The earth's geomagnetic field and geolocation of fish:first results of a new approach

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Today’s EMF can be described through satellite measurement derived field models (IGRF - International Geomagnetic Reference Field, Figure 1.) The EMF is described by the magnetic elements, visualized in Figure 2. By choosing appropriate elements observed at a given locality, it is in principle possible to determine the geographic position of this locality by comparing these values with the IGRF (see Figure 1). By measuring and storing magnetic element-readings from a registration tag attached to a fish, recovering the tag will potentially enable tracking the migration pattern. The earth is immersed in its EMF – consequently the proposed concept may be applied globally. Limitations of the concept: The EMF varies in a broad range of time-scales. For the present purpose, only short time variations are important (Figure 3). Registered magnetic element-readings must hence be corrected for these variations. For the north Atlantic, time variations of magnetic elements can be obtained from numerous magnetic observatories (Iceland, Norway, etc). The proposed concept will only be applicable in regions where isolines of magnetic elements are close to orthogonal. We have used Z and H, which are “suitable” off the coast of northern Norway/Barents Sea, but less so off the western coast of Norway (Fig. 1).