A century after the Endurance sank under the Antarctic ice, new research has revealed that the ship was never as strong as legend suggested — and that Sir Ernest Shackleton knew it. Praised for decades as the pinnacle of polar engineering, Endurance was structurally flawed at the time of its construction, and its weaknesses left it catastrophically vulnerable to the pack-ice-crushing forces of the Weddell Sea.

Stern of Endurance as uncovered on March 7, 2022. Credit: Endurance22 / CC BY-SA 4.0

The new research, published in Polar Record on October 6, combines engineering analysis with archival information, including diaries, crew journals, and Shackleton’s own correspondence. Directed by Jukka Tuhkuri, an Aalto University professor of solid mechanics and an ice mechanics specialist, the study dispels one of the most enduring myths of the Heroic Age of Antarctic Exploration — that Endurance was the strongest wooden ship ever built and was lost solely because its rudder was torn off.

In fact, the ship’s sinking was more complex — and more preventable. According to the study, Endurance was never designed to withstand compressive ice conditions. It had a large, extensive engine room, which weakened the central hull and lacked diagonal beams that would have made its structure stiff against shifting ice. Its deck beams and frames were also thinner than those of other polar ships built around that time. Compared to ships designed for heavy compression, Endurance performed poorly in every way it was ᴀssessed.

Historical accounts show that Shackleton was aware of these weaknesses prior to the 1914 expedition. In letters to his wife, he admitted that Endurance was weaker than his previous ship, and he even suggested improvements — including diagonal supports — for polar vessels years earlier. Ironically, one of those ships, the Deutschland, took his advice and survived months trapped in similar Antarctic ice conditions.

Idealised cross-sections of early Antarctic ships. Thick arrows represent compressive ice load. Endurance, Discovery, Belgica, Scotia, and presumably Aurora, were of the type (a); Fram, Gauss and Deutschland were of the type (b). Credit: J. Tuhkuri, The Polar Record (2025)

The study also disputes the long-standing claim that the destruction of the rudder alone had doomed the ship. While it was true that the rudder had been destroyed, the true cause of the sinking was that the keel and the hull collapsed under extreme pressure. The ice did not just damage Endurance — it crushed it completely.

The conclusions were reached after Tuhkuri joined the 2022 Endurance22 expedition, which successfully rediscovered the wreck of Endurance almost 3,000 meters below the Weddell Sea. The discovery motivated Tuhkuri to conduct a detailed structural analysis, concluding that the ship’s mythical image had overshadowed its engineering deficiencies.

Endurance’s final sinking in Antarctica. Public Domain

Even though the study raises difficult questions regarding Shackleton’s choices, it does not blame him outright. Time limitations, financial considerations, or misplaced optimism may have been factors, but the precise reasons remain uncertain. As Tuhkuri indicates, it is clear that Shackleton knowingly took a vessel unfit for the brutal Antarctic environment — a decision that sealed the fate of one of the most iconic exploration vessels in history.

More than a century later, the Endurance legend still represents human courage and resilience in the face of the fury of nature. But, as this new research reveals, even heroes are not immune to the consequences of faulty design and decisions made under pressure.

More information: Tuhkuri, J. (2025). Why did endurance sink? The Polar Record, 61(e23). doi:10.1017/s0032247425100090