Ice cores comprise one of the most comprehensive records of Earth's past climate, extending back hundreds of thousands of years. However, disentangling the information contained in the ice cores's isotopic signal in order to retrieve information on specific atmospheric events remains challenging. In this study, the authors show how atmospheric rivers - an extreme event that changes temperatures and humidity - are imprinted in the water isotopes. The study represents a major step forward in closing the knowledge gap, by discerning the local versus large-scale drivers of the isotopic signal.