Multi-Year Ice Dynamics at Køge Bugt Central Glacier Controlled by Bed Topography

Køge Bugt Central (KBC) is Greenland's fourth largest outlet glacier in terms of ice discharge. However, the drivers behind its substantial multi-year variations in ice dynamics remain unknown. In this study, we use remotely sensed data sets of ice surface velocity, ice surface elevation, ice discharge, and terminus position, in combination with modeled estimates of surface runoff and ocean thermal forcing, to explore variations in its ice dynamics between 2016 and 2024. Our results indicate that KBC functions as a self-organizing system, whereby an underlying bedrock ridge serves as a critical pinning point around which it oscillates. Terminus retreat occurs when the glacier reaches a super-critical state, with strong evidence for buoyancy-driven calving observed. Whilst KBC is currently stabilized by the bedrock ridge, sustained thinning will eventually remove this critical control on ice flow, likely initiating a fundamental shift in ice dynamics and rendering KBC more susceptible to future climatic change.