You might not think about Antarctica very often. After all, there's not much there of immediate interest to human life — mostly just more ice than you could ever dream of. When we talk about climate change, we most often focus our attention up north on the Arctic, closer to more human settlements, and where all the cute polar bears and narwhals live. But the fact is, Antarctica's vast ice sheets and even larger expanses of annual sea ice coverage serve the planet by absorbing unbelievable amounts of heat. Without them ... well, nobody knows what would happen without them.
Because Antarctica is so vast and remote, and because the behavior of the ice sheet is so unpredictable and complex, Antarctica is tough to study. But researchers are pretty sure it's not normal when a 225-square-mile (583-square-kilometer) chunk of glacier breaks off into the ocean, which is exactly what happened in August of 2015. The resulting iceberg is about the same size as the Pacific island Guam, or the popular Spanish resort island Ibiza.
In studying this humongous calving event of the Pine Island Glacier, one of the two glaciers bordering the West Antarctic Ice Shelf, researchers from Ohio State University used new imaging software to examine satellite pictures taken of West Antarctica prior to the rupture. They found that over the course of a couple of years, a rift in the ice at the base of the West Antarctic ice shelf broke open — from the inside out.
What is troubling about the calving of the Pine Island Glacier is that the rift originated from the center of ice shelf 20 miles (32.2 kilometers) inland, which means that something is weakening it from the inside and underneath — most likely the warming of the ocean and the undersea rock supporting the shelf. This runs counter to the more common way rifts occur, which is at the edge where ice usually is thinnest. The team published its findings in the journal Geophysical Research Letters this month.
"It's generally accepted that it's no longer a question of whether the West Antarctic Ice Sheet will melt, it's a question of when," said study leader Ian Howat, associate professor of earth sciences at Ohio State, in a press release. "This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes."
Like, maybe in the next 100 years. This event would raise sea levels by as many as 10 feet (3 meters), which would flood some major cities around the world, including New York and Miami.
Another clue about the puzzling, troubling nature of this recent rift comes from the fact that it opened up in a deep spot in the ice — the bottom of a valley. These valleys form because Antarctica is basically a series of islands covered in and connected by massive amounts of ice. In the places between the land, the ice has the potential to come in direct contact with warmer, saltier seawater that promotes melting. Researchers haven't known whether the seawater was intruding so far into Antarctica's interior, but this rift seems to confirm these suspicions.
"We need to understand exactly how these valleys and rifts form, and what they mean for ice shelf stability," said Howat. "We're limited in what information we can get from space, so this will mean targeting air and field campaigns to collect more detailed observations. The U.S. and the U.K. are partnering on a large field science program targeted at that area of Antarctica, so this will provide another piece to the puzzle."