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Photo courtesy: Public domain/Public Domain
Summer ice is melting at a faster rate in the Antarctic peninsula than at any time in the last 1,000 years, new research has shown.
The evidence comes from a 364-metre ice core containing a record of freezing and melting over the previous millennium.
Layers of ice in the core, drilled from James Ross Island near the northern tip of the peninsula, indicate periods when summer snow on the ice cap thawed and then refroze.
By measuring the thickness of these layers, scientists were able to match the history of melting with changes in temperature.
Lead researcher Dr Nerilie Abram, from the Australian National University and British Antarctic Survey (BAS), said: "We found that the coolest conditions on the Antarctic peninsula and the lowest amount of summer melt occurred around 600 years ago.
"At that time temperatures were around 1.6C lower than those recorded in the late 20th century and the amount of annual snowfall that melted and refroze was about 0.5%.
"Today, we see almost 10 times as much (5%) of the annual snowfall melting each year.
"Summer melting at the ice core site today is now at a level that is higher than at any other time over the last 1,000 years. And while temperatures at this site increased gradually in phases over many hundreds of years, most of the intensification of melting has happened since the mid-20th century."
Levels of ice melt on the Antarctic peninsula were especially sensitive to rising temperature during the last century, he said.
"What that means is that the Antarctic peninsula has warmed to a level where even small increases in temperature can now lead to a big increase in summer melt," Abram added.
Dr Robert Mulvaney, from the British Antarctic Survey, who led the ice core drilling expedition in 2008 and co-authored a paper on the findings published on Sunday in the journal Nature Geoscience.
He said: "Having a record of previous melt intensity for the Peninsula is particularly important because of the glacier retreat and ice shelf loss we are now seeing in the area.
"Summer ice melt is a key process that is thought to have weakened ice shelves along the Antarctic peninsula leading to a succession of dramatic collapses, as well as speeding up glacier ice loss across the region over the last 50 years."
The ice core record suggested a link between accelerated melting and man-made global warming. But a different and more complex picture has emerged from another region of Antarctica.
A separate US study, published in the same journal, shows that thinning ice from the West Antarctic Ice Sheet Divide cannot confidently be blamed on greenhouse gas emissions.
An ice core record from this site indicates a strong influence from unusual conditions in the tropical Pacific during the 1990s.
In that decade, an El Niño event – a cyclical system of winds and ocean currents that can affect the world's weather – caused rapid thinning of glaciers in the west Antarctic.
Summer ice is melting at a faster rate in the Antarctic peninsula than at any time in the last 1,000 years, a new study has shown. Photo courtesy: Nasa/AFP/Getty Images
The spike in temperature was little different from others that occurred in the 1830s and 1940s, which also saw prominent El Niño events.
"If we could look back at this region of Antarctica in the 1940s and 1830s we would find that the regional climate would look a lot like it does today, and I think we also would find the glaciers retreating much as they are today," said lead author Prof Eric Steig, from the University of Washington.
He said the same was not true for the Antarctic peninsula, the part of the continent closer to South America. Here, more dramatic changes were "almost certainly" a result of human-induced global warming.
Here's a video of a city-sized glacier collapsing.
The Union Jack flies over a field camp at Lake Ellsworth. In the background are the Ellsworth Mountains, the highest range in Antarctica. Photo courtesy: Neil Ross/University of Edinburgh
Could Nessie have a cold-blooded cousin that may have survived the millenia locked in a previously undiscovered, untouched underground lake in Antarctica? Is there any life at all in a frozen, underground lake? Time and science will tell.
After 16 years of meticulous planning, a team of British scientists is finally ready to journey to a remote, windswept plain in Antarctica, where they will drill deep into the ice to take the first-ever samples from a lake cut off from the sunlit world for up to 1 million years.
Their target, Lake Ellsworth, may house tiny organisms utterly new to science, and may proffer the first solid clues regarding the age of the massive ice sheet that covers it.
The lake is 7 mi long, 1 mi wide and about 500' deep (12 km by 3 km by 150 m). It lies in the middle of West Antarctica, hidden beneath nearly 2 mi (3 km) of ice, and scientists plan to use a specially built hot water drill to reach its fresh waters.
A team of a dozen researchers and engineers will assemble at a remote field camp in late November, and drilling is slated to begin in December, said Martin Siegert, the lead investigator for the project and a glaciologist at the University of Bristol.
The massive undertaking is aimed at one simple goal: to fetch 24 small titanium canisters of lake water — just 3.3 ounces (100 milliliters) each — along with sediment from the lake bottom, all scooped up with sterile equipment that will keep both samples and the lake environment utterly pristine.
It will take three straight days of drilling to reach the surface of Lake Ellsworth. Once the lake is breached, Siegert said, the scientists will have about 24 hours to retrieve all the samples before the borehole freezes over again.
However, if the work isn't completed in 24 hours, the team has enough fuel to melt through the ice a second time, which would buy them more time. "Some snags will happen, so you have to build in redundancy," Siegert told OurAmazingPlanet.
The scientists will be able to watch the action live as it unfolds beneath them. The team has affixed tiny, high-definition video cameras to the probe and the sediment corer, along with bright lights to illuminate the darkness. One camera looks up toward the surface, and one looks down.
"We're really looking forward to getting images back," Siegert said.
Although the canisters of lake water won't be opened until they are returned to clean rooms back in England for analysis, the world won't have to wait to learn what life forms — if any — lurk in Lake Ellsworth.
As the water is sucked into the titanium canisters, it will be pushed through a filter — a mesh so fine that, if any microbes are indeed living in the frigid, pitch-dark lake, some will end up caught on the filter.
"So when the probe comes to the surface, we won't be able to analyze the water, but we will be able to analyze the filter immediately," Siegert said. "We will look at it under a microscope within a few hours. So the question, 'Is there life in the lake?,' we will have an answer very quickly."
Yet that is not the only question scientists are seeking to answer. Scientists are hoping that the layers of sediment plucked from the bottom of Lake Ellsworth will offer clues to the true age of the West Antarctic Ice Sheet.
"We don't know. It could be 100,000 to 1 million years old," Siegert said. "We think it's at risk of change, but what we need is to understand how likely that is, and gain an appreciation of when the ice sheet last decayed because of environmental conditions," he said.
If all goes according to plan, scientists could have samples of the ancient lake in hand by Dec. 18, 2012.
It's likely the British will be the first of three groups currently seeking to sample a long-buried Antarctic lake.
Earlier this year, after more than a decade of drilling, a Russian team in East Antarctica finally breached Lake Vostok, the largest hidden lake on the continent.
The approach of the brutal winter season, along with the nature of the drill equipment, prevented the Russian team from bringing back samples; however, many scientists question the integrity of any water retrieved from Lake Vostok. The Russian team has used kerosene and other materials to keep the borehole open, and there are fears of sample contamination.
In early 2013, an American team is planning to drill to hidden lakes in West Antarctica.
Siegert said his team is finally feeling relaxed after years of furious work, and said he can't speculate what they'll find in Lake Ellsworth.
"Honestly, we just don't know until we do it," he said. "That's one of the wonderful things about this project. We're very excited about doing our work."
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