A quantum computer, constructed with quantum bits, or qubits, would have capabilities beyond what is possible for conventional, classical computers. Trapped ions are a promising platform for this type of system and the path forward involves designing traps that can be micro-fabricated and customized. While traps are becoming more complex, there are challenges to maintaining high fidelity operations while continuing to scale; one major challenge is excess electric-field noise that can decohere information during entanglement operations. Despite a decade of intensive research neither the general behaviour, nor the origin of the electric-field noise in surface traps is well understood. We engineer a unique system operating in a new high-temperature regime and use it to find evidence of defect dynamics causing surface noise. We explain our results with a simple model linking our findings to a large body of work on noise in solid-state physics, providing insight into microscopic mechanisms and paths towards solving electric-field noise in ion traps.