Giant iceberg, 965sqmi (2500sqkm, 400m thick) split fr Antarctica, holding "enough water to fill River Thames 100 times."

An giant iceberg has broken off from Antarctica, created when it was hit by another iceberg two weeks ago. The size of Luxemberg, it could disrupt ocean circulation patterns.

The 965 sq mile (2,500 sq km) block of ice broke off from the Mertz Glacier which ends in a floating tongue of ice that protrudes 100 miles (160 km) out into the Southern Ocean. The 'calving' - or splitting of the ice sheet - resulted a collision with another iceberg.

Glaciers are melting, sea levels are rising, cloud forests are drying, and wildlife is scrambling to keep pace. It's becoming clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than in the last 650,000 years.

A large iceberg was spotted off an island about halfway between Antarctica and Australia, a rare sight in waters so far north.

A giant iceberg measuring some 700 metres (2,300 feet) long with an estimated depth of 350 metres has been spotted floating off Australia and could be headed for New Zealand.

(quote)

The ice shelves in the southern part of the Antarctic Peninsula appear to be disappearing because of climate change, according to a new report from the U.S. Geological Survey and the British Antarctic Survey. "The loss of ice shelves is evidence of the effects of global warming," says USGS scientist and lead author Jane Ferrigno. Melting of the West Antarctic part alone of the Antarctic ice sheet would cause a worldwide sea-level rise of approximately 18 feet. According to the report, "the resulting rise in sea level could severely impact the densely populated coastal regions on Earth." A 965 sq mile (2,500 sq km) block of ice broke off from the Mertz Glacier which ends in a floating tongue of ice that protrudes 100 miles (160 km) out into the Southern Ocean, which could disrupt ocean currents. Flooding could become a major problem if the giant ice berg, the size of Luxembourg, which holds enough water to fill the River Thames 100 times, begins to melt. Newly released images from NASA and the National Snow and Ice Data Center show that the Arctic's melt season has lengthened significantly over the past few decades. The melting season - i.e. the length of time in which continuous melting occurs - has increased on average by 6.4 days for every decade between 1979 and 2007.

An iceberg the size of Luxembourg has sheared off from the Antarctic - threatening global weather chaos. Scientists fear it could mean bitterly cold winters in Britain, and the north Atlantic generally, within a decade. Australian glaciologist Dr Neal Young warned production of cold salty water, which keeps the earth's climate temperate, could be badly hit by the melting ice.

And flooding could become a major problem if the 965-square mile glacier, which holds enough water to fill the River Thames 100 times, moves north and begins to melt. Dr Young said: "The effects may not be immediate but the ice split will have implications."

Sea life is also under threat, including a major colony of European penguins, as oxygen levels in oceans could plummet. Dr Young added: "Penguins and other wildlife that use the area for feeding could be hit."

The giant slab of ice, which is 400 metres thick, was created when it was hit by broke off another iceberg two weeks ago. The two icebergs are now drifting close together about 100 miles north of Antartica.

NASA: Arctic melt season lengthening
Newly released images from NASA and the National Snow and Ice Data Center show that the Arctic's melt season has lengthened significantly over the past few decades.

The melting season—i.e. the length of time in which continuous melting occurs—has increased on average by 6.4 days for every decade between 1979 and 2007. Around the lower-latitude edges of the ice pack, however, this lengthening was far above the average.

According to NASA, researchers collect this data by using satellite observations of the microwave energy radiated from the Arctic ice, which reveals the appearance of even small amounts of melt water.

In January, Arctic sea ice grew by about 13,000 square miles (34,000 sq km) a day, which is a bit more than one-third the pace of ice growth during the 1980s, and less than the average for the first decade of the 21st century. Arctic ice cover is important to the rest of the world because the Arctic is the globe's biggest weather-maker, sometimes dubbed Earth's air-conditioner for its ability to cool down the planet. If Arctic ice fails to build up sufficiently during the dark, cold winter months, it is likely to melt faster and earlier when spring comes.

Glaciers are melting, sea levels are rising, cloud forests are drying, and wildlife is scrambling to keep pace. It's becoming clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than in the last 650,000 years.

We call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. As the Earth spins each day, the new heat swirls with it, picking up moisture over the oceans, rising here, settling there. It's changing the rhythms of climate that all living things have come to rely upon.

What will we do to slow this warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the face of the Earth as we know it—coasts, forests, farms and snow-capped mountains—hangs in the balance.

Greenhouse effect

The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse.

First, sunlight shines onto the Earth's surface, where it is absorbed and then radiates back into the atmosphere as heat. In the atmosphere, “greenhouse” gases trap some of this heat, and the rest escapes into space. The more greenhouse gases are in the atmosphere, the more heat gets trapped.

Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be much colder if it had no atmosphere. This greenhouse effect is what keeps the Earth's climate livable. Without it, the Earth's surface would be an average of about 60 degrees Fahrenheit cooler. In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse effect by making carbon dioxide, a greenhouse gas. He kicked off 100 years of climate research that has given us a sophisticated understanding of global warming.

Levels of greenhouse gases (GHGs) have gone up and down over the Earth's history, but they have been fairly constant for the past few thousand years. Global average temperatures have stayed fairly constant over that time as well, until recently. Through the burning of fossil fuels and other GHG emissions, humans are enhancing the greenhouse effect and warming Earth.

Scientists often use the term "climate change" instead of global warming. This is because as the Earth's average temperature climbs, winds and ocean currents move heat around the globe in ways that can cool some areas, warm others, and change the amount of rain and snow falling. As a result, the climate changes differently in different areas.

Aren't temperature changes natural?

The average global temperature and concentrations of carbon dioxide (one of the major greenhouse gases) have fluctuated on a cycle of hundreds of thousands of years as the Earth's position relative to the sun has varied. As a result, ice ages have come and gone.

However, for thousands of years now, emissions of GHGs to the atmosphere have been balanced out by GHGs that are naturally absorbed. As a result, GHG concentrations and temperature have been fairly stable. This stability has allowed human civilization to develop within a consistent climate.

Occasionally, other factors briefly influence global temperatures. Volcanic eruptions, for example, emit particles that temporarily cool the Earth's surface. But these have no lasting effect beyond a few years. Other cycles, such as El Niño, also work on fairly short and predictable cycles.

Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the industrial revolution. Changes this large have historically taken thousands of years, but are now happening over the course of decades.

Why is this a concern?

The rapid rise in greenhouse gases is a problem because it is changing the climate faster than some living things may be able to adapt. Also, a new and more unpredictable climate poses unique challenges to all life.

Historically, Earth's climate has regularly shifted back and forth between temperatures like those we see today and temperatures cold enough that large sheets of ice covered much of North America and Europe. The difference between average global temperatures today and during those ice ages is only about 5 degrees Celsius (9 degrees Fahrenheit), and these swings happen slowly, over hundreds of thousands of years.

Now, with concentrations of greenhouse gases rising, Earth's remaining ice sheets (such as Greenland and Antarctica) are starting to melt too. The extra water could potentially raise sea levels significantly.

As the mercury rises, the climate can change in unexpected ways. In addition to sea levels rising, weather can become more extreme. This means more intense major storms, more rain followed by longer and drier droughts (a challenge for growing crops), changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from glaciers.

Scientists are already seeing some of these changes occurring more quickly than they had expected. According to the Intergovernmental Panel on Climate Change, eleven of the twelve hottest years since thermometer readings became available occurred between 1995 and 2006.

Giant iceberg could disrupt ocean currents. An iceberg the size of Luxembourg that has broken off from a glacier in Antarctica could disrupt ocean circulation patterns, scientists have said.

The 965 sq mile (2,500 sq km) block of ice broke off from the Mertz Glacier which ends in a floating tongue of ice that protrudes 100 miles (160 km) out into the Southern Ocean.

The 'calving' - or splitting of the ice sheet - resulted a collision with another iceberg. This 97 km long slab of ice is a remnant of an iceberg of more than 5,000 sq km that broke off, or calved, in 1987, making it one of the largest icebergs ever recorded in Antarctica.

The Mertz glacier iceberg is among the largest recorded for several years. In 2002, a iceberg about 200 km long broke off from Antarctica's Ross Ice Shelf. In 2007, an iceberg roughly the size of Singapore broke off from the Pine Island Glacier in West Antarctica.

Massom said the shearing off of the ice tongue and the presence of the Mertz and B-9B icebergs could affect global ocean circulation. The area is an important zone for the creation of dense, salty water that is a key driver of global ocean circulation. This is produced in part through the rapid production of sea ice that is continually blown to the west.

"Removal of this tongue of floating ice would reduce the size of that area of open water, which would slow down the rate of salinity input into the ocean and it could slow down this rate of Antarctic bottom water formation," he said.

He said there was a risk both icebergs would become grounded on banks or shoals in the area, disrupting the creation of the dense, salty water and the amount that sinks to the bottom of the ocean, he said.

Oceans currents help to shifting heat around the globe and are a vital part of marine ecosystems.

The ice shelves in the southern part of the Antarctic Peninsula appear to be disappearing because of climate change, according to a new report from the U.S. Geological Survey and the British Antarctic Survey. "The loss of ice shelves is evidence of the effects of global warming," says USGS scientist and lead author Jane Ferrigno. Melting of the West Antarctic part alone of the Antarctic ice sheet would cause a worldwide sea-level rise of approximately 18 feet. According to the report, "the resulting rise in sea level could severely impact the densely populated coastal regions on Earth."

In the worst-case scenario, the potential sea-level rise if the entire Antarctic ice sheet melts is estimated to be 213 to 240 feet.

"The changes exhibited in the region are widely regarded as among the most profound and unambiguous examples of the effects of global warming yet seen on the planet," the authors write in the report.

Since 1998, the ice lost from just one of the five ice shelves in the study totals more than 1,500 square miles, an area larger than the state of Rhode Island.

Scientists used satellite and aerial photographs and maps dating back to the 1940s as sources for the report. The ice shelves are attached to the continent and already floating, holding in place the Antarctic ice sheet that covers about 98 percent of Antarctica.

The report acknowledges that while parts of the Antarctic ice sheet are thickening, on balance, it is probably becoming thinner overall.

The full report, "Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009" is available online by
Jane G. Ferrigno *1
Alison J. Cook *2
Amy M. Mathie *3
Richard S. Williams, Jr. *4
Charles Swithinbank *5
Kevin M. Foley *1
Adrian J. Fox *2
Janet W. Thomson *6, and
Jörn Sievers *7

*1 U.S. Geological Survey, Reston, VA U.S.A.
*2 British Antarctic Survey, Cambridge, United Kingdom
*3 U.S. Geological Survey, Vancouver, WA U.S.A.
*4 U.S. Geological Survey, Woods Hole, MA U.S.A.
*5 Scott Polar Research Institute, University of Cambridge, United Kingdom
*6 Formerly with British Antarctic Survey, Cambridge, United Kingdom
*7 Bundesamt für Kartographie und Geodäsie (formerly Institut für Angewandte Geodäsie), Frankfurt am Main, Germany

(unquote)

Photos courtesy of Mirror.co.uk, AFP, Paul Nicklen / National Geographic, Momento 24, and Florida State University