The Tampa Tribune
The airport has closed its primary runway until Jan. 13 to repaint the numeric designators at each end and change taxiway signage to account for the shift in location of the Earth's magnetic north pole.
The closure of the west parallel runway will result in more activity on the east parallel runway and more noise for residential areas of South Tampa.
The busiest runway will be re-designated 19R/1L on aviation charts. It's been 18R/36L, indicating its alignment along the 180-degree approach from the north and the 360-degree approach from the south.
Later this month, the airport's east parallel runway and the seldom used east-west runway will be closed to change signage to their new designations.
The Federal Aviation Administration required the runway designation change to account for what a National Geographic News report described as a gradual shift of the Earth's magnetic pole at nearly 40 miles a year toward Russia because of magnetic changes in the core of the planet.or had sought to delay the decision until June 30, 2008. It had already missed a January 2008 deadline.
SOURCE: The Tampa Tribune
for National Geographic News
December 15, 2005
Santa better check his compass, because the North Pole is shifting—the north magnetic pole, that is, not the geographical one. New research shows the pole moving at rapid clip - 25 miles (40 kilometers) a year.
Over the past century the pole has moved 685 miles (1,100 kilometers) from Arctic Canada toward Siberia, says Joe Stoner, a paleomagnetist at Oregon State University. At its current rate the pole could move to Siberia within the next half-century, Stoner said.
"It's moving really fast," he said. "We're seeing something that hasn't happened for at least 500 years."
Stoner presented his team's research at the American Geophysical Union's meeting last week in San Francisco. Lorne McKee, a geomagnetic scientist at Natural Resources Canada, says that Stoner's data fits his own readings.
"The movement of the pole definitely appears to be accelerating," he said.
Not a Reversal
The shift is likely a normal oscillation of the Earth's magnetic field, Stoner said, and not the beginning of a flip-flop of the north and south magnetic poles, a phenomenon that last occurred 780,000 years ago.
Such reversals have taken place 400 times in the last 330 million years, according to magnetic clues sealed in rocks around the world. Each reversal takes a thousand years or more to complete.
"People like to think something special is happening in their lifetimes, but despite the dramatic changes, I don't see any evidence of it," Stoner said. "It's probably just a normal wandering of the pole."
The north magnetic pole shifts constantly, in loops up to 80 kilometers (50 miles) wide each day.
The recorded location of the pole is really an average of its daily treks, which are driven by fluctuations in solar radiation.
The pole is currently at about 80º north latitude and 104º west longitude, in the Canadian territory of Nunavut.
Importance of the Pole
Pinpointing the precise location of the north magnetic pole is important for navigation: As you move closer to the pole, the direction north indicated by your compass becomes less accurate.
The pole also plays a role in the Northern Lights, which form when solar radiation bounces across the magnetic field in the upper atmosphere. As the north magnetic pole drifts, it will take the Northern Lights with it.
But for scientists, studying the field provides a tantalizing glimpse into the fiery center of the Earth.
The planet's outer core of molten iron spins constantly, acting as a giant dynamo, or electromagnet.
This energy interacts with the rocky mantle of the Earth, which is also shifting, resulting in a complex, ever-changing magnetic field.
"We're close to having a much better understanding on how the field fluxes," Stoner said.
The first readings of the north magnetic pole date to 1831, when Sir John Ross and his ship searching for the Northwest Passage became ice-bound.
To pass the time he sent out a team with a compass to take readings, and the team soon found a dipole—an area with compass readings pointing both north and south—in what is now Nunavut. It was the north magnetic pole.
While historical readings date back almost two centuries, Stoner's team wanted to take a deeper look into the past.
They went to the Arctic and pulled 4.5-meter-long (15-foot-long) cores of mud and clay from the bottom of frigid lakes.
Each year, snowmelt deposits a layer of silt at the bottom of the lakes, which is then covered with a layer of clay. "There are these distinct couplets every year," Stoner said. "It's a lot like counting rings in a tree."
Back at his laboratory at Oregon State University, Stoner and his team sliced the cores into thin sections.
They then ran each section through an instrument that reads tiny magnetic particles in the silt to reveal both the direction and intensity of the magnetic field.
Each section comprises five to ten layers, or five to ten year's worth of magnetic readings.
"We can't get down to the yearly scale yet," Stoner said, "but that's getting to be a pretty tight resolution."
In contrast, similar techniques used to measure magnetism in rock have yielded much coarser resolutions of thousands to tens of thousands of years.
Besides recording the movement of the pole, the silt cores also show a recent drop in the strength of the magnetic field, Stoner said, a phenomenon that often accompanies north-south reversals.
But research by French scientists published in 2003 suggests that such "jerks" in the magnetic field—abrupt shifts in intensity and direction—occur often, not just during reversals.
SOURCE: National Geographic
Every few years, scientist Larry Newitt of the Geological Survey of Canada goes hunting. He grabs his gloves, parka, a fancy compass, hops on a plane and flies out over the Canadian arctic. Not much stirs among the scattered islands and sea ice, but Newitt's prey is there--always moving, shifting, elusive.
Credit: Geological Survey of Canada. [More]
His quarry is Earth's north magnetic pole.
At the moment it's located in northern Canada, about 600 km from the nearest town: Resolute Bay, population 300, where a popular T-shirt reads "Resolute Bay isn't the end of the world, but you can see it from here." Newitt stops there for snacks and supplies--and refuge when the weather gets bad. "Which is often," he says.
Scientists have long known that the magnetic pole moves. James Ross located the pole for the first time in 1831 after an exhausting arctic journey during which his ship got stuck in the ice for four years. No one returned until the next century. In 1904, Roald Amundsen found the pole again and discovered that it had moved--at least 50 km since the days of Ross.
The pole kept going during the 20th century, north at an average speed of 10 km per year, lately accelerating "to 40 km per year," says Newitt. At this rate it will exit North America and reach Siberia in a few decades.
Keeping track of the north magnetic pole is Newitt's job. "We usually go out and check its location once every few years," he says. "We'll have to make more trips now that it is moving so quickly."
Earth's magnetic field is changing in other ways, too: Compass needles in Africa, for instance, are drifting about 1 degree per decade. And globally the magnetic field has weakened 10% since the 19th century. When this was mentioned by researchers at a recent meeting of the American Geophysical Union, many newspapers carried the story. A typical headline: "Is Earth's magnetic field collapsing?"
Probably not. As remarkable as these changes sound, "they're mild compared to what Earth's magnetic field has done in the past," says University of California professor Gary Glatzmaier.
Magnetic stripes around mid-ocean ridges reveal the history of Earth's magnetic field for millions of years. The study of Earth's past magnetism is called paleomagnetism. Image credit: USGS. [More]Sometimes the field completely flips. The north and the south poles swap places. Such reversals, recorded in the magnetism of ancient rocks, are unpredictable. They come at irregular intervals averaging about 300,000 years; the last one was 780,000 years ago. Are we overdue for another? No one knows.
According to Glatzmaier, the ongoing 10% decline doesn't mean that a reversal is imminent. "The field is increasing or decreasing all the time," he says. "We know this from studies of the paleomagnetic record." Earth's present-day magnetic field is, in fact, much stronger than normal. The dipole moment, a measure of the intensity of the magnetic field, is now 8 x 1022 amps x m2. That's twice the million-year average of 4 x 1022 amps x m2.
To understand what's happening, says Glatzmaier, we have to take a trip ... to the center of the Earth where the magnetic field is produced.
At the heart of our planet lies a solid iron ball, about as hot as the surface of the sun. Researchers call it "the inner core." It's really a world within a world. The inner core is 70% as wide as the moon. It spins at its own rate, as much as 0.2o of longitude per year faster than the Earth above it, and it has its own ocean: a very deep layer of liquid iron known as "the outer core."
Earth's magnetic field comes from this ocean of iron, which is an electrically conducting fluid in constant motion. Sitting atop the hot inner core, the liquid outer core seethes and roils like water in a pan on a hot stove. The outer core also has "hurricanes"--whirlpools powered by the Coriolis forces of Earth's rotation. These complex motions generate our planet's magnetism through a process called the dynamo effect.
Using the equations of magnetohydrodynamics, a branch of physics dealing with conducting fluids and magnetic fields, Glatzmaier and colleague Paul Roberts have created a supercomputer model of Earth's interior. Their software heats the inner core, stirs the metallic ocean above it, then calculates the resulting magnetic field. They run their code for hundreds of thousands of simulated years and watch what happens.
What they see mimics the real Earth: The magnetic field waxes and wanes, poles drift and, occasionally, flip. Change is normal, they've learned. And no wonder. The source of the field, the outer core, is itself seething, swirling, turbulent. "It's chaotic down there," notes Glatzmaier. The changes we detect on our planet's surface are a sign of that inner chaos.
They've also learned what happens during a magnetic flip. Reversals take a few thousand years to complete, and during that time--contrary to popular belief--the magnetic field does not vanish. "It just gets more complicated," says Glatzmaier. Magnetic lines of force near Earth's surface become twisted and tangled, and magnetic poles pop up in unaccustomed places. A south magnetic pole might emerge over Africa, for instance, or a north pole over Tahiti. Weird. But it's still a planetary magnetic field, and it still protects us from space radiation and solar storms.
And, as a bonus, Tahiti could be a great place to see the Northern Lights. In such a time, Larry Newitt's job would be different. Instead of shivering in Resolute Bay, he could enjoy the warm South Pacific, hopping from island to island, hunting for magnetic poles while auroras danced overhead.
Sometimes, maybe, a little change can be a good thing.
ScienceDaily (Dec. 9, 2005)
After some 400 years of relative stability, Earth's North Magnetic Pole has moved nearly 1,100 kilometers out into the Arctic Ocean during the last century and at its present rate could move from northern Canada to Siberia within the next half-century.
If that happens, Alaska may be in danger of losing one of its most stunning natural phenomena - the Northern Lights.
But the surprisingly rapid movement of the magnetic pole doesn't necessarily mean that our planet is going through a large-scale change that would result in the reversal of the Earth's magnetic field, Oregon State University paleomagnetist Joseph Stoner reported today at the annual meeting of the American Geophysical Union in San Francisco, Calif.
"This may be part of a normal oscillation and it will eventually migrate back toward Canada," said Stoner, an assistant professor in OSU's College of Oceanic and Atmospheric Sciences. "There is a lot of variability in its movement."
Calculations of the North Magnetic Pole's location from historical records goes back only about 400 years, while polar observations trace back to John Ross in 1838 at the west coast of Boothia Peninsula. To track its history beyond that, scientists have to dig into the Earth to look for clues.
Stoner and his colleagues have examined the sediment record from several Arctic lakes. These sediments - magnetic particles called magnetite - record the Earth's magnetic field at the time they were deposited. Using carbon dating and other technologies - including layer counting - the scientists can determine approximately when the sediments were deposited and track changes in the magnetic field.
The Earth last went through a magnetic reversal some 780,000 years ago. These episodic reversals, in which south becomes north and vice versa, take thousands of years and are the result of complex changes in the Earth's outer core. Liquid iron within the core generates the magnetic field that blankets the planet.
Because of that field, a compass reading of north in Oregon will be approximately 17 degrees east from "true geographic north." In Florida, farther away and more in line with the poles, the declination is only 4-5 degrees west.
The Northern Lights, which are triggered by the sun and fixed in position by the magnetic field, drift with the movement of the North Magnetic Pole and may soon be visible in more southerly parts of Siberia and Europe - and less so in northern Canada and Alaska.
In their research, funded by the National Science Foundation, Stoner and his colleagues took core samples from several lakes, but focused on Sawtooth Lake and Murray Lake on Ellesmere Island in the Canadian Arctic. These lakes, about 40 to 80 meters deep, are covered by 2-3 meters of ice. The researchers drill through the ice, extend their corer down through the water, and retrieve sediment cores about five meters deep from the bottom of the lakes.
The 5-meter core samples provide sediments deposited up to about 5,000 years ago. Below that is bedrock, scoured clean by ice about 7,000 to 8,000 years ago.
"The conditions there give us nice age control," Stoner said. "One of the problems with tracking the movement of the North Magnetic Pole has been tying the changes in the magnetic field to time. There just hasn't been very good time constraint. But these sediments provide a reliable and reasonably tight timeline, having consistently been laid down at the rate of about one millimeter a year in annual layers.
"We're trying to get the chronology down to a decadal scale or better."
What their research has told Stoner and his colleagues is that the North Magnetic Pole has moved all over the place over the last few thousand years. In general, it moves back and forth between northern Canada and Siberia. But it also can veer sideways.
"There is a lot of variability in the polar motion," Stoner pointed out, "but it isn't something that occurs often. There appears to be a 'jerk' of the magnetic field that takes place every 500 years or so. The bottom line is that geomagnetic changes can be a lot more abrupt than we ever thought."
Shifts in the North Magnetic Pole are of interest beyond the scientific community. Radiation influx is associated with the magnetic field, and charged particles streaming down through the atmosphere can affect airplane flights and telecommunications.
SOURCE: Science Daily
Image reflects the SAA at approximately 560Km.
The South Atlantic Anomaly (SAA) refers to the area where the Earth's inner Van Allen radiation belt comes closest to the Earth's surface. This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher than usual levels of radiation. The effect is caused by the non-concentricity of the Earth and its magnetic dipole, and the SAA is the near-Earth region where the Earth's magnetic field is weakest.
Position and shape
The Van Allen radiation belts are symmetric with the Earth's magnetic axis, which is tilted with respect to the Earth's rotational axis by an angle of ~11 degrees. The intersection between the magnetic and rotation axes of the Earth is located ~500 kilometres (300 mi) more to the North, above the centre of the Earth. Because of this tilt and translation, the inner Van Allen belt is closest to the Earth's surface over the south Atlantic ocean, and farthest from the Earth's surface over the north Pacific ocean.
noting the point where the South Atlantic Anomaly occurs
The shape of the SAA changes over time. Since its initial discovery in 1958, the southern limits of the SAA have remained roughly constant while a long-term expansion has been measured to the northwest, the north, the northeast, and the east. Additionally, the shape and particle density of the SAA varies on a diurnal basis, with greatest particle density corresponding roughly to local noon. At an altitude of approximately 500 km (300 mi), the SAA spans from -50° to 0° geographic latitude and from -90° to +40° longitude. The highest intensity portion of the SAA drifts to the west at a speed of about 0.3 degrees per year, and is noticeable in the references listed below. The drift rate of the SAA is very close to the rotation differential between the Earth's core and its surface, estimated to be between 0.3 and 0.5 degrees per year.
Current literature suggests that a slow weakening of the geomagnetic field is one of several causes for the changes in the borders of the SAA since its discovery. As the geomagnetic field continues to weaken, the inner Van Allen belt gets closer to the Earth, with a commensurate enlargement of the SAA at given altitudes. Some scientists, including Dr. Pieter Kotze, head of the geomagnetism group at the Hermanus Magnetic Observatory in the southern Cape, believe that the anomaly is a side effect of geomagnetic reversal.
Predictions estimate that by 2240 the SAA may cover approximately half of the southern hemisphere
The South Atlantic Anomaly is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation, caused by the trapped protons in the inner Van Allen belt, each time. The International Space Station, orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem. The Hubble Space Telescope does not take observations while passing through the SAA. Astronauts are also affected by this region which is said to be the cause of peculiar 'shooting stars' seen in the visual field of astronauts. Passing through the South Atlantic Anomaly is thought to be the reason for the early failures of the Globalstar network's satellites.
NASA has reported that modern laptops have crashed when the space shuttle flights passed though the anomaly.
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