Making subsea history by locating Endurance

In March 2022, almost precisely 100 years after the burial of famed British polar explorer Ernest Shackleton, his legendary ship Endurance was finally located at the bottom of the Weddell Sea in Antarctica. In this exclusive interview, Nico Vincent talks about the challenges involved in surveying at more than 3,000m depth, and provides insight into the state-of-the-art hydrographic technology used to overcome the unique sea ice conditions. 

What was your role in the 2022 search for Endurance?

When a previous mission to find Endurance had unfortunately been unsuccessful in 2019, the Falklands Maritime Heritage Trust (FMHT) decided to organize its own expedition to locate the wreck. In 2020, I was delighted to be appointed by the benefactor of the FMHT as subsea project manager of this expedition, called Endurance22. After accepting the role, I immediately asked for a detailed ‘lessons learned’ report explaining all of the issues encountered in 2019. In fact, that illustrates just one of the parallels between Shackleton’s story and our own – it’s essentially a story of failure, because without those earlier failures, we could never have achieved success this time around.

What were the key considerations when selecting the equipment for surveying at a depth of 3,000m in sea ice?

The 2019 expedition had used a Kongsberg HUGIN autonomous underwater vehicle (AUV), but it was lost and the mission had to be abandoned. I truly believe the HUGIN is the fastest and most efficient vehicle on the market. But it’s not a question of quality; it’s about picking the right vehicle for the right job. If you’re driving on the snow, you really need a four-wheel-drive vehicle, not a Formula 1 race car like the HUGIN. So the senior management at Ocean Infinity, the project’s subsea contractor, suggested the Saab Sabertooth: a rugged, robust and reliable hybrid AUV/ROV. In fact, we took two of them along with us – ‘Ellie’ and ‘Doris’ – but in the end only Ellie was used.

To avoid the Sabertooth becoming lost, as the HUGIN was, we decided to tether it to the vessel using a 3mm-diameter Kevlar-encased fibre-optic cable, and deploy it as a ‘wired AUV’. This would give us full manual control in case of emergency, and also ensured that the data would be transmitted to our on-board control room in real time. To protect the delicate tether from the ice and also help us monitor it, the engineering team designed a steel collar: a 9m length of pipe equipped with a circular yellow buoy on top, like a big fishing float.

I knew time would be our enemy on the expedition – and, in sea ice, everything takes four or five times longer – so I was always looking for ways to save time. For example, even though the maximum acoustic tracking slant range of our equipment was 12km, I had 25km of cable fitted to the winch so that we wouldn’t have to waste time respooling in the case of failure.

For surveying mode, the AUVs were equipped with sidescan sonar; we chose the EdgeTech 2205 for its long range and efficient coverage, with an R2Sonic 2024 multibeam as gap-filler for the nadir data. In sea ice, you can forget everything you think you know about surveying in open water. Whereas you would normally keep a short range and stay directly above the AUV, we just had to accept we were going to drift and have a very high horizontal range. This was intensified in the Weddell Sea by the ocean current phenomenon called the Weddell Gyre, which causes the ice to drift clockwise in a huge circular motion. On site, we experienced drift speeds from 0.1 to 1 knots. That’s why we chose the Sonardyne USBL tracking system in low-frequency (LF) mode because we wanted to extend the slant range detection, giving us a horizontal range of up to 11km away from the vessel.

Assuming that we successfully located the wreck, we also needed to document it, which would mean converting the Sabertooth into inspection mode. For this, we had on board an ultra-high-resolution laser scanning and photogrammetry system able to produce a 3D digital twin of the wreck with an incredible 1mm resolution. This had been specially developed in close collaboration with Voyis Imaging and McGill University in Montreal, Canada. To be able to zoom in on details, this was supplemented by a 4K broadcast camera from Deepsea Power and Light in the USA.

Which operational challenges did you anticipate in the Weddell Sea?

In another parallel with Shackleton himself – who referred to the ice as his “chief anxiety” – I realized that the main challenge would be the ice. In fact, FMHT were concerned that the SA Agulhas II might not even be able to reach the search box due to the ice conditions. Therefore, as a backup solution, we engineered a full-scale portable ice camp solution. Because all the personnel, equipment and consumables – weighing more than 40 tons in total! – had to be deployable by helicopter, no item was allowed to weigh more than 1.5 tons. Even the operations room, measuring 2.7mx2.1m, was small enough to be airlifted. As part of this backup plan, we built a sled-mounted launch and recovery system for the AUV that could be pulled across the ice, and we even invented a hydraulic drill auger capable of boring a 3m-wide hole in up to 5m-thick sea ice if necessary. In September 2021, we started training the crew how to deploy and disassemble the ice camp quickly – at a plastic ice rink, in fact – and we generated a 15m³ ice cube so they could practice using the drill.

We realized the ice drift due to the Gyre would be another huge challenge. Firstly, it would be important to manoeuvre our vessel into the right position before each dive; we would need to ‘park’ on the right side of the search box and drift over the wreck site, so to speak. And while the AUV was underwater for a dive, for many hours at a time, the sea ice motion would constantly change the vessel’s position on the surface. To anticipate this, we needed a reliable forecast of the pack ice in the Weddell Sea. Therefore, during the preparation phase, our expedition leader Dr John Shears worked with the German company Drift+Noise Polar Services to develop the state-of-the-art PRIIMA forecast system. By combining near-real-time satellite radar images with a mathematical wind and ice drift model, this gave us an updated 72-hour forecast every six hours. This, combined with our ability to constantly update the ROV with our current location so that it knew where to resurface, was absolutely crucial.

Once you arrived in Antarctica, how did the reality measure up to your expectations? And how did you solve unforeseen problems?

Even though we had spent years working on the planning and preparation, once we got on site everything was different. But we knew it would be – that’s why it was decided that I should be on board for the expedition, to be able to modify procedures in line with the ever-changing situation without losing valuable time. On all missions, I like to have a Plan 1, Plan 2 and so on rather than a Plan A, Plan B and so on, because then you’re limited to just 26 plans and associated solutions. I think we were already at Plan 125 when we arrived at the search location, and we made many more changes in the days after arrival!

No matter how much training you do, you’re never prepared for the actual climate conditions in Antarctica. Even though we arrive there in the summer, by the end of the project the water temperature was minus 1.8⁰C, the air temperature dropped to minus 14⁰C and the wind chill could be minus 25⁰C. The whole crew were tremendous. Working round the clock in 12-hours-on, 12-hours-off shifts was tough, and especially the people working on the back deck really suffered a lot, but they didn’t complain. I suppose history gave us all a sense of perspective; unlike Shackleton and his crew a hundred years earlier, we at least had hot food, dry beds and warm high-tech clothing!

The freezing conditions were also a challenge for the equipment and we had a number of technical issues. In particular, we suffered a charge issue with the batteries powering the Sabertooth and were obliged to speed up the process to launch charge after arrival on deck. We eventually realized that both our winches – prototypes built especially for the mission – were exerting too much tension on the cable. Call it foresight, but a few months earlier at the Saab Test Centre I had spotted a 20-year-old winch lying around that had previously been used by the Finnish navy. I always have a few reservations about prototypes, so I had arranged for the old winch to be brought along as an emergency back-up. When we tried that instead, the Finnish winch produced much less tension on the tether and also reduced the pullback on the AUV, which immediately improved the battery endurance. And because we didn’t actually need to deploy the ice camp solution, we erected one of the tents on deck and added a heater to shelter the equipment from the elements.

Given the time constraints, how did you optimize the efficiency of the search?

With a search box of roughly 120nmi² (420km²), the search area was relatively small by normal standards – the HUGIN could probably have covered it in a single run in normal open-sea conditions. But despite the excellent forecasting model we were using, we never knew exactly where we would end up – we were drifting at speeds of up to one knot sometimes. So we had to work really hard to ensure 100% coverage with no gaps and reasonable overlap. After a few days, we decided to work with the ice rather than against it. We subdivided the search box into 70 smaller sub-boxes that could be covered more easily within each six-hour forecast. Based on the weather and drift predictions, and thanks to the amazing technical skills of everyone on board, we could position the vessel to maximize the AUV’s dive efficiency each time.

After a few days of surveying, on 20 February, we thought we had found the wreck, but it turned out to be just a debris field according to the archaeologist and director of exploration, Mensun Bound. That was disappointing, but also slightly encouraging because I thought it meant the actual wreck could be close by. But then the days ticked by with no success. We were given a ten-day extension, but weather conditions were worsening and time was running out. Then after 20 days and 30 dives, when we had covered 81% of the search box, we finally found Endurance.

What happened when the wreck was finally found?

I was called into the control room at 4:05pm on 5 March when low-frequency sonar feed of debris had been picked up on the screen. Switching to the high-frequency sonar left no doubt that it was Endurance. The seabed was perfectly flat and uniform, so seeing the wreck was like seeing an oasis in the desert.

Despite the perfect sonar images, I wanted to see wood. Batteries were running low but we conducted another pass, this time with the camera switched on, moving from the port-side midship over the top, then turning to go to the bow. Then the batteries ran out and we had to do an emergency ascent vehicle recovery procedure. But it had allowed us to confirm 100% that we had found the full vessel.

After three years of work, to suddenly see her in front of my eyes, I was of course very excited. But I had to keep a cool head; we had just two days of the expedition left and we still had the whole inspection to do. So after allowing everyone to celebrate for about two minutes, it was time to get back to work. In training, the Sabertooth changeover from survey mode to inspection and laser scanning mode had taken 36 hours. In reality, I guess due to adrenalin, the crew did it in just 13 hours. This meant we were ready to dive again on the next day, which allowed us to complete two inspection dives.

Although we only got to spend eight hours with the wreck in total, it allowed us to capture over 25,000 high-resolution images. And they revealed that the wreck is amazingly well preserved, with a huge volume of artefacts visible. I’ve found several wooden shipwrecks in my career and usually nothing above the seabed survives the effects of sea life. But Endurance looks like it sank just yesterday. It’s magnificent and amazing, exceeding everyone’s expectations.

How is the success of Endurance22 helping to advance knowledge and understanding?

Although Endurance has been found, she is protected under the international Antarctic Treaty, meaning the site cannot be damaged, removed or destroyed, so the wreck will remain undisturbed. This, in combination with the challenges associated with reaching the location, means that the digital twin of the wreck – built using our 25,000 high-resolution images – is an extremely valuable resource for future research and education. For example, it is being used as input for an archaeological report currently being produced by the Falklands Maritime Heritage Trust, and it can also be used for many other purposes, such as by marine biologists studying sea life.

Information gathered during the expedition is also being used in a broader context. For example, data collected by the scientists working on the ice above Endurance can help in the study of climate change. Meanwhile, at Stellenbosch University in Cape Town, they are analysing the vessel’s performance during the expedition as the basis for building future ice breakers.

Additionally, to bring Shackleton’s story to a new generation through education and outreach, some 33,000 of schoolchildren across the globe were following our mission through the online Reach the World project. It’s amazing that the kids got so involved, interested and excited – on the day of the discovery, many of them even cheered “We’ve found Endurance” rather than “They’ve found Endurance”, and we got ten million impressions on TikTok.

I believe we need more exploration in this world and less conflict, so it really is an honour to have been part of this story and to inspire the future generation in this way. I’ve also been touched by the magic of Antarctica and can’t wait to go back – which is ironic, because having grown up in the French Alps, I hated the snow. In fact, that’s mainly why I studied hydrography when I was 18, so I could ‘escape’ to warmer climates and swim with dolphins! But above all, of course, it was a great honour to follow in the footsteps of Shackleton himself.

How does Shackleton serve as an inspiration for you, and how can his story inspire the hydrographic community in general?

I think two quotes from Shackleton sum this up perfectly. The first is “Difficulties are just things to overcome.” We were part of a huge challenge to do something that had never been done before, in the ‘worst place in the world’ in terms of remoteness and weather conditions, and under immense time pressure. To overcome such difficulties, we had to throw out everything we thought we knew and focus on what worked efficiently in that situation. And just as team spirt was key to the survival of Shackleton’s crew, teamwork was absolutely key to our success in solving the challenges we faced. You can’t work alone; each team member in the group supported the project, and I don’t just mean the 15 members of the subsea team, but also all 65 expedition members and 45 crew members – and not forgetting our dedicated person ashore, who really worked without stopping.

Shackleton’s second quote, which I think is particularly relevant for the hydrographic community, is “I believe it is in our nature to explore, to reach out into the unknown. The only true failure would be not to explore at all.” Let’s remember, despite the Seabed2030 project, much of the Earth’s ocean floor has still not been surveyed. Technology is advancing extremely fast with new types of sensors being developed and new vehicles that can survey at much deeper depths. We’re entering a new era for subsea survey, and access to new and more efficient technologies can create opportunities for exploration, which is good for mankind. Let’s work together to use tech to open up the world.

About Ernest Shackleton and Endurance

On 1 August 1914, Ernest Shackleton and his crew set sail from London on the 44m-long Endurance, one of the strongest wooden ships of that time, with the aim of crossing Antarctica on foot. Before even reaching mainland Antarctica, the vessel became trapped in the thick pack ice in the Weddell Sea on 18 January 1915. The crew had no choice but to sit it out and wait for the ice to thaw at the end of the winter. Despite the harsh sub-zero conditions, Shackleton succeeded in keeping everyone’s spirits high day after day. But as the months passed, the relentless force of the ever-shifting ice gradually crushed Endurance, forcing the crew to abandon ship on 27 October. She eventually sank on 21 November 1915. Determined that he and his crew would get out alive, Shackleton showed perseverance, leadership and inventiveness as he embarked on a superhuman journey of survival including a trek across the ice followed by a 1,300km voyage in small wooden lifeboats. Despite the failure of the expedition, Shackleton’s story is regarded one of history’s most epic tales of triumph in the face of adversity. He died of a heart attack during a subsequent expedition to Antarctica. He was buried on the island of South Georgia on 5 March 1922.

About Endurance22

Organized and funded by the Falklands Maritime Heritage Trust (FMHT), the Endurance22 expedition brought together world-leading marine archaeologists, engineers, technicians and sea-ice scientists on a mission to find the wreck of Sir Ernest Shackleton’s ship Endurance, which was trapped and crushed by the ice and sank in the Weddell Sea in 1915. On 5 February 2022, the team left Cape Town on SA Agulhas II, one of the largest and most modern polar research vessels in the world. The 132m-long, 22m-wide ice breaker weighs 11,700 tonnes, is powered by four diesel-electric generators each providing 4,000 horsepower, and cost US$127 million to build in 2012. Despite the harsh conditions, including freezing temperatures and heavy sea ice, the wreck was successfully located on 5 March 2022, and subsequently surveyed and filmed. On the voyage home, SA Agulhas II made an unscheduled stop at South Georgia to allow the team to pay their respects at Shackleton’s grave.

About Nicolas Vincent

Nico Vincent is a subsea engineer, surveyor and underwater vehicle manager with more than 30 years of experience on deep-sea projects. Today, Vincent is recognized as the ‘special project maker’ for deep-sea missions around the world. Just some of the notable projects he and his team have been involved in include the recovery of the world’s deepest cargo of silver coins from the wreck of SS City of Cairo, the location of the fighter plane of Antoine de Saint-Exupéry, and discovery of the world’s deepest wreck: the USS Samuel B. Roberts (at 6,895m depth) in the Philippine Sea. They have also located the missing naval submarines AJA San Juan and La Minerve, and helped investigate significant air accidents, including Air France AF447 in 2009, Malaysia Airlines Flight MH370 in 2014 and EgyptAir Flight MS804 in 2022. Following the failure of the unsuccessful expedition to find Endurance in 2019, Vincent worked for over three years non-stop to plan Endurance22. He is a member of the Society of Underwater Technology, la Société des Explorateur Français, and The Explorer Club, who awarded him on behalf of the Endurance22 team their prestigious Citation of Merit in 2024 for the discovery of Endurance. Vincent is now the operations manager of Deep Ocean Search Ltd.

More information

https:/fmht.co.uk/shackletons-endurance-revealed/

Book: Endurance: The Discovery of Shackleton’s Legendary Ship, John Shears and Nico Vincent, National Geographic Partners, ISBN 978-1-4262-2383-9

Documentary: ‘Endurance’, https://films.nationalgeographic.com/endurance#watch-the-trailer