NASA satellite tracks ship-menacing iceberg
An enhanced resolution image showing the iceberg B10A (upper left) next to the continent of Antarctica. The image was produced using data from the QuikScat satellite (click image to enlarge).|
Movie showing the movement of the iceberg:|
359k mpeg movie
September 7, 1999
Web posted at: 5:18 p.m. EDT (2118 GMT)
By Robin Lloyd
CNN Interactive Senior Writer
(CNN) -- Monitoring a block of ice sounds about as exciting as watching grass grow, but what if it's an iceberg the size of Rhode Island?
Many international shippers, climatologists and federal employees anxiously await daily updates from a NASA satellite that recently sighted and now tracks a previously lost iceberg called B10 A off the coast of Antarctica.
The SeaWinds radar instrument, flying aboard the QuikScat satellite, stumbled upon the mammoth ice block in July in the Drake Passage shipping lane and now tracks it for a branch of the government, called the National Ice Center.
"The real danger is not the large iceberg," said David Long, a member of the SeaWinds science team from Brigham Young University in Utah. "But it's constantly dropping off smaller pieces. Those are harder to track. Those are the ones that are the largest threat. It's got dandruff."
A bonus find
Iceberg B10A, which measures about 38 by 77 kilometers (about 24 miles by 48 miles), was spotted during SeaWinds' first pass over Antarctica.
The QuikScat satellite
When the berg was rediscovered, it was heading northeast between Tierra del Fuego at the southern tip of South America and the Antarctic Peninsula.
SeaWinds, launched in June and used primarily to monitor winds at ocean surfaces, orbits Earth aboard the QuikScat satellite and bounces microwaves off the seas to study climate-driving winds there. Finding the iceberg was a bonus, Long said.
The berg snapped off Antarctica seven years ago and since has drifted in and out of the shipping lane. It extends about 90 meters (300 feet) above water and may reach as deep as 300 meters (1,000 feet) below the ocean's surface.
That means it could be under a ship long before it was spotted in the dark, foggy area currently shrouded around the clock in winter darkness.
A collision with B10A itself is less likely than a ship hitting one of its "calves," or pieces that later break off. Although it's winter now in the area, summer is fast approaching and the berg is not expected to remain intact for three months.
Cruise ships and research vessels that use the shipping lane in the coming months will want detailed reports of B10A's movements, which SeaWinds indirectly will supply. The mission is managed by NASA's Jet Propulsion Laboratory.
Ice Center heralds discovery
Long generally uses SeaWinds data to study the melting of Greenland, tropical deforestation and the movement of Antarctic ice sheets. But during a visit to JPL this summer, he noticed something odd while looking over the mission's first data.
The huge iceberg stood out as a bright spot, Long said. The resolution on the SeaWinds instrument is very low -- it sees nothing smaller than 4 km across -- but that was good enough to net the humongous iceberg.
When Long reported the finding to the National Ice Center, he got an enthusiastic response.
"They all yelled out, 'It must be B10A,'" Long said. "Sure enough, they'd lost track of it. They'd been tracking it for several years."
The National Ice Center in Suitland, Maryland, provides sea-ice forecasts for U.S. military and allies, the civil sector and the Departments of Commerce and Transportation. When B10A was rediscovered this summer, the National Ice Center issued an iceberg navigation warning to the Argentine government.
Federal agencies were so concerned about the missing iceberg that they had sent a ship out to find it and had failed so far. No damage to ships has been reported.
"This is exciting that we can use this for something very different from what it was designed for," Long said.
Iceberg moves like a paramecium
B10A, which took hundreds of thousands of years to form, broke off the end of the Thwaites glacier of Antarctica in 1992 and has been drifting in the ocean ever since, driven by ocean currents and wind.
In 1995, the iceberg broke in half, but was being tracked on a regular basis.
Although the National Ice Center relied on conventional ice-tracking methods -- ships' radar, shipping reports, optical images from satellites and microwave sensor data -- they lost track of B10A earlier this year in the poor visibility of the dark Antarctic winter.
Now that it has been found, scientists see that B10A is moving northward at 8 km/h in the main shipping lane. But its movements are erratic.
"Ever see a paramecium swimming in the water?" Long said. "That's exactly what it looks like."
Daily updates on the iceberg are important because not only can B10A crack up, its calves may have a tendency to suddenly roll over.
"It's really a danger. At any moment it could flip over and take the boat with it," Long said. "They get unstable."
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