Remote Magnetism

Researchers Offer New Technique to Explore Earth's Magnetic Field

A pair of Scripps geophysicists has taken to the skies to explore the deep earth in a novel way.

Scripps Institution of Oceanography at UC San Diego researchers Jeff Gee and Steve Cande and a colleague from Rutgers University are complementing traditional research methods with unmanned airborne vehicles (UAVs) to improve scientists ability to map fluctuations in Earth s magnetic field. By testing new ways to collect this valuable data, they will be better equipped to understand past fluctuations of the field.

Fluctuations in the magnetic field are a normal phenomenon.  Scientists have uncovered fluctuations of varying intensity as well as complete reversals in the orientation of Earth's magnetic polarities, which causes the positions of magnetic north and magnetic south to flip-flop.  Current observations show a lessening of the magnetic field's intensity.

"It's decreasing at a pretty good clip," said Gee.

In an effort to better understand how Earth s geomagnetic field works, Gee and his colleagues are studying the Cretaceous Quiet Zone (KQZ), a unique period where no magnetic reversals occurred, in order to better understand how the magnetic field varies when the polarity is constant.

The KQZ, a 37-million- year interval, which occurred from 121 to 83 million years ago, is a period of constant normal polarity when about one quarter of the present seafloor was generated, thus preserving unique geomagnetic records. The UAVs are helping scientists collect new evidence that the KQZ may not have been as quiet as originally thought. Variations in the magnetic field have been detected during the KQZ and the collection of magnetic anomaly data is vital to investigate these intervals of past geomagnetic field behavior.

"If we were to find that the KQZ did not have such fluctuations, or if they were bigger or smaller, that will ultimately tell us how the geomagnetic field works," said Gee.

To evaluate the origin of the anomalies within the KQZ, the scientists conducted a survey in a remote area of the southwest Pacific on Scripps s R/V Melville using traditional surface towed magnetometer methods as well as UAVs. During the 2007 cruise, the research team deployed the first UAVs from a University-National Oceanographic Laboratory System (UNOLS) research vessel. The Georanger UAVs, operated by Fugro Airborne and equipped with a high-resolution magnetometer, collected magnetic data at an elevation of approximately 200m while the research vessel collected bathymetric and sea surface magnetic data.
These nine deployments, each averaging about 11 hours, provided more than 10,000 kilometers (6,200 miles) of magnetic data, which is more than was acquired by the ship during the month-long cruise, said Gee.

Based on the success of this study, Gee anticipates that UAVs will play an increasingly important role in a variety of marine research programs and locations where collecting data has proved difficult using current techniques.
 
  --Annie Reisewitz