Robert Fletcher / AP

The first-ever survey of melting water on the entire continent of Antarctica has revealed an extensive network of about 700 lakes and streams on top of ice shelves. A second study published in the journal Nature described a river draining meltwater, mitigating the risk of the moving water collapsing the ice into the ocean.

The big questions: How much can the rivers buffer the effects of warming and prevent the ice shelves from collapsing? Or will the Antarctic rivers carve to the bottom of the continent and move melting ice into the ocean like what is happening in Greenland?

Why it matters: Scientists knew rising seawater temperatures were melting the underside of ice shelves. But they hadn't been considering what was happening on the surface because they didn't know the extent of the water there. The discovery will affect models of global sea level rise in response to climate change.

Robin Bell from Columbia University:

"We used to assume that if the temperature increased, ice shelves melted and sea level went up. But it is more complex. Water flows and moves. We don't know the impact of that."

Two concerns:

  1. As these streams and rivers move across the top of ice shelves, they weaken them and increase the risk of the ice collapsing into the ocean. By one estimate, the entire Antarctic ice shelf contains enough ice to raise global sea levels by 60 meters.
  2. Most of the moving water originates at higher elevations where more of the sun's light is absorbed by rock and blue ice, increasing the rate of ice melting. That could mean more water moving across the surface of the ice.

Methodology: Jonny Kingslake at Columbia University reviewed historical aerial photographs and satellite imagery and found a vast network of rivers and lakes has existed on the continent for at least 70 years. Robin Bell, an author of the second study, analyzed satellite and airborne imagery and found that in six out of eight melting seasons between 2006 and 2015, a 130-meter-wide river drained an entire lake on top of the Nansen Ice Shelf in one week, before it could damage the ice shelf.

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