presented by Science@NASA

Flying low and slow

above the pristine terrain of Alaska's North Slope

research scientist Charles Miller

of NASA's Jet Propulsion Laboratory

surveys the white expanse of tundra

and permafrost below.

On the horizon a long dark line appears.

His plane draws nearer

and the mysterious object reveals itself to be a massive herd

of migrating caribou

stretching for miles.

It's a sight Miller won't soon forget.

'Seeing those caribou

marching single-file across the tundra

puts what we're doing here in the Arctic into perspective' says Miller

who is on a five-year mission named 'CARVE'

to study how climate change is affecting the Arctic's carbon cycle.

CARVE is short

for the 'Carbon in Arctic Reservoirs Vulnerability Experiment.'

Now in its third year

the airborne campaign is testing the hypothesis that

Arctic carbon reservoirs are vulnerable to warming

while delivering the first source-maps of greenhouse gases

carbon dioxide

and methane.

About two dozen scientists

from 12 institutions are participating.

'The Arctic is critical to understanding global climate' says Miller.

'Climate change is already happening in the Arctic

faster than its ecosystems can adapt.

Looking at the Arctic

is like looking at the canary in the coal mine

for the entire Earth system.'

Over hundreds of millennia

arctic permafrost soils have accumulated vast stores of organic carbon -

an estimated 1400 to 1850 billion metric tons of it.

That's about half of all the estimated organic carbon

stored in Earth's soils.

In comparison

about 350 billion metric tons of carbon

have been emitted from all fossil-fuel combustion

and human activities since 1850.

Most of the Arctic's sequestered carbon

is located in thaw-vulnerable topsoils

within 3 meters of the surface.

But as scientists are learning

permafrost - and its stored carbon -

may not be as permanent as its name implies.

And that has them concerned.

'Permafrost soils are warming even faster than Arctic air temperatures -

as much as 1.5 to 2.5 degrees Celsius

in just the past 30 years' says Miller.

'As heat from Earth's surface penetrates into permafrost

it stimulates soil processes

that mobilize these organic carbon reservoirs

and release them into the atmosphere

as carbon dioxide and methane

upsetting the Arctic's carbon balance

and greatly exacerbating global warming.'

CARVE campaign flights

are conducted aboard a specially instrumented NASA C-23 Sherpa aircraft

from NASA's Wallops Flight Facility

on Wallops Island in Virginia.

The C-23 won't win any beauty contests -

its pilots refer to it as

'a UPS truck with a bad nose job.'

Inside it's extremely noisy -

the pilots and crew wear noise-cancelling headphones to communicate.

'When you take the headphones off

it's like being at a NASCAR race' Miller quipped.

But what the C-23 lacks in beauty and quiet

it makes up for in reliability

and its ability to fly 'down in the mud.'

Most of the time

it flies about 150 meters above ground level

with periodic ascents to higher altitudes

to collect background data.

Onboard the plane

sophisticated instruments sniff the atmosphere for greenhouse gases.

[We] need to fly very close to the surface in the Arctic

to capture the interesting exchanges of carbon

taking place between Earth's surface and atmosphere' Miller says.

The CARVE team flew test flights in 2011

and science flights in 2012.

So far in 2013

they have completed three monthly campaigns-

in April May and June-

with four more to go.

From a base in Fairbanks Alaska

the C-23 flies up to eight hours a day

to sites on Alaska North Slope

interior and Yukon River Valley over tundra

permafrost boreal forests peatlands and wetlands.

Soaring over the Arctic terrain

Miller has seen many things he won't forget.

Like the Caribou

the data may prove unforgettable too.

For more news from the ends of the Earth-and-beyonds-

visit science.nasa.gov