Two-dimensional artificial spin-ice systems constructed from arrays of dipolar coupled monodomain magnets offer an experimental route to study the physics of frustration and a corresponding degeneracy that grows exponentially with system size. However, so far, such systems remain mainly frozen below their magnet’s Curie temperature, unable to explore their potential-energy landscape through thermal fluctuations. Here we demonstrate the creation of thermally active finite artificial spin-ice systems and the observation of magnetic fluctuations in real time and space. We show that the subsequent magnetization dynamics can be entirely understood from the underlying dipolar energy landscape, and demonstrate that both the energy scale and the complexity of the landscape affect the temporal and spatial nature of the observed configurational changes. This work paves the way for the in situ study of thermally induced magnetic relaxation processes and delivers a controlled route to the lowest-energy state in extended two-dimensional artificial spin-ice systems.