July 11, 2013

An iceberg slightly larger than the city of Chicago has finally calved (broken away) from Antarctica’s Pine Island Glacier (PIG), two years after scientists first spotted a 15-mile (24-kilometer) crack in the PIG’s ice shelf. (An ice shelf is the foreward part of an ice sheet that floats on water.) The PIG, located in West Antarctica, is shrinking faster than any other glacier on Earth. It also ranks number one among glaciers whose melting is contributing to the rise of global sea levels. The new iceberg, which has a surface area of 278 square miles (720 square kilometers), is now floating in the Amundsen Sea.

Scientists with NASA’s Operation IceBridge first noticed a crack in the PIG’s ice shelf in October 2011 while flying over and surveying the massive glacier. The crack, then about 15 miles (24 kilometers) long and 164 feet (50 meters) wide, had grown to 17 miles (28 kilometers) long and 1,770 feet (540 meters) at its widest point just before the iceberg split off, according to scientists at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. Scientists at the institute have been tracking the birth of the iceberg using the German Space Agency’s TerraSAR-X satellite.

The new iceberg that calved from the Pine Island Glacier appears in a satellite image from the German Space Agency on 8 July 2013. (DLR)

Calving is a natural process for Antarctic ice sheets and is not necessarily related to global warming. The PIG produced huge icebergs in 2001 and 2007. However, scientists have found that the PIG has grown significantly thinner and has begun to move faster toward the sea in recent decades. The glacier is currently responsible for about 10 percent of all the ice flowing into the sea from West Antarctica.

The new iceberg, however, did not set any records for size. In March 2000, one of the largest icebergs ever recorded separated from the Ross Ice Shelf. Named B-15, it was around 4,250 square miles (11,000 square kilometers) in surface area—about the size of the island of Jamaica—and possibly more than 1,000 feet (300 meters) thick. Even after drifting into the warmer waters of the Southern Ocean and breaking apart, some pieces survived more than 10 years. In January 2005, a huge chunk of B-15 ran aground in Antarctica’s McMurdo Sound in the Ross Sea, devastating Adélie penguin colonies. The iceberg prevented adult Adélie penguins from feeding in normally open waters. Many penguin chicks died of starvation while their parents trudged across the vast ice sheet in search of food.

Additional World Book articles:

• Amundsen, Roald
• Ice formation
• Ross Dependency
• The Great Meltdown (a special report)
• Science in Antarctica (a special report)

April 14, 2012

On this day in 1912 the mighty ocean liner Titanic hit an iceberg in the North Atlantic and later sank, resulting in the loss of 1,500 lives. The ship, the largest and most costly ever built at that time, had been declared unsinkable. Yet it did sink, and on its maiden voyage from Southampton, England, to New York City. Blame for the disaster has been placed on everybody and everything, from the ship’s captain to substandard coal and even flawed rivets. Now, 100 years after the liner broke apart and went down, scientists are proposing that two rare states of nature may have played major roles in the catastrophe. (The Titanic hit the iceberg at about 11:40 p.m. on the 14th and sank approximatley 2.5 hours later on the 15th.)

The Titanic sank on April 15, 1912. (Courtesy of AP/Wide World)

Researchers from Texas State University–San Marcos and Sky & Telescope magazine have discovered that Earth came unusually close to the sun and moon between December 1911 and February 1912. This configuration intensified their gravitational pull, resulting in record high tides. The researchers suggested that the high tides unleashed masses of icebergs from along the coastlines of Labrador and Newfoundland and set them adrift into the North Atlantic. “We don’t claim that our idea is conclusive,” notes Donald Olson, a physicist at Texas State. . . . [But] “we found there had been remarkable tidal events around the globe–in England and New Zealand.” Contemporary newspaper accounts back his claim. Soon after the disaster, The New York Times quoted U.S. officials as saying that the winter had produced “an enormously large crop of icebergs.”

Scientists believe that the Titanic hit an iceberg that broke off from Newfoundland and Labrador and drifted into its path. (World Book Map)

In Titanic: A Very Deceiving Night, Titanic historian Tim Maltin proposes that these very icy waters may have produced an unusual type of mirage that masked the size and location of  icebergs. Mirages occur at sea when cold air bends light rays downward. This causes images to become distorted, rather like the wavy reflections in a funhouse mirror. Matlin suggests that such warped images may have confused the men on watch aboard the Titanic about the size and distance of the iceberg.

Perhaps because of the luxury of the ship and the number of millionaires who went down with it–including real estate tycoon John Jacob Astor and Macy’s Department Store owner Isidor Straus–the Titanic has never lost its allure.  A Broadway musical, The Unsinkable Molly Brown, was written about the colorful life of one Titanic survivor. A number of films have also been made about the disaster. The most recent, Titanic (1997), was the second-most commercially successful film of all time. The writer and director, James Cameron, won an Academy Award as best director for Titanic, which also won 10 other awards, including best picture.

Additional World Book articles:

• Optics
• Archaeology 1997 (Back in Time article)
• Motion pictures 1997 (Back in Time article)
• Theater 1960 (Back in Time article)