## 6 Discussion and Conclusions  
This article presents a DES-based approach to predict the operating performance of the FSWNS under different operating scenarios. The approach is validated against real-world data on maritime traffic in the Bothnian Bay in the period 15 January-15 February 2010. In terms of the number of ship arrivals per port, representing the transport capacity of the FSWNS, the simulation agrees well with the data. In terms of the number of instances of IB assistance and IB waiting times, the standard deviations between the averages of 35 independent simulation runs and the data are 13% and 18%, respectively. For each of the simulated metrics, the data fall within an approximated 95% confidence interval. These findings indicate that the proposed DES-based approach can capture the complex behavior of the FSWNS and roughly estimate its operating performance. Due to various identified knowledge and data gaps, as well as due to technical limitations of the applied simulation approach, the simulation model is based on generalized assumptions concerning convoy operations (a maximum of two ships are assisted by an IB at a time), IB transfer times (probabilistically determined), criteria for providing IB assistance (generalized criteria), and assumptions concerning the presence of brash ice channels (generalized assumptions), among others. A sensitivity analysis indicates that the simulated number of instances of IB assistance and IB waiting times are particularly sensitive to assumptions concerning the presence of brash ice channels. Future research is needed to address the limitations. Considering the present limitations, the proposed approach appears best suited for scenario-based assessments in which the performance of the FSWNS is assessed for a limited period (e.g., one month) with heavy ice conditions during which the main shipping routes can be assumed fixed. The outcome of such a scenario-based assessment may indicate whether the capacity of the FSWNS under the simulated conditions is sufficient to keep the system in \"balance\". Case studies were carried out in which the approach was applied to assess the impact of replacing various percentages of the present fleet of merchant ships entering the Bay of Bothnia by EEDI-compliant ships. In a scenario in which around one-third of the current fleet is replaced by EEDI-compliant ships, the simulation outcome indicates that the number of cases of IB assistance is increased from 222 to 328 (+48%) and that the cumulated waiting times for IB assistance is increased from 775 h to 1378 h (+78%). In another scenario in which around two-thirds of the current fleet is replaced with EEDI-compliant ships, the simulation outcome indicates that the total number of cases of IB assistance is increased from 222 to 497 (+116%) and that the cumulated waiting times for IB assistance is increased from 775 h to 5157 h (+565%). For the considered scenarios, simulation outcomes indicate that the predicted increase in IB waiting times can be largely mitigated if the number of IBs operating in the area is increased from 4 to 5 or from 4 to 6, respectively. However, due to a lack of detailed data on, e.g., how the EEDI would influence the ice-going capability and other technical characteristics of the affected merchant fleet, the outcome of the analysis is not conclusive. In summary, the presented approach, which is one of the first attempts to simulate the FSWNS, may provide new insights into the behavior and performance of the FSWNS under different operating scenarios, considering a multitude of interlinked and self-reinforcing system behaviors. As such, the method may be used to support decision-making concerning the management of the FSWNS to meet future goals concerning operational efficiency. In the future, a potential further developed version of the model could be used for more holistic analyses, e.g., to analyze the cost- and energy-efficiency of the FSWNS, considering e.g., the impacts of climate change on sea ice conditions. M.B.