A three-year global mountaineering quest has ended in tragedy for an Australian couple after one slipped and fell to her death while climbing in Fiordland.

Melissa Therese Martin and her fiance Brad Skinner had left their jobs and waved goodbye to Sydney with the goal of conquering mountains around the world.

That dream ended on Wednesday when Ms Martin, a 38-year-old IT project manager, slipped and fell to her death.

Crossing four continents, their expedition was also to double as a bio-medical research project for a University of Technology Sydney experiment.

The aim was to measure heart-rate variability, or variations of their heart rates over time, during several "unsupported lightweight mountaineering and trekking exploits in remote alpine environments".

The couple of 15 years blogged their plans and pursuits during what they christened "Adventureneering 2011-201?"

The pair planned to base themselves in Queenstown, Wanaka and Te Anau for three months before tackling Asia, Europe, Africa and the Americas.

In a story about their expedition on the university website, Ms Martin expressed her love of the outdoors: "I prefer the long, alpine traverse. You feel so great after you've been out walking for weeks; you really feel like Superman. It's awesome."

But it was a trip that would never reach the global peaks that were intended.

While climbing in the Korako Glacier area, near Lake Adelaide, in Fiordland, it is believed Ms Martin lost her footing and plummeted to her death.

Sergeant Tod Hollebon, of Te Anau, said the couple were roped together when Ms Martin fell and during her descent she took her partner Mr Skinner with her.

It was not known at what stage during the fall Ms Martin died, Mr Hollebon said.

Mr Skinner was presumably rendered unconscious and it was not known how long it was before he awoke and activated his emergency beacon, he said.

The couple were found by a Southern Lakes Helicopter crew.

Its operations manager and winchman Lloyd Matheson said it had taken the helicopter team about 45 minutes to locate the couple.

The terrain was sheer, he said, and the pair were wearing dark clothing so they were "camouflaged" in the ice.

Mr Skinner suffered non-life-threatening injuries, including damage to his face, and remains at Te Anau for medical treatment.

Mr Hollebon said Mr Skinner had been left "completely devastated and distraught" by the incident.

Early indications were that the couple were well-equipped and attempting a climb what was well within their "range of ability".