n iceberg expected to be one of the 10 largest ever recorded is ready to break away from Antarctica, scientists say.

A long-running rift in the Larsen C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5,000 sq km piece from floating away.

Larsen C is the most northern major ice shelf in Antarctica.

Researchers based in Swansea say the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up.

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.

"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.

German Research Vessel Polarstern has found a location to begin its year-long drift in Arctic sea-ice.

The ship, which will head the North Pole's biggest scientific expedition, will settle next to a thick ice floe on the Siberian side of the ocean basin.

The precise location is 85 degrees north and 137 degrees east.

Hundreds of investigators will use it as a base from which to probe the impacts of climate change at the top of the world.

"After a brief but intensive search, we've found our home for the months to come," said expedition leader Prof Markus Rex, from the Alfred Wegener Institute (AWI).

"Greenland is losing ice seven times faster than it was in the 1990s.

The assessment comes from an international team of polar scientists who've reviewed all the satellite observations over a 26-year period.

They say Greenland's contribution to sea-level rise is currently tracking what had been regarded as a pessimistic projection of the future."

An 'atmospheric river' drove warm, moist air down over Antarctica

It was warm enough to rain over parts of the Antarctic coast