Antarctica's sea ice drops to an 'alarming low' for the third year in a row, scientists warn

Antarctica's sea ice has dropped to an 'alarming' low during the southern hemisphere's summer, scientists have revealed.  

Ice surrounding Earth's southernmost continent now measures less than 772,200 square miles (2 million sq km), or about the size of Mexico. 

Worryingly, this is the third year in the row that this figure has fallen below this threshold, according to the US National Snow and Ice Data Center (NSIDC). 

Less sea ice can threaten habitats for penguins, seals and other Antarctic animal life, and also contributes to a rise in global sea levels. 

Unfortunately, it follows a record-breaking low for Antarctica's sea ice during the winter as well. 

Antarctica's 'sea ice extent' refers to the ice surrounding the coastline of Antarctica. Here, the average sea ice extent for 1981 to 2010 for this time of the year is marked in orange - but in much of this area the ice is now 'missing'  

Sea ice plays an important role maintaining the Earth's energy balance while helping keep polar regions cool due to its ability to reflect more sunlight back to space. Pictured, sea ice in the water off Cuverville Island in the Antarctic

Walt Meier, a senior research scientist at NSIDC, said experts 'don’t yet know the full reason' why sea ice is now at a record low, although 'global warming certainly could be a factor'. 

'It appears that warm ocean temperatures are important, but other factors may be in play, including wind patterns,' he told MailOnline. 

'We have only 45 years of high quality data, which still may not capture all of the variability in the Antarctic sea ice.

'However, since 2016, Antarctic sea ice has mostly been much lower than normal with record lows at times.' 

Professor Martin Siegert, a glaciologist at the University of Exeter, agreed that 'we don't know for sure' what the cause is. 

'It would be good to have a definitive answer, but it doesn't actually matter that much,' he told MailOnline. 

'We certainly can't afford to assign it to variability as some excuse for not stopping fossil fuel burning – that would be crazy.'

Antarctica's sea ice is vitally important because the ice reflects the sun's light, helping to keep polar regions cool. 

Without this ice cover, dark patches of ocean are exposed instead, which absorbs sunlight rather than reflecting it – in turn, heating up the region and accelerating ice loss further. 

Climate scientists are constantly tracking sea ice extent throughout the seasons and comparing its size with the same months from previous years, in order to see how it's changing. Data from National Snow and Ice Data Center has recently showed that sea ice extent is lower than the average since records began, regardless of time of year

READ MORE: Antarctica sea ice reaches historic winter low

Map shows area of sea ice on September 17, 2023, compared with the average for winter

According to NSIDC, the five-day average of sea ice cover fell to 768,343 sq miles (1.99 million sq km) on February 18. 

It then dropped further to 764,482 sq miles (1.98 million sq km) on February 21. 

This is still not as severe as the record-breaking minimum ice extent set in February 2023 of 683,400 (1.77 million sq km). 

However, looking at the wider picture, the three lowest years on record are the last three years, according to scientists.

Ice sheet surface melt on the Antarctic Peninsula abruptly dropped in mid-January and remained low through February 15 

Because it's summer in the southern hemisphere, most Antarctica ice currently there is estimated to be only about 3 feet to 6.5 feet (1-2 metres) thick. 

Dr Ariaan Purich, a climate scientist at Monash University in Australia, thinks the ice is thinner than usual since it reformed after the winter. 

'It seems plausible, and thinner sea ice could melt back more quickly,' Dr Purich told the Guardian. 

Antarctica's 'sea ice extent' refers to the ice surrounding the coastline of Antarctica, and does not include the ice covering the landmass itself. 

Due to more frigid temperatures, the sea ice reaches a maximum extent in the southern hemisphere's winter (July to September).

But temperatures gradually rise and it reaches a minimum extent during the southern hemisphere's summer (December to February). 

Just like in the Arctic, the surface of the ocean around Antarctica freezes over in the winter and melts back each summer. Antarctic sea ice (pictured) usually reaches its annual maximum extent in mid- to late September (winter), and reaches its annual minimum in late February or early March (summer)

Climate scientists are constantly tracking sea ice extent throughout the seasons and comparing its size with the same months from previous years, in order to see how it's changing 

So although there's great variability in the ice extent depending on time of year, it's lower than the average since records began, regardless of the season. 

Last year, during the southern winter, NSIDC reported that Antarctica's sea-ice levels are at a 'mind-blowing' historic low for the time of year of less than 6.5 million square miles (17 million sq km). 

This is 580,000 square miles (1.5 million sq km) less than the average for September – and equates to five times the size of the British Isles. 

Melting ice in parts of the Antarctica - including the Antarctic Peninsula - were also above average between mid January and mid February 

In a recent blog post, NSIDC also said weather conditions from January 15 to February 15 continued to be warm in central West Antarctica, where air temperatures were 4°F (2°C) above the 1991 to 2020 average.

Meanwhile, ice on the Antarctic Peninsula – the part of the continent that sticks out like a tail – abruptly dropped in mid-January and remained low through February 15.  

Rapid warming has already caused a significant southward shift and contraction in the distribution of Antarctic krill – a keystone species, campaigners said.

A recent Greenpeace expedition to the Antarctic also confirmed that Gentoo penguins are breeding further south as a consequence of the climate crisis.