Cumulative impacts refer to the combined effects of multiple stressors on an ecosystem, e.g., climate change, pollution, and fishing. They are one of the biggest threats to ecosystems and biodiversity, but understanding them better remains a grand challenge in marine ecology. Modeling is a crucial component of tackling this challenge. However, current modeling approaches contradict empirical studies, suffer from data limitations, and ignore the statistical possibilities arising when ecosystem simulations are repeated many 1,000 times. New modeling and analysis approaches are therefore needed. The Norwegian Research Council FRIPRO project CLIMAX aims to make a leap in the modeling of cumulative impacts and exploit this methodological progress to understand how cumulative impacts emerge at the ecosystem scale. Specifically, we ask: 1) How might stressor interactions at the ecosystem scale emerge from known effects on individual species? 2) How do chronic stressors affect ecological resilience to short-term, extreme disturbances like marine heatwaves