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hubie [soylentnews.org] writes:

The ship wasn't designed to withstand the powerful ice compression forces—and Shackleton knew it [arstechnica.com]:

In 1915, intrepid British explorer Sir Ernest Shackleton [wikipedia.org] and his crew were stranded for months in the Antarctic after their ship, Endurance [wikipedia.org], was trapped by pack ice, eventually sinking into the freezing depths of the Weddell Sea. Miraculously, the entire crew survived. The prevailing popular narrative surrounding the famous voyage features two key assumptions: that Endurance was the strongest polar ship of its time, and that the ship ultimately sank after ice tore away the rudder.

However, a fresh analysis reveals that Endurance would have sunk even with an intact rudder; it was crushed by the cumulative compressive forces of the Arctic ice with no single cause for the sinking. Furthermore, the ship wasn't designed to withstand those forces and Shackleton was likely well aware of that fact, according to a new paper published in the journal Polar Record. Yet he chose to embark on the risky voyage anyway.

Author Jukka Tuhkuri of Aalto University is a polar explorer and one of the leading researchers on ice worldwide. He was among the scientists on the Endurance22 mission that discovered the Endurance shipwreck in 2022, documented in a 2024 National Geographic documentary [arstechnica.com]. The ship was in pristine condition partly because of the lack of wood-eating microbes in those waters. In fact, the Endurance22 expedition's exploration director, Mensun Bound, told The New York Times at the time that the shipwreck was the finest example he's ever seen; Endurance was "in a brilliant state of preservation."

[...] Once the wreck had been found, the team recorded as much as they could with high-resolution cameras and other instruments. Vasarhelyi, particularly, noted the technical challenge of deploying a remote digital 4K camera with lighting at 9,800 feet underwater, and the first deployment at that depth of photogrammetric and laser technology. This resulted in a millimeter-scale digital reconstruction of the entire shipwreck to enable close study of the finer details.

It was shortly after the Endurance22 mission found the shipwreck that Tuhkuri realized that there had never been a thorough structural analysis conducted of the vessel to confirm the popular narrative. Was Endurance truly the strongest polar ship of that time, and was a broken rudder the actual cause of the sinking? He set about conducting his own investigation to find out, analyzing Shackleton's diaries and personal correspondence, as well as the diaries and correspondence of several Endurance crew members.

[...] Endurance was originally named Polaris; Shackleton renamed it when he purchased the ship in 1914 for his doomed expedition. Per Tuhkuri, the ship had a lower (tween) deck, a main deck, and a short bridge deck above them which stopped at the machine room in order to make space for the steam engine and boiler. There were no beams in the machine room area, nor any reinforcing diagonal beams, which weakened this significant part of the ship's hull.

[...] Based on his analysis, Tuhkuri concluded that the rudder wasn't the sole or primary reason for the ship's sinking. "Endurance would have sunk even if it did not have a rudder at all," Tuhkuri wrote; it was crushed by the ice, with no single reason for its eventual sinking. Shackleton himself described the process as ice floes "simply annihilating the ship."

Perhaps the most surprising finding is that Shackleton knew of Endurance's structural shortcomings even before undertaking the voyage. Per Tuhkuri, the devastating effects of compressive ice on ships were known to shipbuilders in the early 1900s. An early Swedish expedition were forced to abandon their ship Antarctic in February 1903 when it became trapped in the ice. Things progressed much like Endurance: the ice lifted Antarctic up so that the ship heeled over, with ice-crushed sides, buckling beams, broken planking, and a damaged rudder and stern post. The final sinking occurred when an advancing ice floe ripped off the keel.

Shackleton knew of Antarctic's fate and had even been involved in the rescue operation. He also helped Wilhelm Filchner [wikipedia.org] make final preparations for Filchner's 1911-1913 polar expedition [wikipedia.org] with a ship named Deutschland [wikipedia.org]; he even advised his colleague to strengthen the ship's hull by adding diagonal beams, the better to withstand the Weddell Sea ice. Filchner did so and as a result, Deutschland survived eight months of being trapped in compressive ice, until the ship was finally able to break free and sail home. (It took a torpedo attack in 1917 to sink the good ship Deutschland.)

The same shipyard that modified Deutschland had also just signed a contract to build Endurance (then called Polaris). So both Shackleton and the ship builders knew how destructive compressive ice could be and how to bolster a ship against it. Yet Endurance was not outfitted with diagonal beams to strengthen its hull. And knowing this, Shackleton bought Endurance anyway for his 1914-1915 voyage. In a 1914 letter to his wife, he even compared the strength of its construction unfavorably with that of the Nimrod, the ship he used for his 1907-1909 expedition. So Shackleton had to know he was taking a big risk.

"Even simple structural analysis shows that the ship was not designed for the compressive pack ice conditions that eventually sank it," said Tuhkuri [eurekalert.org]. "The danger of moving ice and compressive loads—and how to design a ship for such conditions—was well understood before the ship sailed south. So we really have to wonder why Shackleton chose a vessel that was not strengthened for compressive ice. We can speculate about financial pressures or time constraints but the truth is we may never know. At least we now have more concrete findings to flesh out the stories."

Both TFA and the open-access journal reference are very interesting reads.

Journal Reference: Polar Record, 2025. 10.1017/S0032247425100090 [doi.org]

Original Submission