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Abstract

The modelling of the ocean global circulation induced magnetic eld is aected by various uncertainties that originate from errors in the input data and from the model itself. The amount of aggregated uncertainties and their eect on the modelling of electromagnetic induction in the ocean is unknown. For many applications, however, the knowledge of uncertainties in the modelling is essential, e.g. data assimilation. To investigate the uncertainty in the modelling of motional induction at the sea surface, ensemble simulations are performed on the basis of dierent error scenarios and error covariance matrices. This ensemble-based approach allows to estimate both the spatial distribution and temporal variation of the uncertainty in the ocean induced magnetic eld. The largest uncertainty in the ocean induced magnetic eld occurs in the area of the Antarctic Circumpolar Current. Local maxima reach values of up to 0.7 nano Tesla. The estimated global annual mean uncertainty in the ocean induced magnetic eld ranges from 0.1 to 0.4 nT. The relative amount of uncertainty reaches up to 30% of the signal strength with largest values in regions in the northern hemisphere. The major source of uncertainty is found to be introduced by wind stress from the atmospheric forcing of the ocean model. In addition, the temporal evolution of the uncertainty in the induced magnetic eld shows distinct seasonal variations. Specic regions are identied which are robust with respect to the introduced uncertainties.