Surge history and dynamics of Fisher Glacier, Yukon, 1948–2022

Abstract Remotely sensed datasets indicate that Fisher Glacier underwent two surges since 1948: during approximately 1969–72 and 2013–16. These were characterized by an advanced terminus position (terminus-wide average advance 571 ± 143 m from 1963 to 1972 and 868 ± 8 m from 2014 to 2017), intense surface crevassing (up to >30 km up-glacier from the terminus during both surges), high surface velocities and a down-glacier transfer of mass. The intervening quiescent phase lasted for 40 years, during which velocities were generally low (<50 m a −1 ), but underwent a slow multidecadal increase starting around 1985, spreading from the middle of the glacier. A pre-surge buildup phase beginning around 2008 resulted in velocities of up to ∼200 m a −1 . The active phase of the surge initiated in winter 2013/14, with velocities of up to 1500 m a −1 propagating both up- and down-glacier from the mid-glacier region. In July 2016, the surge rapidly terminated within a period of ∼1 month. Characterized by a rapid onset and termination, but also displaying a multidecadal acceleration prior to the surge, the cause of Fisher Glacier’s surges may be best explained by a unifying framework such as the enthalpy balance theory.