Antarctica’s massive lakes, rivers, and streams could help us understand rising sea levels

Antarctica isn’t a huge, static block of ice where very little goes on. For the first time, scientists are getting a sense of just how active the continent’s extensive network of lakes, rivers, and streams is. These bodies of water have existed for decades on Antarctica, and their meltwater affects the stability of the ice shelf underneath. That, in turn, has important implications for sea level rise.

Antarctica’s landmass is surrounded by hundreds of floating ice shelves that play a key role in preventing sea levels from engulfing our coastal cities. In fact, these ice shelves keep the ground-based ice from flowing into the sea, which would raise sea levels by several feet. Scientists have long known that, in the summer, some surface ice and snow on these ice shelves melts, pooling in lakes and streams. But until now, the phenomenon was thought to be pretty rare, according to Alison Banwell at the University of Cambridge’s Scott Polar Research Institute, who wrote a comment on the new research.

Today’s study, published in Nature, shows that the network of lakes and streams is actually widespread on top of many ice shelves, transporting water for up to 75 miles. Some ponds were found to be up to 50 miles long. “The fact that there are these huge rivers moving water for hundreds of kilometers, that’s even quite an exciting discovery,” lead study author Jonathan Kingslake, a glaciologist at Columbia University’s Lamont-Doherty Earth Observatory, tells The Verge. “They’re very common across the ice sheet, but we are a long way from being able to understand how they behave and how they will impact the ice sheet in the long term.”

In fact, there’s a lot we don’t know about the way this meltwater interacts with the ice sheet. Lakes and ponds that form on top of the ice are thought to be dangerous. That’s because the weight of the liquid water can crack the ice; when water drains through the crevasses, it may freeze and expand, widening the cracks and fracturing the ice. This process is believed to have caused the break-up of the Larsen B Ice Shelf in 2002.

But the meltwater doesn’t only collect in puddles. Today’s study shows that it also flows downhill in rivers — for miles across the continent. And another study published today, also in Nature, shows that the meltwater doesn’t necessarily weaken the ice shelf beneath. This second paper analyzed a particular region called the Nansen Ice Shelf located in West Antarctica. Here, large and complex river networks allow huge amounts of meltwater to flow off the shelf into the ocean, with a 400-foot-wide waterfall. The drainage system may be protecting the ice shelf by getting the water off the ice quickly, before its weight cracks the ice.

Each red ‘X’ represents a separate drainage. Up to now, such features were thought to exist mainly on the far northerly Antarctic Peninsula (upper left). Their widespread presence signals that the ice may be more vulnerable to melting than previously thought.
Adapted from Kingslake et al., Nature 2017

That means the meltwater isn’t necessarily dangerous. “The meltwater acts as a jackhammer on an ice shelf is what we’ve always thought,” the lead author of the second Nature paper, Robin Bell, a polar scientist at Columbia University’s Lamont-Doherty Earth Observatory, tells The Verge. “This study suggests that we can’t just assume that if we turn up the temperature, every ice shelf will collapse.” Rather, the study suggests the process will be more complex.

Scientists expect that as temperatures warm up, we’re going to see even more meltwater in Antarctica. So understanding how this water behaves and what effects it has is key for predicting what’s going to happen in this part of the world, and whether or not it’s going to affect sea level rise.

In the first study, researchers analyzed satellite images from 1973 onwards, as well as aerial photos taken from 1947 onward. They found that a widespread and complicated drainage system made of lakes and rivers has existed across Antarctica for decades. Some of these streams and ponds are present as close as 375 miles from the South Pole, and at 4,300 feet above sea level. Those are areas that were thought to be clear of liquid water.

Whether the amount of meltwater has actually increased in the past 70 years is impossible to tell, says Kingslake. That’s because in the past, photos of the continent were not taken as frequently as today. So you might have a photo taken in 1973, and then another one taken in 1980, with no images in between, Kingslake says. That seven-year gap doesn’t allow researchers to understand long-term trends, and calculate whether we’re seeing more meltwater.

Massive summer melting on East Antarctica’s Amery Ice Shelf, seen from NASA’s Landsat 4 satellite. The image shows about 520 square miles.

“At the moment, the initial indication is that things haven’t changed significantly,” Kingslake says. But as the planet warms up, scientists are expecting to see more ice and snow from the surface to melt and puddle up in lakes or flow in rivers. What effects this liquid water will have on the stability of the ice shelf, however, remains to be seen.

“It is complicated and there are a whole bunch of processes that are really interesting and we don’t really understand,” Kingslake says. That’s why the Nature studies published today are important: they add a piece of the puzzle to figuring out how one of the largest reserve of ice on Earth works. As temperatures climb up and waters warm, all this information will be key to understand how sea levels will rise.

As for how Kingslake got interested in studying Antarctica’s drainage systems, it’s all thanks to Google Earth. In 2010, he used to spend lots of time surfing the site, he says. At one point, he noticed lots of ponds on Antarctica’s ice surface. That inspired him to study more detailed satellite images and look into the widespread system of lakes and rivers dotting the continent.

Today, Kingslake tells his students to never feel bad if they’re procrastinating by looking at Google Earth images. You never know what you’re going to find. “It’s not a waste of time!” he says.


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