In this study, Operational Modal Analysis (OMA) is used to identify the natural frequencies and damping values of the modes of an Offshore Wind Turbine (OWT) present in the response due to the stochastic excitation of ambient loads. Estimations of the aeroelastic damping of the operational turbine modes (including the effects of the aerodynamic, hydrodynamic and soil forces) give a quantitative view of the stability characteristics of the wind turbine. Two different test cases including an overspeed stop and ambient excitation have been considered. The experimental data have been obtained during a measurement campaign on an offshore wind turbine in the Belgian North Sea and the results are compared with the numerical simulations which are implemented in HAWC2. This project is in the framework of the Flemish funded offshore wind infrastructure project.