How does water shape our lives? By exploring the functions of the hydrosphere through stable isotopes and a first-order flow model of ice cores, this research helps uncover what happened to Earth’s climate in the past and hence helps predict what might happen in the future. In this Keystone I transport you to the icy record books stored in the Taku Glacier located in Southeastern Alaska. My Keystone fills a 2400-year gap in the climate record for this region with a glacial flow model and timescale based on research I conducted with the Juneau Icefield Research Program.