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Description

Magnets have been placed in the firn of a glacier in an area of extremely high accumulation, and relocated a year later by surface magnetometer measurements. Twenty-eight magnets have been relocated at depths up to 10.5 m. The necessary equipment is light and can be purchased off-the-shelf. The depths and horizontal positions of the magnets can be calculated from the magnetic field measurements with sufficient accuracy that the task of digging them out, or drilling to some nearby large buried markers to measure positions directly, can be avoided. The errors are analyzed theoretically, and it is found that under certain restrictions (1) the depth error caused by error in magnetic field measurement varies directly as the fourth power of the depth and inversely as the moment of the magnet, and (2) the depth error caused by error in moment varies directly as the depth and inversely as the moment. Methods for optimizing the measurement procedure are discussed. With the magnetometer and magnets that we have used, depths can be estimated to about 0.5 m at 10 m depth, and about 0.1 m at 5 m depth, or better. Higher accuracy is feasible.

Publication Date

3-17-1978

Keywords

Glaciers, Alaska, Measurement, Magnetic measurements

Handle

http://hdl.handle.net/11122/15452

Magnetic markers for glacier mass balance and velocity measurements

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