Satellite data shows that Antarctic sea-ice is well below any previously recorded winter level, alarming experts.
"It's so far outside anything we've seen, it's almost mind-blowing," Walter Meier, who monitors sea-ice with the National Snow and Ice Data Centre told the BBC.
Currently, the ice floating on the surface of the Antarctic Ocean measures less than 17 million sq kms — 1.5 million sq kilometres of sea-ice less than the September average.
The area of missing ice is about five and a half times the size of New Zealand.
Polar experts warn that an unstable Antarctica could have far-reaching consequences.
The white surface of Antarctica's massive ice plains reflect the Sun's energy back into the atmosphere, also cooling the water below and near it.
Dr Caroline Holmes at the British-Antarctic Survey said that the impacts could become more pronounced during summer months.
Melting sea-ice exposes dark areas of ocean, which absorb sunlight rather than reflecting it. This means that the water gets warmer, resulting in more ice melting. This creates a feedback loop of ice melting called the ice-albedo effect by scientists.
Since the 1990s, a 7.2mm increase in sea level can be attributed to melting Antarctic ice.
Even small increases to sea levels could result in storm surges that could inundate coastal communities. Millions of people would be impacted if significant amounts of land ice were to start melting.
The remoteness of the frozen continent and lack of historical information make it difficult for scientists to monitor changes.
They know the extent of the sea-ice, but not the thickness.
Dr Robbie Mallet and other scientists are still trying to determine the causes of the vanishing winter ice.
"There is a chance that it's a really freak expression of natural variability," he told the BBC, meaning that a number of natural factors could have built up and are simultaneously impacting the region.
Record ocean temperatures are likely a contributing factor as warm water will not freeze, scientists suggest.
Changes in ocean currents and the winds that drive temperatures in the Antarctic could also be having impacts.
The currently developing El Niño weather phenomenon could also be subtly contributing to shrinking sea-ice, although it is still weak.
Dr Mallet said there are "very, very good reasons to be worried."
"It's potentially a really alarming sign of Antarctic climate change that hasn't been there for the last 40 years. And it's only just emerging now."
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