The under-side of one of the largest floating ice shelves in the southern oceans is not melting as expected, according to experts.

Scientists drilling along the western coast of Antarctica found that the Ross Ice Shelf is actually freezing - but they have no idea why.

The finding might explain why the ice shelf is considered more stable than many of the region's other floating shelves.

If sea water freezes to the bottom of the ice periodically, this would help shore up the shelf and protect it from thinning.

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The under-side of one of the largest floating ice shelves in the southern oceans is not melting as expected, according to experts. Scientists drilling along the western coast of Antarctica found that the Ross Ice Shelf is actually freezing - but they have no idea why

Researchers from New Zealand used a hot water drill to dig deep into the floating ice shelf, roughly the size of Spain and around half a mile thick (1km).

Experts then lowered a camera into the hole they had melted, using a thermometer and other instruments to study the ice shelf's history.

Rather than finding the evidence they expected to confirm the recent melting, they came across jagged icy crystals.

If the shelf was melting, the sides of the borehole would have instead been smooth.

'It blew our minds,' said Christina Hulbe, a glaciologist from the University of Otago in Dunedin, New Zealand, who co-led the expedition, speaking to New Scientist.

The team, which included hot water drillers, glaciologists, biologists, seismologists and oceanographers, set up camp around 200 miles (350 km) from the ice shelf's front.

They worked from November 2017 through to January, supported by tracked vehicles and, when the notorious local weather permitted, Twin Otter aircraft.

As with all polar oceanography, getting to the ocean was often the most difficult part.

In this case, the team faced the complex task of melting a bore hole, only 25 centimetres (ten inches) in diameter, through hundreds of metres of ice.

Writing in The Conversation, Dr Hulbe added: 'Once the instruments were lowered more than 300m (980 ft) down the bore hole it becomes the easiest oceanography in the world.

'You don’t get seasick and there is little bio-fouling to corrupt measurements.

The finding might explain why the ice shelf is considered more stable than many of the region's other floating shelves at present. The team worked from November through to January, supported by tracked vehicles

If sea water freezes to the bottom of the ice periodically, this would help shore up the shelf and protect it from thinning. This image show the team at work, preparing a mooring

'There is, however, plenty of ice that can freeze up your instruments or freeze the hole shut.'

It's not exactly clear why the Ross Ice Shelf is freezing, when others in the region are thawing and even sheering.

The team has left behind a number of instruments down the hole to continue to monitor the health of the ice shelf.

They are now looking for signs within the shelf to see if it has had past melting episodes.

If Ross and four other ice shelves in the south are unable to hold back the ice from melting, it is estimated global sea levels could rise by up to ten feet (three metres).

The team, which included hot water drillers, glaciologists, biologists, seismologists and oceanographers, set up camp around 200 miles (350 km) from the ice shelf's front. This satellite map shows the camp site on the Ross Ice Shelf

As with all polar oceanography, getting to the ocean was often the most difficult part. This image shows the continent of Antartica, with the Ross Ice shelf in the bottom left