Police have postponed the mission to recover a body from Fox Glacier.

The police operation to examine and recover the human remains discovered on Fox Glacier has been postponed for the day after clouds closed in, Sergeant Mathew Tailby said.

"Today police travelled to Fox to undertake the recovery, however the deterioration in weather conditions has made it unsafe to fly to the Glacier.

"We will now continue to reassess the weather over the next few days, but it is not believed conditions will be suitable to access the Glacier site before Monday.

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"Once we can get to the scene a post mortem will be required to identify the remains as they have been there for some time.

"Once identified, police's first priority will be notifying their next of kin."

A tramper discovered the body in a crevasse near Chancellor Hut about 10.30 this morning and contacted police.

Greymouth Sergeant Paul Watson told Fairfax the body found may have been involved in an historic incident.

"It has possibly been up on the ice for a considerable time and only found now because of changing conditions."

He told Fairfax police would be reviewing files of missing people in that area from 30 years ago or more.

He said the body was found with a backpack, which may help to identify the person.

Police are now heading to the glacier to find out who the person is and notify next of kin.

Glaciologist Andrew Mackintosh said the fact the body was found in a crevasse led him to believe it might have only been there for a few years.

"When something like a body or, I don't know, an aircraft falls into the top part of the glacier, it goes on a journey into the ice and reveals itself down near the bottom some time later," he said.

Items moved through the ice in some glaciers faster than in other glaciers, so for a body moving through the ice at Fox Glacier, it would likely only take one or two decades to emerge, he said.

A different glacier, such as Tasman Glacier, might move an item through the ice over several hundred years.

Mackintosh said crevasses, on the other hand, usually opened up for a few years at a time and then closed again, so he did not believe the body would have been there for 30 years or more.

"If a body turns up in a crevasse, my guess would be that it's actually relatively recent," he said.

"My gut feeling would be that it's just sort of been in the last five years."

If that was the case, he said the body was likely fairly decomposed, and likely was in there due to the person falling into the crevasse.

Mackintosh did not believe receding glaciers meant bodies might turn up more often, as the fact they were receding did not make much difference to the speed a body moved through the ice.

"I don't really expect any great change there," he said.

Glaciers Country tourism group chairman Rob Jewell was unaware of the discovery of the body.

"In fact, I have been here for 10 years and don't recall anyone going missing in that area," Mr Jewell said.

Both the Fox Glacier and its northern twin Franz Josef Glacier have given up bodies and debris in the past. In 2010, glacier guides found items discarded during renovations to the Chancellor Hut in the 1950s emerging from the glacier terminal.

At the time guide Marius Bron discovered scraps of orange-painted corrugated iron, which were believed to be from the chimney repairs made 50 years earlier, having been thrown off the cliff onto the glacier below.

"It's not conclusive, but there's a chance that's it. It's right on the edge of the glacier, so there is a good bit of friction along the side it would have rumbled down," Mr Bron said.

Human remains expert John Dennison said the body could be in any condition, from perfectly preserved to deformed from the pressure of the ice.

Dennison once examined a single bone discovered at Fox Glacier, and said while the bone could have been there for any time up to 10 years, he was able to find residual hair and tissue on it and determine the bone was from a young, fair-haired male.

"The bone itself was slightly misshapen because the ice pressure had distorted the bone," he said.

Dennison said investigators would need "a very wide net" to discover when the body was from, "and then narrow it down from there".

The ice and any lack of oxygen could preserve the body "in the state in which it had gone down there, but the body also might not have been preserved". Without more information it was too hard to tell what state the remains would be in, he said.

- Additional reporting by Greymouth Star