ALONG ANTARCTICA鈥橲 west coast near the Amundsen Sea, great white glaciers the size of U.S. states slowly slide into the ocean. In the early 鈥�80s, scientists dubbed it the continent鈥檚 鈥渨eak underbelly鈥� after learning that ice here 鈥� which helps hold back the entire West Antarctic Ice Sheet 鈥� is anchored below sea level.
If oceans warmed, this unfortunate topography could cause rapid and irreversible retreat. In decades past, glaciologists had assumed these ancient features advanced and retreated on epic time scales 鈥� not in human lifetimes.
Ever since, climatologists have been spellbound watching the rapid changes. We now
know that melting the whole
West Antarctic Ice Sheet could cause 15 feet of global sea level rise. And that鈥檚
galvanized the scientific community, leading to a new $50 million joint U.S.-U.K.
project to predict ice melt rates.
Meanwhile, Antarctica鈥檚 other glaciers have drawn far less attention, even though if East Antarctica melted, it would raise global sea levels by a whopping 174 feet. Thankfully, its glaciers sit largely above sea level, where they should be safe for hundreds or thousands of years 鈥� at least that鈥檚 been the traditional thinking. But a startling string of new evidence, gathered from field expeditions, as well as air-and space-based observations, has scientists questioning their assumptions.
鈥淓ast Antarctica is the sleeping giant,鈥� says Amelia Shevenell of the 黑料社区, who鈥檚 studied the continent up close eight times since 1995. 鈥淲e don鈥檛 really understand it.鈥�
Melting just one nearly France-sized glacier in East Antarctica, called Totten, would unleash almost as much sea level rise as melting the entire West Antarctic Ice Sheet. Satellite data already show Totten Glacier is melting faster than any other in East Antarctica. And a recent study hinted at why: Far more of the glacier floats on warming ocean water than scientists thought.
To find out more, Shevenell and a large interdisciplinary team sailed as close as they could to the glacier鈥檚 mouth 鈥� a coastline where sea ice freezes against grounded icebergs. The captain had to turn around their vessel after nearly freezing into the ice. But they still managed to deploy a suite of scientific instruments to probe the region鈥檚 past.
One goal was to study sediment layers below the seafloor. By bouncing seismic signals off the sea bed beneath their ship, the team gained on a sort of 鈥淴-ray view.
They saw the bottom layers, which date date back more than 34 million years鈥� to a hotter Earth, before continental-scale ice sheets covered the region. Then, higher up in the sediment, pebbles marked the arrival of debris-toting icebergs. These kinds of sediment changes revealed glaciers retreating and advancing on 11 separate occasions.
Their results hint at ice melt when Earth鈥檚 temperatures and carbon dioxide levels resembled predictions for the not-too-distant future.
And the group spotted something else, too: Massive channels scar the seafloor. Sean Gulick of the University of Texas, Shevenell鈥檚 colleague, recalled seeing similar features off the coast of Alaska. These channels form when warm air melts surface ice and creates rivers of runoff that tunnel through the ice and carve the underlying rock en route to the ocean. That requires temperatures above freezing, a relative rarity across much of the southern continent.
鈥淭hat was completely unexpected,鈥� Shevenell says.
Their finding comes as scientists notice more surface melt across Antarctica. Last year, two Nature studies showed it鈥檚 more common than suspected. By sifting through decades of aerial and satellite photos, a team from Columbia University鈥檚 Lamont-Doherty Earth Observatory discovered some 700 drainage systems across the continent. They range from streams and ponds to 400-foot-wide waterfalls.
Shevenell suspects Totten got a one-two punch 鈥� warm ocean lapped at its underside as hot air melted the surface. But she can鈥檛 be sure without more data. So her team is working on a project to return to the glacier and drill down into the scarred sediments to more precisely date the glacier鈥檚 moves. They鈥檒l better unravel when Totten retreated and advanced, and why it鈥檚 so sensitive to climate change. But the project won鈥檛 be easy. The logistics of working in this environment could require drilling technologies not yet invented.
For their team, the risk and expense are well worth it to uncover secrets from an overlooked part of the continent. 鈥淚 think it is a complete oversight, and we鈥檝e been saying this for years,鈥� Shevenell says. Now that鈥檚 finally starting to change.
Betz, Eric (2018, September). The Sleeping Giant. DISCOVER MAGAZINE, 10-11.