CFB SHEARWATER, NOVA SCOTIA—From the desert badlands of Afghanistan to the frigid depths of the High Arctic, Royal Canadian Navy divers are tasked with some of the toughest missions troops can face.

The next big operation for members of Fleet Diving Unit Atlantic, the Royal Canadian Navy’s East Coast dive team, is to help Parks Canada archeologists explore the sunken wreck of HMS Erebus.

She was Sir John Franklin’s flagship in his doomed 1845 attempt to complete the Northwest Passage through the maze of islands and channels in Canada’s Arctic Archipelago.

The navy divers routinely take on the traumatic job of recovering the remains of air crash victims, suicides and others taken by the sea. Some of the unit’s sailors have spilled their own blood in southern Afghanistan.

But their planned 11-day mission to help reveal the secrets that Erebus has held for close to 170 years is likely to draw more world attention than the quietly courageous navy divers have ever had.

Civilian marine archeologists who got a look at the shipwreck after it was discovered last September won’t say what they expect to find during the April operation.

What they know from last year’s dives and video captured from a remotely operated vehicle is a closely guarded secret.

But the hurry to get back to Erebus, working from a camp on sea ice in a fierce Arctic winter, suggests they expect her to give up some significant clues to help solve the mystery of why Franklin and his 128 men died.

Archeologists say the wreck site is rich with artifacts that will take years to catalogue and study.

Despite the higher risk of diving under ice, they’re in a hurry to get back to Erebus to search for significant finds — perhaps even the captain’s logbook or human remains — before they suffer more damage from the elements or looters.

Navy divers train hard for the unique hazards of working under ice. Getting to the surface in an emergency can be difficult if divers get tangled up in air hoses, or they can’t reach their exit hole in the ice for some other reason.

It’s called “confined space diving” and the shipwreck site adds another complication: the divers will be working in water below freezing, where they can be buffeted by ocean currents.

The sailors have been teaching ice diving skills to Parks Canada’s underwater archeologists for weeks, while learning from them how to avoid damaging Erebus or the artifacts that are crucial to understanding what happened to her and the expedition.

“At all times, it is the intent that a military diver and a Parks Canada diver will be in the water together,” Chief Petty Officer 2nd Class Larry Lyver, 50, of St. John’s, N.L., told the Star. His partner in the complex operation is Lt. Greg Oikle, 38, of Dartmouth, N.S.

As operations chief, Lyver is in charge of setting up and running the divers’ ice camp in eastern Queen Maud Gulf, and for making sure they get their work done safely.

Working with the military’s Arctic logistics hub, Joint Task Force North in Yellowknife, Lyver has laid plans to feed and house more than 50 people. Around two dozen of those are expected to be Parks Canada marine archeologists and navy divers.

Inuit Rangers will be there to deter hungry polar bears and offer experience on surviving the brutal Arctic winter, when gales and blizzards can hit from the North Pole like a sledgehammer.

To reach Erebus, the mission team will cut a hole through the sea ice, planned as a triangle with each side just under two metres long. Lyver expects the ice to be anywhere from two to three metres thick.

The search for Franklin

They’ll use a hot water drill — a gas-fired unit less than two metres long — developed by Defence Research and Development Canada.

A hole drilled through the ice near Erebus with an augur will supply water, which is heated in a system of coils to around 75C.

It passes through tiny holes drilled in copper tubing, and the steady drip of steaming hot water slices a straight cut through the ice. The crew will haul up the heavy ice in pieces to clear their portal to Erebus.

Divers will then go down in pairs. Their air supply will come through hoses running from compressors on the surface. A communications cable completes each diver’s tether.

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The team exploring Erebus won’t have the luxury of special suits that are warmed with hot water pumped from above. The navy has them, but Lyver doesn’t see any need on this operation.

So the divers will have to tough it out in thermal underwear and cotton gloves under triple-layered or neoprene dry suits, working in shifts of roughly 50 minutes.

Some of the most monotonous hours of their underwater time, during work days expected to run 12 hours or more, will be spent carefully trimming thick kelp beds that have overgrown Erebus. That will give archeologists a clearer look at her.

The divers will be cold, especially their hands. Moving fingers, holding onto a tool, can quickly become a chore on ice dives, at which point it’s time for a shift change. Too much protection against the cold makes it harder to work. So divers end up shrugging off the pain.

“There are a lot of old divers around with creaky fingers from diving the old way,” Lyver said. “Arthritis has a tendency to be your buddy.”

For Canadian Navy divers, so is trauma.

Several in the Atlantic unit are still living with the nightmares of Swiss Air Flight 111.

Soon after 10:31 p.m., when the McDonnell Douglas MD-11 bound for Geneva from New York crashed into the Atlantic Ocean on Sept. 2, 1998, the dive team’s beepers and phones started ringing.

All passengers and crew died in the crash. The Atlantic fleet’s divers worked for weeks in the waters near Peggy’s Cove, N.S., retrieving remains, mostly body parts, of the passengers and crew.

Navy divers also did front-line duty in the deserts of southern Afghanistan, where their skills in defusing bombs were central to the fight against Taliban-led insurgents.

The only Canadian sailor killed in action in Afghanistan is memorialized on the wall of honour in the unit’s headquarters.

Petty Officer 2nd Class Douglas Craig Blake, 37, of Simcoe, Ont., was a navy clearance diver. His specialty was defusing explosives, underwater or on land.

Blake had successfully defused at least two improvised explosive devices, the Afghan insurgents’ most effective weapons against Canadian and allied forces, the citation reads.

Then, on the afternoon of May 3, 2010, Blake and his team disposed of an IED and were returning to their vehicle when a bomb exploded.

The blast in Panjwai District, a notorious Taliban stronghold southwest of Kandahar City, killed Blake. True to an old navy tradition, he was buried at sea on May 14, 2010.

The navy divers who will descend on Erebus, the first sailors to touch the Royal Navy ship since her brave crew perished, are driven by the same conviction that they have an important mission to complete.

“We’re there to work,” Lyver said. “It’s not ‘two dives a day and high fives all around.’ All the information, everything the world is hoping to see, absolutely depends on the success of what we can do. So it’s, ‘As much as it takes, as long as it’s safe.’”