By Richard Black Environment correspondent, BBC News website, Alaska

Air temperature readings were taken manually in the old days

Science can be a lonely business.

"Sometimes you'd just land and set up your equipment," recalls Carl Benson, "and the pilot sees clouds rolling in and says 'I'd better get out of here, do you want to come with me or do you want to stay'?

"So you push the 'plane round so they can take off, and you don't know when you're going to see them again."

Dr Benson is one of a band of scientists hardier than most who have spent decades working to understand the finer workings of glaciers.

Here in Alaska, the distances are so big and human settlements so rare that flying to work in a tiny chartered aeroplane is just about the only way to do it.

There is one glacier that has proved irresistible to two generations of Alaskan glaciologists - the McCall Glacier in the far northeast, in the Brooks Range on what is termed the North Slope.

I nearly went down a crevasse once on a snowmobile; I was on my own, I was absolutely scared Gerd Wendler

It is close to the Arctic Ocean; but, importantly, it ends well short of the coastline.

The McCall is one of a handful of North American glaciers with a scientific history going back half a century. And at a time when glaciers are widely seen as canaries in the climate coalmine, the foresight of Dr Benson's forebears in setting up research bases there is proving something to applaud.

Looking back

The McCall came into scientific reckoning in 1957, when scientists were looking for glaciers to study as part of International Geophysical Year (IGY), also known as the third International Polar Year (IPY).

"The McCall is a better place to look than coastal glaciers, because there the ice goes into tidewater and signs of changes in the glacier can be masked by changes at the coast," says Gerd Wendler.

I encounter Drs Wendler and Benson and other McCall researchers at the University of Alaska at Fairbanks (UAF) in the middle of the state.

This year and next mark the fourth IPY, an apt time for the McCall pioneers to look back on what it has taught them, and how conditions for research have changed over half a century.

The lead scientist on the original IPY project, Dick Hubley, committed suicide on the glacier just as his research was getting into full swing.

But Carl Benson and Gerd Wendler's involvement dates back to the late 1960s, and as always in science, lore and legend as well as facts and figures have passed down the generations.

Air supply

Dick Hubley's IPY team intended to over-winter at the glacier, something that has not been attempted since.

Instead, teams arrive in the spring and leave in the autumn, usually by plane, with air drops augmenting the equipment travelling with the research team.

You're operating in marginal conditions, and there's huge pressure on the pilot Dennis Trabant

"We didn't have good electronics, so you had to run a generator for two hours to charge a battery bank in order to run the instrumentation 24 hours a day," recounts Gerd Wendler.

"And the generator needs fuel, and that was air-dropped."

Food, including eggs, and other supplies would also arrive from the sky, though not always precisely where it was intended.

"It's a narrow glacier to drop parachutes on," says Keith Echelmeyer.

"There have been lots of near misses, and so you see lots of parachutes scattered around the place."

To compound matters, the early equipment did not always function as it should. Battery life was an important issue, with data recorders slowing down as the "juice" ran out.

Not all data collection could be automated anyway.

"Back then, data loggers were humans, not pieces of electronics, and every one or six hours they had to manually record weather observations," says UAF's Matt Nolan.

"Today I have electronics making measurements every minute automatically, and I can check the weather there while drinking my tea and writing emails in my pyjamas here in Fairbanks."

Profiling the top of the glacier has also changed hugely. In the 1950s it was done with theodolites and sticks; now satellites can provide reams of quick and reliable data.

Then there were the dangers of working in small groups, or even solo, in this inhospitable terrain

"I nearly went down a crevasse once on a snowmobile," recounts Gerd Wendler.

"I was on my own, I was absolutely scared."

Supplies, including food and fuel, would arrive by parachute

The assembled scientists all pick out the flights in and back, landing and taking off on the unprepared glacier itself, as the main hazard.

"You're operating in marginal conditions," says Dennis Trabant, a former US Geological Survey scientist.

"The pilots have customers that want to fly, they're sitting around in tents or motels they can't afford, or there are people who have a limited schedule, and maybe the weather's not very good but there's huge pressure on the pilot because he wants to please you and he wants to get your money."

Weather prediction may have improved since then, but the basics of getting in and back remain - the conditions will always remain something to be respected.

What's at stake?

The main scientific objective has always been to determine the glacier's mass balance - whether it is gaining or losing ice over time, whether the accumulating snowfall during the winter is more or less than the summertime melting.

The methodology is surprisingly straightforward - "rude and crude," as Matt Nolan labels it.

"You take a steam drill, bore a hole between three and nine metres in depth, and put in a stake - in fact we sometimes use pieces of electrical conduit.

"You measure how much of the stake is exposed when you put it in, then you go back at a later time and see whether more or less is now exposed."

And you do it all over the glacier, to take account of the different conditions at various altitudes, and combine the readings to derive a trend for the entire ice body.

In 1998, Professor Echelmeyer showed that the McCall had been shrinking ever since the first measurements were taken in 1957, and that the rate of loss had increased.

The glacier thinned each year between 1972 and 1993 by an average of 33cm. Subsequently, the rate nearly doubled.

The McCall's snout receded significantly between 1958 and 2003

"I think another key thing is the equilibrium line - the line dividing the upper accumulation zone, where more snow falls than melts, and the lower ablation zone, where more melts than falls," says Dr Nolan.

"Over the last 50 years, it's increased in elevation to the point at which in some years it's higher than the top of the glacier itself, so in some years there's no accumulation."

The McCall is signalling clearly that the local climate is changing, and a significant Alaskan temperature rise in the mid-1970s has been well documented.

But how much that is down to natural cycles, the Arctic Oscillation and the Pacific Decadal Oscillation, and how much to rising greenhouse gas levels is a matter for some discussion, complicated by the fact that Alaska contains three distinct climatic regions.

"The last three decades in Alaska are some of the warmest on record," says Gerd Wendler, "but over those three decades there has been absolutely no temperature increase whatsoever except in the North Slope.

"The warmest temperature ever recorded in Fairbanks dates back to 1926."

Another half century?

The details of the McCall have intrigued researchers since study began here half a century ago.

Matt Nolan shows son Turner how science is done on the McCall

It is a polythermal glacier - the temperature varies from 0C down to what Matt Nolan terms "very cold".

Water percolates down through the upper levels, lubricating the ice flow. And beyond the snout, runoff water accumulates and freezes again - aufeis, as it is called - and unusually, it persists through the summer.

But for how much longer will the glacier itself endure the summers, if North Slope temperatures continue to rise? Assuming there is another IPY in 50 years' time, will there be anything left of the McCall for the next generation of glaciologists to study?

"If things continue on the same trend - and we don't know whether that will happen or not - I'd say it's within the realm of possibility that the bulk of the glacier will be gone in 50 years," is Matt Nolan's assessment.

Which would be a shame, given the long history of science on the McCall, and what it has told successive generations of glaciologists about the workings of glaciers and about climate change in this corner of the Arctic.

Richard.Black-INTERNET@bbc.co.uk