Colin O'Brady, 33, finished the 1,482 kilometer (921 mile) north-to-south trek across the frozen continent in 54 days.

O'Brady and British Army Captain Louis Rudd, 49, departed separately on November 3 from Union Glacier on a race across Antarctica alone and unassisted. Rudd is still one or two days behind.

Read more: Rate of Antarctic ice melt triples since 2012, study finds

The two set off on cross-country skis dragging 180 kilogram (400 pound) sleds across the unforgiving landscape, which in 2016 claimed the life of Englishman Lieutenant Colonel Henry Worsley as he attempted a similar unassisted solo crossing of Antarctica.

O'Brady had to carry all of the supplies he would need on the journey. "The reason it’s been said that this crossing is impossible is that in order to have enough food to make the crossing you have to start with a very heavy sled," he wrote on day four of the trek.

In 1997, Norwegian polar explorer Borge Ousland completed the first solo crossing of Antarctica but he was aided by kites.

O'Brady made a decision over breakfast on Christmas to make a final 125 kilometer push to arrive on Wednesday at a marker on the Ross Ice Shelf, where Antarctica's land mass ends and sea ice over the Pacific Ocean begins. It took him 32 hours without sleep.

O'Brady faced blasting wind, snow drift, sub-freezing temperatures

"While the last 32 hours were some of the most challenging hours of my life, they have quite honestly been some of the best moments I have ever experienced. I was locked in a deep flow state the entire time, equally focused on the end goal, while allowing my mind to recount the profound lessons of this journey," he wrote on Instagram, where he kept daily records of the adventure.

"It always seems impossible until it's done," he wrote, quoting former South African President and anti-apartheid hero Nelson Mandela.

O'Brady making a phone call from the end of the continent, marked by a pole before the beginning of the Ross Ice Shelf

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