Magnetic north, the point at the top of the Earth that determines compass headings, is shifting its position at a rate of about 40 miles per year. In geologic terms, it's racing from the Arctic Ocean near Canada toward Russia.
As a result, everyone who uses a compass, even as a backup to modern GPS navigation systems, needs to be aware of the shift, make adjustments or obtain updated charts to ensure they get where they intend to go, authorities say. That includes pilots, boaters and even hikers.
"You could end up a few miles off or a couple hundred miles off, depending how far you're going," said Matthew Brock, a technician with Lauderdale Speedometer and Compass, a Fort Lauderdalecompany that repairs compasses.
Although the magnetic shift has little impact on the average person and presents no danger to the Earth overall, it is costing the aviation and marine industries millions of dollars to upgrade navigational systems and charts.
Why is magnetic north shifting?
The Earth's core of hot liquid iron is constantly moving. That motion, combined with forces such as the Earth's rotation, dictate the position of magnetic north, not to be confused with geographic north, or the North Pole.
"Magnetic north is shifting all the time; it's a continuous process, not an event," said Jeffrey Love, a geophysicist with the U.S. Geological Survey Geomagnetism Program, based in Golden, Colo.
Over the past century, the shift has been increasing in speed. It went from creeping as slow as nine miles per year in the early 1900s to more than 35 miles per year in the 2000s. However, that acceleration also is part of natural cycle, Love said.
"In 10 to 20 years from now, it might be slowing down," he said.
Currently, the shift creates about a one-degree difference in compass direction every five years, Love said. Accordingly, the Federal Aviation Administration evaluates airport runway numbers every five years, said Kathleen Bergen, FAA spokeswoman.
The FAA could not say how many airports are affected. However, scores of large and small airports in the United States have either changed or plan to change their runways' numbers, which are based on compass directions.
Palm Beach International Airport changed its three runway numbers in December 2009 at a cost of $268,686. That included repainting the runway numbers, replacing signs and updating publications, said airport spokeswoman Casandra Davis.
Now the airport's main east-west runway is numbered 10-Left and 28-Right. Previously, it was 9-Left and 27-Right.
Fort Lauderdale-Hollywood International Airport plans to renumber its south runway as part of the $791 million expansion in 2014, said Mike Nonnemacher, the airport's director of operations. Shortly after that, the north runway numbers will be upgraded, he said.
"We wish to keep our runway designations close to what the compass says," Nonnemacher said.
When Miami International Airport's new north runway was built in 2003, it was given an updated number based on the magnetic shift, said airport spokesman Greg Chin.
"At that time, we had foresight to number the runway toward where it will be shifting," he said.
Because GPS navigation draws on satellites, it has no reliance on magnetic north. On the other hand, satellites and GPS systems can malfunction. For that reason, Tom Cartier recommends all pilots and boaters keep a compass handy as backup.
"The magnetic compass is what gets you home in your boat or plane when everything else quits," said Cartier, a senior deck instructor at Maritime Professional Training in Fort Lauderdale. "It's a very, very valuable piece of equipment."
Cartier said large ships and planes have sophisticated electronic navigation systems, but the vast majority of small boats and planes have magnetic compasses and rely on them heavily.
"They don't have the money to spend for a sophisticated system," he said.
He added that boaters should always bring updated maps, showing the latest corrections for the magnetic north shift, even if they have GPS.
The oil industry also relies on knowing the exact position of magnetic north, as companies use a device, similar to a compass, to determine what angle to drill into the earth, Love said.
"They don't drill straight down," he said. "They need to orient their drill bits to know which way they're going."
Many mobile companies equip smart phones with magnetometers, allowing their customers to see what direction they're heading. Those phones are likely to have a device that adjusts for the shift in magnetic north, said Manoj Nair, a research scientist with the National Oceanic and Atmospheric Administration's Geophysical Data Center.
Humans aren't the only ones affected by magnetic north. Birds that fly south for the winter and some sea turtles that migrate from Africa to South America must learn to adjust their senses so they end up migrating in the right direction, Love said.
"Some sea turtles live for a long period of time, up to 100 years," he said. "They have to accommodate the change in the magnetic field, because it changes substantially over 100 years."
kkaye@tribune.com or 954-572-2085