Recurrent surge dynamics and ongoing acceleration at Devon Ice Cap’s Southeast basin, Canadian Arctic

Abstract This study analyses the dynamics of Southeast-1 and Southeast-2 glaciers on Devon Ice Cap (1959–2024) using multiple remote sensing datasets. Sharing a common tidewater terminus, the glaciers experienced two dynamic instabilities: an 8–9-year surge in the 1970s–80s advancing the terminus by up to ∼5 km and reaching velocities of >3000 m a−1, and a multiannual acceleration of Southeast-2 beginning in the mid-2000s, suggesting the start of a new surge within that basin. This instability progressed through stepwise increments each summer and propagated up-glacier, reaching velocities over an order of magnitude above quiescent levels. In 2020–23, Southeast-2 showed dynamic thickening of ∼1–5 m a−1 within the lower ∼7.5 km and thinning in the upper trunk (∼7.5–17 km from the terminus) of <−1 m a−1, indicating down-glacier mass transfer. Long-term terminus thinning and retreat increased surface slopes and driving stress, preconditioning the glacier for instability. Seasonal velocity patterns, crevasse expansion, strain rate evolution, and modelled runoff support a hydro-thermodynamic feedback, where meltwater increasingly accesses the bed and enhances basal motion. Southeast-1 remains quiescent but may destabilise similarly to the previous surge. The short surge cycle of Southeast-2 allows the first determination of a complete quiescent phase duration (∼36–37 years) in this region.