by Anil Ananthaswamy
09 December 2015

from NewScientist Website

Downloaded from Scribd Website

A hidden land of lakes, rivers, volcanoes, and even life is changing our image of Earth's seventh continent forever.

At last we're glimpsing the pulsating landscape under Antarctica's frozen blanket, says Anil Ananthaswamy Antarctic ice sheet.

 

Their aim was to establish a base near the Pole of Inaccessibility, the furthest point on the continent from the Southern Ocean.

 

Thirty-two men struck out from the coast with the equipment that was left after a storm broke up the ice around their ship while they were unloading - sinking

It took three weeks of crossing frozen terrain to reach the lake, and five days to punch a hole through its icy lid.

When they finally broke through to the water below, the excitement was palpable. Hands grabbed the gooey mud pulled up through the hole.

For this was no ordinary ice-fishing expedition:

Slawek Tulaczyk and his team had drilled through 800 meters of ice into Antarctica's Lake Whillans.

The team's efforts - battling through 14-hour shifts in some of the harshest conditions on Earth - are part of a massive endeavor to uncover the continent's hidden secrets.

Over a century ago, explorers trudged across its white blanket in pursuit of world records, aware only of the snow, ice and treacherous weather.

But in the last few decades a different kind of explorer has started to peer beneath the ice, to discover what Jill Mikucki at the University of Tennessee in Knoxville describes as a sub-ice water-world.

Hidden landscapes
Beneath Antarctica's ice cap are huge mountains,

active volcanoes, hundreds of
lakes, rivers and even life

Their labor has revealed a pulsating continent with lakes, rivers, volcanoes, even life:

hardly the frozen wasteland of popular imagination.

In a way, the adventure began in 1957, when a ship carrying members of the third Soviet Antarctic expedition arrived at the East sledges and a tractor but no men.

At regular intervals along the way, they set off small explosives and recorded the echo of seismic waves as they travelled through the ice and bounced off whatever lay beneath. Near the centre of East Antarctica, the explorers found a region of anomalously thin ice.

They had stumbled across a massive mountain range beneath, its peaks reaching up towards their feet (see picture far below).

Almost 3000 meters high, the Gamburtsev mountain range has an Alpine topography, replete with rugged peaks and hanging valleys, yet it is completely hidden from view.
 

The Gamburtsev mountains,

seen on a radar image through hundreds of metres of ice

ANTARCTICA'S GAMBURTSEV PROVINCE PROJECT

The ice above is anywhere from a few hundred meters to 3.2 kilometers thick.

Then, during the late 1960s and early 1970s, planes equipped with ice-penetrating radar revealed bodies of water locked between the ice and the bedrock: lakes hundreds, sometimes thousands of meters beneath, and still liquid thanks to the immense pressure of the ice above and geothermal heat from below.

These were the days before GPS and its Russian equivalent GLONASS, and pilots had to keep the Russian Vostok research station in their sights or risk getting lost over the vast, white, featureless expanse.

So it was pure luck that beneath the station sat the continent's biggest lake:

Lake Vostok, seventh largest in the world by volume, fourth deepest and 3.7 kilometers under the ice.

Vostok - like Antarctica's other large lakes - sits in a depression in the bedrock and is "inactive":

it fills and drains very slowly.

But in recent years, teams studying other subglacial lakes have discovered a dynamic system of streams and even rivers that interconnects some of them.

Duncan Wingham of University College London and his team were the first to spot the massive movement of water beneath the ice.

In 2006, they showed how parts of the East Antarctic ice shelf rose and fell, as if the ice were breathing. When the ice sank in one location, a similarly abrupt rise was seen several hundred kilometers away.

They concluded that water was flowing from one set of buried lakes to another.

"That was quite a revelation," says Hugh Corr of the British Antarctic Survey (BAS).

At the last count, polar researchers have identified about 400 subglacial lakes in Antarctica (see map far below). The discovery has turned the image of a massive ice sheet grinding against the bedrock on its head.

Rather, there is an entire hydrological system between the ice and rock.

"Just how much water there is underneath has been a surprise," says Corr.

"The temperature under the ice

was extremely hot - Yellowstone hot"

 

There's fire down there, too.

During the 2004-05 Antarctic summer, a joint US-UK team carried out an airborne survey to take radar, magnetometer and gravity measurements near Pine Island glacier in West Antarctica.

They found something hundreds of meters beneath the ice surface that strongly reflected their radar signal. Hugh Corr and David Vaughan, also at BAS, analyzed the findings and concluded that the reflections were coming off a layer of ash and rocks, the remnants of a massive volcanic eruption.

The volcano, known as Mount Casertz, erupted about 2000 years ago, punching its way through the ice to spread debris over 26,000 square kilometers.

The explosion would have been on the scale of the 1980 blow-up of Mount St Helens in the US. Even today, the ice over Mount Casertz is depressed, suggesting heightened geothermal activity underneath.

And in 2010 and 2011, seismometers picked up the rumblings of another active volcano in West Antarctica.

It was against this backdrop of fire and ice that Tulaczyk, of the University of California in Santa Cruz, set out for Lake Whillans in West Antarctica.

In December 2012, an advance party of tractors - each dragging a chain of shipping containers mounted on sledges - had to cover the 800 kilometers separating the McMurdo research station from the lake.

The containers held nearly 500 tonnes of equipment. Designed to be stacked on ships, not pulled across undulating, wind-hardened ice and snow, they didn't travel well.

The crew had to keep welding fractured metal, sometimes cutting parts from one container to patch up another.

By the time the convoy reached the remote site and Tulaczyk and 60 more scientists had flown in from McMurdo, it was mid-January.

They had until the end of the month before temperatures would begin to fall. In that time they had to drill through 800 meters of ice to Lake Whillans, drop their instruments through the hole one by one, take measurements, gather samples, then pack everything up and head home.

Tulaczyk remembers the day they finally broke through and dredged up mud from the lake bed.

"People were grabbing the stuff as a souvenir," he says.

 

"After spending weeks and weeks surrounded by just snow, to have this very tactile, physical evidence that there is something else [besides] ice underneath our feet… It was so amazing for them."

One of the instruments dropped down the hole was a sensor to take the lake bed's temperature.

Until then, there had been only indirect hints that Antarctica's underbelly was warm.

"The measurement came out to be extremely hot - Yellowstone hot," says Tulaczyk.

Similar measurements have been taken at some 35,000 sites around the planet. Only 100 or so are hotter than the Whillans lake bed.

We don't yet know why West Antarctica is so hot and volcanic. It could be that the crust is thinning there.

As an analogy, Tulaczyk points to the area between the Sierra Nevada mountains in the western US and Salt Lake City in Utah:

over time, the two have moved apart, stretching the Earth's lithosphere and producing geothermal and volcanic activity. Or, paradoxically, the heat could be generated by the ice.

The West Antarctic ice sheet has grown and shrunk many times over the past few million years.

When the ice is thicker, it depresses the crust, which rebounds when the ice melts. As the crust bobs up and down, so does the viscous mantle 100 kilometers lower down.

This constant massaging of the mantle can release heat.

Falls, as the site is known, is the result of iron particles that oxidize in the sunlight. Inside the brine, Mikucki and colleagues have found evidence of "chemoautotrophic" bacteria that live in complete darkness - presumably beneath the Taylor glacier - by chemically leaching energy from the bedrock and producing iron as a by-product.

They don't rely on energy from the sun, not even in the indirect way that, say, fish at the bottom of the ocean do when they eat dead material that falls from the surface.

The team now want to find where the bacteria come from.

Blood Falls is a salty waterfall, and salty water conducts electricity better than freshwater. So earlier this year, Mikucki and her team went out to the area with instruments that can remotely measure electrical conductivity beneath the ice.

Blood Falls offers clues

to how life survives beneath the ice

USAP

They found large pockets of high conductivity beneath the Taylor glacier.

The researchers believe the sediments there are saturated with brine and could host the microbial ecosystems that flow out at Blood Falls.

Although soggy sediments that can support microbial life are definitely prized findings, the treasured goal for Antarctic researchers is to find life in liquid subglacial lakes.

Over the past decade Russian scientists have been drilling down to Lake Vostok.

The first time they broke through to it, in February 2012, the samples they brought back up to the surface were badly contaminated with the drilling fluid they used to keep the borehole open.

After colleagues in Grenoble, France, cleaned them to remove any trace of contaminants, the Russians found no conclusive signs of microbial life.

When they broke through to the lake a second time, in January this year, special care was taken to prevent contamination. But with their current drilling equipment, it's hard to avoid contamination entirely.

Any search for life under these conditions is bound to be inconclusive.

"We need clean water samples to make conclusions. We dream about it," says Irina Lekhina of the Arctic and Antarctic Research Institute in St Petersburg, Russia.

She would also like to have water from the main body of the lake.

At the minute, they are only sampling the very top layer, which rises into the borehole during the final phase of drilling.

"We believe that life, if it exists, will be deeper," says Lekhina.

Tulaczyk and his colleagues did get a sample of pristine water from Lake Whillans.
 

Admittedly, their task was easier, with far less ice to get through and warmer temperatures to contend with.

They didn't need to keep the borehole open with drilling fluid. Instead, they used a hot-water drill - collecting boiling snow at the surface, irradiating it with UV light to kill everything inside, and then pumping it down through the ice. The nozzle and other equipment were also irradiated and washed with hydrogen peroxide.

When the team broke through to Whillans on 27 January 2013, it was the first clean drilling into a subglacial lake, says Tulaczyk.
 

In the water samples they found plenty of evidence for a thriving microbial ecosystem.

DNA sequences suggest that the microbes in Lake Whillans are chemoautotrophs, like the ones at Blood Falls.

"They get their energy from rocks and mud and stuff underneath the ice," says team member Ross Powell of Northern Illinois University in DeKalb.

On 8 January this year, the team drilled at another location, downstream of the lake.

This time the borehole went through the Ross ice shelf, just above the glacier's grounding zone, where the ice lifts off the bedrock and begins floating on ocean water.

The researchers lowered a camera down into what is essentially an estuary hidden beneath the ice. They found a lot more than microbes, netting shrimp-like amphipods and spying eel-like fish on their screens.

Powell wants to go back and trap them.

"It's the ultimate form of ice-fishing," he says.

The big question is what supplies the energy for all this life.

The ocean beneath the ice here is dark and 800 kilometers from open water, so the sun is unlikely to be the energy source. Could the entire food chain - all the way up to amphipods and fish - rely on chemoautotrophic microbes?

If that's the case, it will be only the second chemosynthetic ecosystem known on the planet, says Tulaczyk, the first being deep-sea hydrothermal vents.

Despite being devoid of sunlight, vent ecosystems sustain large animals like tube worms - and it all rests on bacteria that get their energy from chemicals spewing out of the vents.

Geothermal and volcanic activity beneath the West Antarctic ice sheet could supply energy for large organisms too, not just microbes.

"We haven't found that in Antarctica yet, but it's a possibility that somewhere beneath the ice you are going to find something similar," says Tulaczyk.

"Deep beneath the ice,

they found fish and even

netted shrimp-like amphipods"
 

The researchers also want to explore a channel in the bedrock that may carry water from Lake Whillans to the estuary, as it could be bringing nutrients to the area.

Powell's team plans to lower a 7-metre-long remotely operated underwater vehicle, bristling with instruments, down a borehole to find out more.

"It's a cigar-shaped cylinder when it goes through the hole, and once it gets into the water it goes through a transformer sort of thing and opens up, and swims about in an open configuration," says Powell.

It's not just about finding new life forms here on Earth.

Exploring subglacial Antarctica may boost efforts to look for life elsewhere in the solar system, such as on the frozen moons Europa and Enceladus.

Both harbor liquid water under their vast icy surfaces.

"We don't expect to find a photosynthetically driven ecosystem [there]," says Tulaczyk.

 

"So having a continent that has a chemosynthetically driven system beneath the ice is a nice analogue to pretty much everywhere else that we hope to go and look for life that hasn't originated on Earth."

We have come a long way from the early days of Antarctic exploration.

Less than 150 years ago, geologists thought Antarctica's ice was anchored to the peaks of a volcanic archipelago. No one suspected it hid a continent, let alone life.

Our image of Earth's seventh continent has changed forever.

"It's come alive," says Tulaczyk.