Expedition Endurance22 (1): The most difficult to locate ship on earth

"This journey into the unknown is a unique undertaking because we are looking for the most difficult to locate ship on earth," explains Lasse Rabenstein, chief scientist of the Endurance22 expedition, "there is no guarantee of success." It is February 5, 2022. The geophysicist Rabenstein sets sail from Cape Town with polar explorers, archaeologists and engineers, at that time still in summer clothes.

On the Agulhas II, explorers head southwest to find Ernest Shackleton's lost ship, which sank more than a hundred years ago on the last major expedition of the golden age of Antarctic exploration.

Rabenstein and his team regularly send messages from the Agulhas II.

Ernest Shackleton set out on the Endurance in 1914 to be the first to cross the continent across the geographic South Pole.

The three-masted tall ship with a steam engine had been designed for polar conditions, and the Endurance could have sailed through loose pack ice.

But in January 1915 she was completely surrounded by pack ice in the Weddell Sea and finally crushed by ice masses after 281 days.

She sank to a depth of 3000 meters and became as famous as Shackleton's adventurous rescue operation, which ultimately saved all expedition members from death.

Almost a hundred years later, the private foundation Falklands Maritime Heritage Trust decided to find the wreck and initiated a first search expedition in 2019, which, however, failed: The heart of that search,

an Autonomous Underwater Vehicle (AUV) for unmanned diving, was lost under the closed ice sheet.

The team returned disappointed but with some lessons learned.

Prevent repeated data loss

Now you would be prepared for such a case.

"To ensure that the information collected is not lost in the event of an AUV loss, the new AUV sends all measurement data to the deck in real time," explains Rabenstein.

On board is an international team of underwater robotics and sea ice experts, including colleagues from the Alfred Wegener Institute (AWI) and the German Aerospace Center (DLR), who are pursuing other research projects in the Weddell Sea.

But before the AUV can be used, they must first reach the spot where endurance is believed to have dropped, according to historical records.

The overwhelming force of colliding masses of ice was not only feared in Shackleton's time.

Today, however, in addition to more stable icebreakers, there are also modern forecasting methods.

Rabenstein's four-person ice monitoring team from Drift + Noise Polar Services, an AWI spin-off, continuously evaluates satellite data on board the Agulhas II together with DLR.

Radar measurements can be used to determine sea ice concentrations through clouds.

This data is combined with weather models to predict ice movement.

The drift directions of the ice sheets change constantly and quickly: sea routes in the form of cracks in the ice open and close temporarily like in a moving labyrinth.

It is also Rabenstein's task to find the best possible path through the ice — or, if that is hopeless,

Prepared for an early winter

There are many uncertainties, Rabenstein points out on the sixth day of the crossing to the Weddell Sea.

For example, the Agulhas II is not a nuclear-powered nuclear icebreaker of the highest possible ice classification "Polar Class 1".

The ship is only polar class 5 and cannot easily navigate three meters of ice.

If winter came too quickly at the South Pole, things could get tight, but such eventualities have been taken into account: "If we can only get within 40 nautical miles of the wreck coordinates, plan B will come into play: Two helicopters would bring the five-meter-high drilling rig onto a selected ice floe that drifting across the coordinates at the right time.

The drilling company would have to drill a hole for the AUV use there,” says Rabenstein.

Fortunately, when the Endurance 22 expedition reached the study area on February 16, the ice conditions were still easy.

The AUV has been diving for the wreck since Friday, and the excitement is growing.

Only the penguins and seals are currently lounging on the floe.

"It's the first important milestone to have arrived at all," says Rabenstein before he disembarks with his AWI colleagues in polar gear.

The scientific activities on board that he coordinates are also starting now, parallel to the search for the wreck.

We will keep reporting here on the current status of the expedition in the coming weeks.