Sinking of the "Endurance": Was Ernest Shackleton to blame?

The spectacular images went around the world: more than 100 years after it sank, the famous research vessel "Endurance" was found at the bottom of the Weddell Sea at a depth of 3008 metres in 2022. The images show a remarkably well-preserved ship with the name "Endurance" still visible on the stern. They barely give an idea of the massive forces with which icebergs and pack ice beset her for months and how Shackleton and his crew fought to save her. The fight was in vain. Eleven months after the pack ice had taken the almost 44-metre-long schooner barque in its grip, it sank on 21 November 1915.

Shackleton and his crew, who had set out to be the first people to cross Antarctica, had to make their way north on foot with the dinghies in tow. The adventure of their successful rescue gave polar explorer Ernest Shackleton hero status.

But now a new study has shed a different light on the history of the failed Antarctic expedition from 1914 to 1916. Engineer Jukka Tuhkuri from Finland's Aalto University has for the first time analysed the history of the expedition. Structural analysis of the "Endurance" undertaken. He comes to the conclusion that Shackleton deliberately chose an unsuitable ship for the dangerous journey and accepted the risks for his crew.

Unsuitable ship despite better alternatives

When the "Endurance" - then still known as the "Polaris" - was launched on 17 December 1912 in Sandefjord, Norway, its purpose was clear: to take tourists to the edge of the Arctic in the Arctic summer, to the Greenland Sea and to Spitsbergen. With extra-thick planking and equally thick frames, she is ideally equipped for the conditions at the edge of the pack ice. Her comparatively straight hull shape gives her quite good sailing characteristics and should allow her to glide well through the ice floes. "But the conditions at the edge of the pack ice in the Arctic are very different from those deep inside the pack ice in the Antarctic," writes Tuhkuri. "At the ice edge, the ships usually have to contend with collisions with ice floes. The Endurance was designed for these kinds of ice conditions, and her planking and frames were thick and strong enough for the task."

However, the schooner barque was never to fulfil this task. Her owner was struggling with financial difficulties and sold her to the adventurer Shackleton for his Antarctic expedition into the pack ice. The thickness of the planking and the frames is one thing, the Finnish engineer realises, but: "In pack ice conditions, where the pressure of the ice has to be taken into account, the deck beams are of crucial importance. They are what keep the two sides of the ship apart and maintain the shape of the ship. If the deck beams are not strong enough, a ship will be crushed by the pressurised ice." In this area in particular, but also in other design details, the "Endurance" differed from other expedition ships of its time.

What sets the "Endurance" apart from other expedition ships

Tuhkuri divides the polar ships of the late 19th and early 20th centuries into three structural categories: Wooden ships following the tradition of whalers, wooden expedition ships built for pack ice conditions, and steel icebreakers and other icebreaking vessels. The "Endurance" is an example of the first type. It is one of the last polar ships - if not the last - to be built in the tradition of wooden whalers and seal hunters, designed to operate at the ice edge because whales and seals can be found there, but not for the permanent pressure of being trapped in pack ice.

At the time the schooner barque was launched, there were already proven models for truly stable, wooden expedition ships. The most famous of these is probably the "Fram", developed by Fridtjof Nansen and Colin Archer especially for the pack ice. It was launched in 1893 and was first used by Nansen in his attempt to reach the North Pole by drifting with the ice in 1893-1896 and then by Roald Amundsen on his Antarctic expedition from 1910 to 1912.

The shape and size of the "Fram" is such that it is lifted by the ice that presses against its sides. This is ensured by an optimised, more oval hull shape and a short waterline length. Poor sailing characteristics, but excellent ice-capability. Retractable rudders and propellers also contribute to their safety in ice, but above all diagonal supports to reinforce the hulls. The latter in particular are retrofitted on many ships for polar voyages.

The "Endurance", on the other hand, sails into the pack ice without this additional reinforcement. Its large, open engine room also makes it particularly vulnerable. The 350 hp engine and steam boiler take up so much space that there is hardly any room for a stabilising tween deck. Longitudinally, there is a bulkhead in front of the engine room and another behind it, but vertically, the open space is only defined by the main deck and the keel. This means that the entire pressure load is borne by the main deck, while the stabilising deck beams lose strength due to their span. And the diagonal supports, which are particularly important, are unthinkable at this point without complex conversions.

What Shackleton knows about the stability of the "Endurance"...

In 1905, a ship initially named "Bjørn" was built at the Framnæs shipyard in Sandefjord for whaling and sealing in the Arctic, which was taken over by the German Wilhelm Filchner in 1910 and christened "Deutschland". Filchner plans the second German South Pole expedition and has modifications made to the ship at the Norwegian shipyard for this purpose.

He was advised by Ernest Shackleton, of all people, who visited the shipyard in early 1911. A few years earlier, Shackleton himself had already toyed with the idea of buying the "Bjørn" for his first Antarctic expedition from 1907 to 1909, but a chronic lack of sufficient cash for his endeavours was a recurring theme in the adventurer's life, so he undertook the journey on the less expensive "Nimrod".

Based on his experience, he now advises Filchner to reinforce the hull of the "Deutschland". Diagonal support beams were used and the deck beam span reduced, making the structure significantly more robust against compressive ice loads; according to Tuhkuri's calculations, the "Deutschland" could withstand one and a half times more ice pressure than the "Endurance", which was being built in the same shipyard at the same time as the "Deutschland" was being modified. The measure proved successful. Just one year later, Filsner reached the Weddell Sea and was trapped by pack ice. For eight months, his ship drifts with the ice in slow motion, but is eventually freed unharmed - two years before Shackleton is due to set off with the "Endurance".

The successes of the "Fram", the "Deutschland" and other ships have shown how a ship must be designed to withstand the enormous demands of the Antarctic, and Shackleton is aware of this. As well as the fact that with the "Endurance" he may have a ship with an excellent reputation, but certainly not the one with the best suitability. So he writes to his wife Emily from the road: "This ship is not as strong as the "Nimrod" in terms of construction, I saw that from her behaviour when she pressed against the dock wall here in a storm, but there is nothing to be afraid of, because I think she will get through the ice just fine. But I'd swap her for the old Nimrod any day, except for convenience." Nevertheless, he sails with her towards the South Pole. He will have had his reasons for doing so.

... and why he nevertheless embarks on this risky adventure

For a long time, Shackleton has been something of a dowdy child among respected polar explorers. The man of Irish origin was not a member of the honourable Royal Navy; he had only spent a few years in the merchant navy. Nevertheless, the highly respected Sir Robert Scott took him on board the "Discovery" in 1902 for a South Pole expedition. The Golden Age of Antarctic exploration had begun; the race to be the first to reach the Pole became known as the "heroic age".

Scott, the explorer and doctor Edward Wilson and Shackleton set off on foot from the frozen "Discovery" towards the Pole in dog sledges. But Shackleton falls ill with scurvy and has to travel temporarily on a dog sled. Scott later sends him home - Shackleton feels much better after eating plenty of fresh seal meat - as unfit for service. Shackleton, in his late 20s, penniless and poor in fame, denies his unfitness for service, but he has to comply. During this time, he may have developed a certain ambition to equal or even surpass Scott in the race to the Pole. At least that is what the British scientist Christopher Ralling surmises in the introduction to a book of Shackleton's letters and writings.

In order to achieve this, he had to lead his own expedition. In 1907-1909, during his second and first expedition, he travelled closer to the South Pole in the "Nimrod" than anyone before him. This brought him a certain degree of fame, but also doubts.

For a long time, he was busy paying off the mountain of debts with lectures and publications that his expedition had brought him. At the same time, a debate against his credibility was unleashed by the Royal Geographic Society, in particular by its distinguished member Sir Clements Markham. In September 1909, he wrote to the current president, Major Leonard Darwin: "As I am responsible for getting all this Antarctic business rolling, I think it right to let you know how I view recent developments. Shackleton's failure to reach the South Pole, when it could have been done by someone else, is really a matter of calculation and annoys me. (...) I can't accept the latitudes." Markham doubts that Shackleton and his men could have walked "pulling the sledge and half-fed, in a straight line fourteen miles a day, up a steep slope 9,000 feet above the sea, for twenty days".

The "other", the only person he believes can win the race to the Pole, is his protégé, Sir Robert Scott. The seeds of doubt about Shackleton's achievement have been sown and can no longer be eradicated. Scott hurriedly set about claiming the rights to the next expedition for himself. The idea that the two best expedition leaders in Great Britain would be most likely to succeed if they tackled the task together no longer occurred to anyone at this point. The rivalry was too great and only ended in 1913 with the news of the death of Scott and his companions, almost a year after they had died in an accident in the Eternal Ice while attempting to reach the South Pole - and also a year after Roald Amundsen had been the first to reach the Pole from his "Fram" and outdistanced his comrades-in-arms.

Shackleton does not let this get him down and develops his next major project: the crossing of the Antarctic continent. In a letter in The Times in December 1913, he announced an expedition for the following year in which he intended to cross the continent from sea to sea. He calls it the "Imperial Trans-Antarctic Expedition" - a British mission that is intended to generate patriotic feeling among the masses, not in scientific circles, and thus probably also raise money for his endeavour.

Generous support from the Royal Geographic Society is not to be expected; old doubts speak against this, as does Shackleton's refusal to subordinate the expedition solely to scientific benefit. He relied on public fundraising - with moderate success, which was just enough to purchase the "Endurance" and the necessary equipment. A costly modification was out of the question, neither financially nor for reasons of time. It is 1914, England is mobilising. The "Endurance" casts off, heading south. Shackleton writes to his wife after his departure: "I am only as good as an explorer and nothing more; I am hard and damned stubborn when I want something: altogether a generally unpleasant character. I love the struggle, and when things are easy, I hate it." At that moment, he probably doesn't realise just how simple things are about to become. He concludes: "Now that I'm working on my own work, I'll be better and more peaceful, and I don't think I'll ever go on another long expedition; I'll be too old." In fact, the challenging expedition that awaits him is to be his last.

The chronicle of the Endurance expedition

Despite the decision regarding the choice of boat, which is questionable from today's perspective, the story of the "Endurance" expedition remains an extraordinary chapter in polar research.

Read the hair-raising story of the Endurance expedition here

On 8 August 1914, the "Endurance" cast off from Plymouth and travelled to Antarctica via Argentina and South Georgia. The explorer ignores the warnings of whalers in South Georgia against travelling on. He travelled on. On 18 January 1915, however, the ship is stuck in the ice in the Weddell Sea. In ten months, it drifts 570 miles to the north-west in slow motion. The crew tried again and again to break up the ice around the ship, to steer it, to save her. "The behaviour of our ship in the ice," writes navigator Frank Worsley in his diary, full of confidence in the "Endurance", "has been excellent. Since we have been locked in, its steadfastness and endurance have always seemed beyond imagination. It would be sad if such a brave little ship were ultimately crushed by the merciless, slowly suffocating grip of the Weddell Pack, after ten months of the boldest and bravest fight any ship has ever put up." In October, however, the melting ice in all its mighty forms - ice floes here, an iceberg there - turns its grip into one of destruction.

In his book "South", Shackleton describes the condition as "strong pressure with twisting tensions that tore the ship from fore to aft": "The central part of the ship was pressed downwards, the ship leaned more and more to port and starboard until the Endurance settled on the ice floe and remained there, squeezed between ice floes and icebergs. The joints of the planks opened up by four to five inches on the starboard side, and at the same time we could see the ship bending like a bow under titanic pressure. Almost like a living being, it resisted the forces." The crew had to disembark and watch from their camp on an ice floe as their ship, possibly their only way home, slowly fell victim to the merciless ice. On 21 November, the "Endurance" finally sinks into the ice.

What follows is one of the most astonishing rescue operations in history. The 28 men fight their way to the uninhabited Elephant Island, first on foot and later with dinghies. From there, Shackleton and five of his men undertook a perilous 800-mile journey in an open boat to South Georgia, crossed the mountainous island on foot and reached a whaling station. After several failed attempts, he finally succeeded in rescuing the men left behind on Elephant Island on 30 August 1916. Despite all adversity, all 28 crew members survive - it is not his discoveries, it is this almost superhuman feat that makes Shackleton a British national hero.

Wreck found after more than a century

More than 100 years after its sinking, the wreck of the "Endurance" is discovered in March 2022 by an international team of researchers as part of the "Endurance22" expedition. The search is based on the detailed diary entries of Captain Frank Worsley. Hybrid autonomous underwater vehicles are used to search the seabed in a grid pattern until the wreck is found about four miles south of the position noted by Worsley. The images show a remarkably well-preserved ship, with the name "Endurance" still visible on the stern. The extensive damage, particularly to the rudder, keel and side planks, that caused her sinking is barely visible in this position. And they will always remain hidden, because according to the Antarctic Treaty, the wreck is considered a "cultural property of mankind" and may not be salvaged.