Researchers have studied the records of pioneering explorers, including Captain Robert Scott and Sir Ernest Shackleton.
The study suggests that Antarctic sea-ice is much less sensitive to climate change than the Arctic, which has declined dramatically.
The research has been published in The Cryosphere journal.
A century ago Captain Scott and Sir Ernest Shackleton were among those who ventured into completely uncharted territory.
They were the bravest explorers of their age. At the time, their voyages brought a totally new understanding of the Antarctic landscape.  And now their records are giving scientists new data on the impacts of climate change.
Some data collected by whaling vessels suggests the extent of Antarctic summer (December, January, February, March) sea-ice was significantly higher during the 1950s, before a steep decline returned it to around six million square kilometres (average across the four months) in recent decades.
But the log books of the "heroic explorers" show that over the long term, the amount of ice has changed very little. It has merely ebbed and flowed.
Dr Jonathan Day of the University of Reading who led the study says his analysis indicates that the extent of Antarctic summer sea-ice is at most 14% smaller now than during the early 1900s.
"The Antarctic sea-ice a hundred years ago was fairly similar to what it is today. That is not much if you contrast this with the Arctic which has lost 26% of its extent," he told BBC News.
Dr Day says his results suggest the climate of Antarctica may have fluctuated significantly throughout the 20th Century, swinging between decades of high ice cover and decades of low cover, rather than a steady downward trend.
"We know that sea-ice in the Antarctic has increased slightly over the past 30 years, since satellite observations began. Scientists have been grappling to understand this trend in the context of global warming, but these new findings suggest it may not be anything new.
"If ice levels were as low a century ago as estimated in this research, then a similar increase may have occurred between then and the middle of the century, when previous studies suggest ice levels were far higher."
Captain Scott died along with his team in 1912 after missing out on being the first to reach the South Pole by a matter of weeks. Shackleton's ship sank after becoming trapped in ice in 1915 as he and his crew attempted the first ever cross-Antarctic trek.
Scott and Shackleton went to the Antarctic in search of glory - but a century on - their ultimate  legacy will be to have helped scientists learn more about climate change.
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Sum: Log books from the early Antarctic expeditions indicate that the area of summer sea-ice around the continent has barely changed in size in a century.
Q: Publishers Herald Newspapers Plc said the Ceredigion Herald will be published mainly in English but with "more Welsh content" than other weeklies.
It joins stablemates the Pembrokeshire Herald, the Carmarthenshire Herald and the Llanelli Herald.
It will have an initial print run of 10,000 and will cover from Aberystwyth to Cardigan in Ceredigion.
Managing editor Thomas Sinclair said: "I very much hope that the new paper will be as well received as the other three titles."
Publishers said the Ceredigion Herald will have three or four pages of Welsh every week and will also allow readers' letters, contributors' columns and obituaries in Welsh.

A: A new weekly newspaper, featuring both English and Welsh language content, will be launched on Friday.
Text: Emergency crews were called to the Mereside Industrial Park at Fenns Bank, on the Wrexham-Shropshire border at 12:10 BST.
Shropshire Fire and Rescue Service from Whitchurch attended, however the man in his 30s was released before they arrived and died at the scene.
Investigations into the incident are continuing.
summary: A man has died after becoming trapped in heavy machinery at a Wrexham industrial estate.
Article: Jayangani scored 178 not out to lead Sri Lanka to 257-9 at Bristol.
But Australia captain Meg Lanning, who is the top-ranked ODI batswoman, hit an unbeaten 152 as her side (262-2) chased down Sri Lanka's total inside 44 overs.
At Taunton, Smriti Mandhana made 106 not out as India beat West Indies by seven wickets.
Jayangani's knock included six sixes and 22 fours and gave her the highest proportion of runs (69.2%) scored by an individual in a women's ODI innings.
But she was one of only three Sri Lankan players to reach double figures as Australia pulled off a tournament-record chase
"This is the best performance in my life," Jayangani, 27, told BBC Sport.
"I played my normal game," she added. "The first 30 overs I tried to go for singles and not boundaries, then I tried to hit the ball after the power play, for sixes and fours over the rope."
Lanning, who hit her 11th international century, paid tribute to her opponent.
"The way she was hitting the ball was incredible and very hard as well," said the 25-year-old. "She was just swinging hard and connecting and it certainly was a very special innings."
Mandhana followed her 90 in the shock win against England in the tournament opener by steadying the ship after India lost two early wickets, hitting 13 fours and two sixes.
She added 108 runs for the third wicket with captain Mithali Raj (46) as India chased a modest 184.
Mandhana told BBC Sport she is confident her team can win the competition.
"We are looking good, the batsmen are doing their job, the bowlers are doing their jobs and we are feeling well also," she said. "Hopefully we will continue the same form throughout the World Cup and on 23 July I will lift the World Cup."
Sri Lanka face England next at Taunton on Sunday, a day when all eight teams are in action.
Australia take on New Zealand at Bristol, India face Pakistan in Derby and South Africa play West Indies at Leicester.
++++++++++
Summarize:
Chamari Athapaththu Jayangani hit the third highest women's one-day score but Sri Lanka still lost to Australia by eight wickets at the World Cup.