Scientists solve the mystery of why global warming and melting has increased ice around Antarctica

 Climate change experts have been trying for years to explain why the sea ice in Antarctica is
expanding.

Now scientists claim to have found the answer – global warming.

They believe the paradoxical shift is caused by water melting from beneath the Antarctic ice shelves and re-freezing back on the surface.

 The frozen sea around the South Pole has been steadily growing, reaching a record extent in the winter of 2010, while the Arctic ice at the north of the planet shrank to a record low last year.

Now a team from the respected Royal Netherlands Meteorological Institute says that the fresh water melting from the Antarctic ice sheets has a relatively low density compared to the denser salty seawater, so it accumulates in the top layer of the ocean during the summer months.

The surface waters re-freeze during autumn and winter to spread across a greater area.

The Dutch study, published yesterday in the journal Nature Geoscience, says: ‘Sea ice around Antarctica is increasing despite the warming global climate. This is caused by melting of the ice sheets from below. This powerful negative feedback counteracts Southern Hemispheric atmospheric warming.’

The researchers predict the phenomenon will continue.

The Earth’s poles have very different geography. Surrounded by North America, Greenland and Eurasia, the Arctic ice cap floats on the ocean, not land. It has lost a large amount of its older, thicker sea ice over the last 30 years, making it more vulnerable to the warming trend.

The Antarctic, however, is a continent circled by open waters that lets sea ice expand during the winter but also offers less shelter during the melt season.

The Dutch report notes that despite the increase in surface ice expansion each winter, the total mass of ice around Antarctica is continuing to shrink because of the underwater ice melt. The study is not the first to put forward a reason for the Antarctica effect. However, there is some scepticism about the findings.
Paul Holland of the British Antarctic Survey stuck to his findings in a report last year that a shift in winds linked to climate change was blowing a layer of meltwater further out to sea and adding to winter ice.

‘The possibility remains that the real increase is the sum of wind-driven and meltwater-driven effects, of course. That would be my best guess, with the meltwater effect being the smaller of the two,’ he said.

The Dutch report also speculated that a cold layer of water created offshore may be responsible for lower than average snowfall in Antarctica, as it cools the air above it. Cold air can hold less moisture than warm.

‘Cool sea surface temperatures around Antarctica could offset projected snowfall increases in Antarctica, with implications for estimates of future sea-level rise,’ said the study.

At a winter maximum in September, ice on the sea around Antarctica covers about 7.3million square miles, bigger than Antarctica’s land area.

The scientists say the Antarctic sea ice has shown a small but significant growth of 1.9 per cent per decade since 1985.