Antarctic's melting glaciers could be about more than warmer temperatures

Extract from ABC News

7.30

By Mark Horstman

Updated about 11 hours ago

Photo: A blue water lake runs into a waterfall over an ice shelf on the Sorsdal Glacier. (Supplied: Dave Lomas)

Related Story: Antarctic scientists search for warm water melting glacier

Map: Antarctica

An Australian team of international scientists is hoping to discover whether there's something more than warmer temperatures could cause Antarctic's glaciers to melt faster than expected.

Key points:

• Scientists concerned that meltwater is hastening glacier disintegration in Antarctica
• Meltwater gets under the ice through cracks and crevasses, speeding up glacier flow
• Three quarters of all Earth's freshwater is stored in glaciers
• At the current melt rate, it's estimated sea levels could rise 50 cms by 2100 from ice sheets alone

Photo: Glaciologist Dr Sue Cook is studying the effect of meltwater on glaciers in the Antarctica. (Supplied: Mark Horstman)

"The future of the Antarctic ice sheet is really important for everybody at the moment," glaciologist Dr Sue Cook told 7.30.

"We don't know how much ice it's going to lose over the next decades, and it's going to contribute to sea-level rise."

Glaciers cover just a 10th of the Earth's land surface, but they store around three quarters of the planet's fresh water.
That means that they play a crucial effect on climate change.
"Being able to tell how much it's going to contribute to that is going to be really important for everybody," Dr Cook said.
If they continue to melt at their current rate, it's estimated that the ice sheets alone will add around 50 centimetres to sea level by the end of this century.
Why and how this is happening has serious implications for low-lying cities and island nations.

More to disintegrating glaciers than warmer temperatures

Photo: Aerial of the edge of the Sørsdal Glacier, eastern Antarctica, in February. (Supplied: Mark Horstman)

The fate of glaciers rests on a massive balancing act between snowfall and ice melt.
"The ice sheet is gaining mass every year as snow falls on to the upper layers, and as it moves downstream and encounters the ocean it'll start melting where it contacts water, and then lose icebergs as well." Dr Cook explained.
"So, they're the two ways it's losing ice."

"What we're interested in is the balance between those two processes — how much ice is it gaining as snow, versus how much it's losing."

But there's more to this than just warmer temperatures melting ice.
Research in Greenland has shown that most of the loss from its ice sheet comes from meltwater speeding up the flow of its glaciers.

Photo: Meltwater runs into a fissure on the Sorsdal Glacier. (ABC Catalyst: Kevin May)

Vivid blue meltwater from surface lakes on the glacier is disappearing down cracks and fissures and flowing under the ice.
"As the water goes down a crevasse, the pressure of the water can open it up," Dr Cook said.
"If you have a big enough volume of water, that crevasse can go all the way to the base and then the water is instantly injected into the base of the ice sheet. And that changes how fast it's flowing."
If water gets to the base, where ice grinds against bedrock, it can lubricate the glacier and make it flow faster, accelerating ice sheet loss.

First project of its type in Antarctic

Photo: Dr Christian Schoof's research team set up on the Sorsdal Glacier (Supplied: Christian Schoof)

After the discovery of the phenomenon in Greenland, there is now concern that the same thing is happening in the Antarctic.
Using a variety of instruments from thermometers to time-lapse cameras, the team is making a detailed survey of the Sorsdal Glacier in eastern Antarctica.
Associate Professor Christian Schoof, from the University of British Columbia, is the Antarctic project leader hoping to discover what is actually happening inside the glacier.
"The realisation that this can actually happen is about 14 years old, and that's really generated the interest that we've seen in Greenland," he told 7.30.

"The focus on Antarctica is very, very recent. We're one of the first projects on the ground trying to look at this."

In December, the science team witnessed an incredible waterfall plummeting off the edge of the ice shelf.
And they have found a lake that appears to have drained, but are yet to discover where the water went.
"It's so important for us to be out here monitoring what the ice sheet looks like at the moment, and then we can find out if its changing over the next few years," Dr Cook said.
This research season on the Sorsdal is the first of what the scientists hope will be many more, to build a better understanding of the forces that drive glaciers.