The European Space Agency (ESA) released a video this past week showing the evolution of two very large and disconcerting cracks in Antarctica’s Pine Island Glacier. They have each grown to 20km in length and could shear off a hunk of ice the size of Paris and Manhattan combined.
The Pine Island Glacier—located at the base of the Antarctic Peninsula on the western side of the continent—has always shipped Antarctic ice out to sea at prolific levels, but it’s become famous in recent years due to its ever increasing output. These new cracks are just the latest development in a flurry of epic calving events at Pine Island. These used to occur about every six years but are now happening on an almost yearly basis.
The ESA compiled images of the cracks taken by one of their two polar orbiting Sentinel-1 satellites to make the video. Sentinel-1 is continuously monitoring land, sea, and sea ice conditions with a synthetic-aperture radar instrument that allows it to take pictures in all weather conditions and even at night—a key feature in high latitudes, which experience long periods of darkness in the winter months. These satellites are part of ESA’s larger Copernicus mission.
Pine Island Glacier feeds into a floating body of ice called an ice shelf. A recent study published in Science Advances this month revealed that these ice shelves, and Pine Island Glacier in particular, are experiencing accelerated melting from underneath, as a combination of fast moving and buoyant plumes of warm water carve troughs into their bottom surface. This makes the shelves more prone to large calving events and ultimately to shrinkage and retreat.
“Warm water circulation is attacking the undersides of these ice shelves at their most vulnerable points,” said lead earth scientist and lead author of the report, Karen Alley. “These effects matter,” she added. “But exactly how much, we don’t yet know. We need to.”
The large calving event building at Pine Island Glacier also comes at a period of particular concern for melting glaciers around the world. The International Panel on Climate Change released its special report on the state of the Earth’s cryosphere last month in which it predicted continued warming of ocean waters and increasing mass loss of the Antarctic Ice Sheets—of which Pine Island Glacier is a part—throughout the 21st century.
Climate change has long been known to be a stressor on glaciers the world over, but a recent study published in Nature Geoscience, reveals just how bad it’s been for those in the Andes: Glaciers in this South American mountain range have the unfortunate distinction of being both the fastest melting and the largest contributors to sea level rise in the world.
Glacial melt has been watched carefully for decades, but because of limitations in technology and methodologies, scientists haven’t gotten the most precise picture of how much melting is occurring, or how fast.
Previous techniques looked at regional locations scattered throughout the Andes like the Northern Patagonian Icefield and then extrapolated those findings. Others gave hazy estimates from low-resolution, remote-sensing images. But these methods can miss individual glaciers and clusters of just a few or more.
In an attempt to refine understanding of Andes-wide glacial melt, the researchers harnessed the image-collecting power of a satellite with the Asimovian name of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). ASTER has been taking high-resolution, stereoscopic images of the Andes since 2000. By compiling these images and integrating them into digital models, the study’s scientists were not only able to get a new ice loss estimate for the entire Andes, but also for individual regions and individual glaciers over the past two decades.
With this high resolution dataset, the researchers determined that the entire glacial range in the Andes shrunk about 23 gigatons (1 gigaton=1 billion tons) since 2000—more than previous studies have found—and account for 10 percent of global sea level rise. At this rate, some of these ancient glaciers will be gone in just over two centuries—but the rate is accelerating.
Digging through the data, the researchers also parsed out an array of differing melt rates between glaciers that revealed the areas of the heaviest melting: Patagonia (Chile, Argentina) and the tropical Andes (Colombia, Ecuador, Peru, and Bolivia). Previous research has shown that low altitude glaciers in some of these areas like Peru have lost as much as 50 percent of their mass since 1970.
“[Patagonia] is the region that contains the largest surface of ice, and [so] it’s normal to expect that the highest loss is going to be there,” lead author and glaciologist Inés Dussaillant told GlacierHub over the phone, adding that glaciers terminating in oceans and large lakes like those in Patagonia also experience heavy amounts of calving—which accounts for more than half of all the ice mass loss observed in the Andes. The glaciers in the tropics—mostly in Ecuador and Colombia—Dussaillant explained, are relatively small and highly sensitive to changes in climate. “A small change in temperature can make tropical glaciers lose a lot of mass,” she said.
Perhaps the most troubling of the team’s findings, however, dealt with glaciers’ contribution of freshwater to rivers through snow and ice melt. During the summer months, snow and ice melt from glaciers flows into streams and rivers, adding to the overall water availability of a particular region. This is particularly important in the Dry Andes of the northern and central regions of Chile and Argentina. Since 2010, these heavily populated semi-arid regions have been strapped in what climatologists have called a megadrought. The team found that increased glacial melting in these areas since 2009 actually helped to mitigate some of the most severe impacts of the drought. But as glaciers continue to shrink because of anthropogenic climate change, their ability to act as this natural salve is going to diminish or disappear.
“They are not going to be able to contribute to rivers eternally,” remarked Dussaillant. “There will be a moment where they’ll no longer be able to contribute during these periods of drought.”
This point highlights the larger implications of the study, which is that millions of people live near, and depend upon, these glaciers in the Andes, and the drastic reduction or total disappearance of them is going to have potentially severe consequences. Dussaillant, who is Chilean, pointed out that more than half of the population of Chile lives in or near the capital city Santiago, which lies in this region.
Eyal Levy, an industrial engineer and Andean climber who is also from Chile, told GlacierHub that Chileans are “starting to become very worried about the water stress. He added that rural areas and poorer communes around Santiago have been “seriously impacted.”
Glaciers are a conspicuous part of the everyday scenery, Levy said, and their shrinking takes a toll on people’s emotions. “People talk about melting glaciers with sadness, worry, and without knowing what to do,” he said.
Dussaillant hopes that the high resolution dataset gathered from this study will be used by other glaciologists for local or regional studies. “I study glaciers because they tell us what is happening,” she said. “It’s showing us that climate is changing, and the climate is a global thing. So what’s happening in the Andes … it concerns us all.”