In this JAVA-based interactive modeling activity, students are introduced to the concepts of mass balance, flow rates, and equilibrium using a simple water bucket model. Students can vary flow rate into the bucket, initial water level in the bucket, and residence time of water in the bucket. After running the model, the bucket's water level as a function of time is presented graphically and in tabular form.

Students gain experience using a spreadsheet and working with others to decide how to conduct their model 'experiments' with the NASA GEEBITT (Global Equilibrium Energy Balance Interactive Tinker Toy). This activity helps students become more familiar with the physical processes that made Earth's early climate so different from that of today. Students also acquire first-hand experience with a limitation in modeling, specifically, parameterization of critical processes.

In this activity for undergraduate students, learners build a highly simplified computer model of thermohaline circulation in the North Atlantic Ocean and conduct a set of simulation experiments to understand the complex dynamics inherent in this simple model.