The International Convention for the Safety of Life at Sea (SOLAS), a major treaty governing merchant ships, mandates that all vessels crossing the North Atlantic during the months when there is a threat from icebergs (usually February to July) receive and read the Ice Patrol's notifications. However, they are not compelled to act on them, hence the 19 sinkings that have occurred since 1913.
An iceberg, which is technically a piece of ice longer than 45 feet at the waterline, has to make it past 48 degrees north – a line of latitude that passes through northern France in Europe – before the Patrol counts it as having the potential to interfere with shipping. The Titanic sank just south of 42 degrees north, and icebergs have been spotted in waters as far south as those parallel to Washington D.C.
AIRCRAFT SPOT WHAT SHIPS CANNOT
Surprisingly, it wasn't until 1946 that the Coast Guard started using aircraft to supplement its ships in the search for these monstrous and potentially lethal pieces of ice.
International Ice PatrolPatrols now made by plane were once made by ship.
"Up until that time it was just cutters," Hicks said. "Generally they would assign two or three cutters and they would take turns going out from Halifax or St. Johns, finding the southern most iceberg and staying with the iceberg and radioing their position to ships coming across the Atlantic."
In 1973, the Patrol stopped using ships and has relied on airplanes ever since.
"The C130 aircraft can cover a much larger area in a lot less time," Hicks said. "They also have the capacity to carry side-looking airborne radar, which is an old but very effective radar system. It was designed to detect oil spills but it works pretty well for icebergs."
The planes, which conduct 12 or more missions each month, normally fly for six to eight hours at an altitude of between 5,500 and 8,000 feet. Yet because of the weather, even at that height, the sea is visible only 30 percent of the time.
"We will descend as low as 400 feet if we detect a target on the radar that we can't identify and the cloud base is low," Hicks said. "Hopefully we will see the surface by that point."
International Ice PatrolA bomb crater after the U.S. Navy's failed experiment to blow up icebergs using airborn bombs and floating mines.
Once an iceberg has been detected, its size and location are plotted onto a map, which is marked with all known ice. The map is then disseminated to ships crossing the Atlantic – there are more than a dozen each day – and is posted on the Patrol's website. To ensure a margin of safety, the line depicting the limits the ice is usually drawn 30 miles south of the actual last known position of an iceberg.
When the planes aren't flying, the maps are still updated every 24 hours.
"We forecast where we think the bergs are going using a computer model," Hicks said. "That model uses ocean currents, winds, water temperature and waves to predict where the iceberg is going to drift and how long it is going to take to melt."
Hicks acknowledges that the model is not flawless.
"In the short term it does a pretty good job," he said. "But as you go beyond six or seven days, it becomes less reliable, just like a weather forecast, so that's why we patrol so often."
Studies show that icebergs generally drift no more than 12 miles in a day.
450 ICEBURGS A YEAR
Only once, in 1966, had the Patrol recorded zero icebergs in a season - until last year. In 2006, the number of icebergs sighted past 48 degrees north, and therefore inside shipping lanes, was again zero, according to the Patrol's annual report. This is a stunning change, given that in 2003 there were 927 icebergs on record.
"On average we expect to see about 450 icebergs a year," said Don Murphy, the oceanographer, who explains that all of the icebergs that appear in the North Atlantic are produced by ice flowing slowly but steadily from glaciers in Greenland into the sea and breaking away. The floating chunks of frozen water are then at the mercy of ocean currents, which initially carry them north and then west across to Canada's Baffin Bay before the Labrador Current pushes them south.
"The currents are weak and variable along Baffin island so every iceberg's southward track is characterized by long periods of no motion," Murphy said. "Most will go aground on a pinnacle or submerged mountain around the edge of the continental shelf and you have to wait for them to deteriorate until finally they can float off the bottom and can continue their path. Then Boom! They get stuck again or get driven so far into a bay that they never make it out and waves destroy them."
