climate concerns for many, it may also offer an opportunity to address the crisis. The $2 trillion stimulus package signed into law in late March demonstrates the availability of massive funding for emergency response. And lawmakers are already discussing a similar-sized bill to come this summer, with early signs that infrastructure may be a focus.
Some climate and renewable energy experts see it as an opportunity to speed U.S. transition to cleaner energy and build resilience into coastal communities vulnerable to sea-level rise.
Whether that occurs will depend on a later debate, and perhaps also on how well the climate news coming out of remote Antarctica and other locations stays in the forefront of the public consciousness.