East Antarctic ice sheet melt faster than expected

Updated November 24, 2009 10:02:08

A new study shows that the world's largest ice shelf has lost almost 60 billion tonnes of ice per year for the past three years - long thought to be largely unaffected by climate change.

The new study by scientists at the University of Texas uses measurements from NASA satellites. The scientists say that if this ice sheet continues to melt it may cause sea levels to rise sooner than expected.

Presenter: Jennifer Macey
Speaker: Dr Roland Warner, glaciologist with Australian Antarctic Division; Professor Nathan Bindoff from the Antarctic Cooperative Research Centre in Hobart

WILLIAMS: It's a bit hard to say whether this is a response to climate change because the icebergs that we're seeing in New Zealand are probably from the same big event, the same big iceberg carving off Antarctica as the ones we saw in 2006. Just these icebergs have been grounded for a bit longer along the way.

COUTTS: Ok and where are they, and can you just give us an idea of their dimensions?

WILLIAMS: So the largest one is probably about 250 metres long probably by about 100 metres wide with as much as 50 metres showing above the water line, which of course means that about another 300 metres under the water. And they're roughly sort of due south of the southeast corner of New Zealand's South Island.

COUTTS: You're expecting them to get how close to New Zealand?

WILLIAMS: I'm sitting on the fence a little bit on this one because what happened, the icebergs are following the similar track for last time, 2006, so that sort of gives us some confidence that they'll come close to New Zealand. But what we also saw in 2006 was when they got very close a lot of them got blown away out to the east and sort of away from helicopter range and away from the shore. So they were there but people couldn't see them.

COUTTS: How many of them altogether?

WILLIAMS: Well the largest estimate is that there's around, probably realistically there's around four to five that are coming towards New Zealand, but satellite studies by colleagues at the Australian Antarctic Division have shown that there's as many as 100 in the southern ocean due south of New Zealand. So we may get more if those are pushed north.

COUTTS: Well it's a largest body of solid water, solid mass, four to five of them in the dimensions you've described. If they do get closer to New Zealand and they melt, continue to melt I should say, what kind of impact are you expecting it may have?

WILLIAMS: The sort of temperature impact on the water isn't very much. I mean these large icebergs, despite their size, it's a bit like throwing four or five ice cubes in a bath. It's not really going to change the temperature a lot. But what they can do is there's a lot of glacial debris from when they were gouging out of the Antarctic ice sheet inside the ice, and this is a sort of a fine powder. When that gets released into the water that can provide extra nutrients and we can have little blooms in phytoplankton, so the very bottom of the food chain and that can be important depending on exactly where it happens.

COUTTS: So is this to your organisation like the Haley Comet of the region? Are you out there in your dinghies now trying to study these huge masses of water that are floating towards New Zealand?

WILLIAMS: For us they're more an item of public interest rather than scientific interest because if we really want to understand the sort of changes around Antarctica then we really need to be looking at the icebergs carving in Antarctica rather than when they're arriving in New Zealand.

COUTTS: Well that's a contentious issue isn't it, the changes in Antarctica?

WILLIAMS: Absolutely and large icebergs only carve every 30 to 50 years, so trying to detect the change in how often large icebergs carve is incredibly difficult.

COUTTS: Well this time, if it's 2006 the last time to now, it's only three years.

WILLIAMS: Yeah but what we think is these are the same. We think these all came from, there were six large icebergs that carved off the Ross Ice Shelf, so that's sort of due south of the Pacific, and so those icebergs carved between 2000 and 2002, and we think it's the remains of one of those. We haven't been able to pinpoint exactly which one because during the polar night it's a bit difficult to keep track of them in the Southern Ocean when we can't see them. But we're fairly sure it's likely to be one of those ones, and that's where the 2006 ones came from. So we think these ones just got stuck, which icebergs do all the time round Antarctica, they run aground and they just sit there. Some of them have sat there for the best part of a decade.