Persistent Magnetic Fields from Subsea HVAC Cables: A Revised Empirical Model

As offshore power grids expand, subsea cables are emerging as the dominating source of magnetic fields (B-fields) in the marine environment. Current models often underestimate their reach, suggesting a decrease only within a few metres from the cable. Here we present a new model, grounded in field data, that faithfully represent the B-fields generated by High Voltage Alternating Current export cables. Incorporating an empirically derived component which dominates in the far-field region, our model shows that these B-fields can extend almost 100 metres from the cable, an eightfold increase over previous estimates. These findings i) raise concern for magneto-sensitive species, highlighting the need for improved environmental risk assessments modelling, and ii) challenge the effectiveness of twisting cable to mitigate B-fields emissions, with clear implications for cable engineering and installation costs. Attention must now shift on a better understanding of the power transmission, ensuring environmental sustainability to the renewable energy expansion.