1 Department of Building, Civil, and Environmental Engineering, Concordia University, Montreal, Quebec, Canada.
2 Department of Building, Civil, and Environmental Engineering, Concordia University, Montreal, Quebec, Canada. Electronic address: zhi.chen@concordia.ca.
3 Kenneth Lee Research Inc., Halifax, Nova Scotia, Canada.

Oil pollution is a growing environmental concern due to its detrimental effect on the marine ecosystem. Rapid prediction of oil spill fate during emergency response can help responders make informed management decisions. However, instant access to reliable environmental data may be challenging, as most oil weathering models lack compatible database for prompt input. In this study, a GIS-based offshore oil spill management toolkit (GOOSM) was developed to support decision-making in oil spill response, which consisted of an oil fate module, a response simulator, an oil database, and a global environment database. The new tool was verified through comparison with an established oil spill model, GNOME, yielding highly consistent results of oil mass balance and properties. GOOSM was also applied to perform a hindcast of the Exxon Valdez (EV) oil spill and wave tank experiments. The validation results for oil properties showed an acceptable error range for emulsion viscosity and an accurate simulation of oil density. Numerical experiments were conducted using both GNOME and GOOSM to examine the impact of start-up time on dispersant effectiveness. The results demonstrated the GOOSM's capability to capture the window of opportunity for dispersant use, highlighting its potential to enhance the accuracy and timeliness of operational oil spill response. This decision-support tool enables short-term forecasting of oil fate and response outcomes in marine environments globally.