Rapid Grounding Line Retreat of Ryder Glacier, Northern Greenland, from 1992 to 2021

Ice losses from the Greenland Ice Sheet (GrIS) have expanded rapidly in recent decades. The Ryder Glacier (RG) is one of the major marine-terminating outlet glaciers located on the northwestern GrIS. Paying attention to its dynamic changes is of great significance to the study of the mass balance in the whole GrIS. We utilize the Double Differential Synthetic Aperture Radar Interferometry (DDInSAR) to detect the change of grounding line (GL) position in RG from 1992 to 2021. It is found that the GL has retreated significantly (1-8 km) during this period and its rate on the eastern and western flanks is nearly eight times different. To explore the reasons for the retreat, we combine the ice-shelf thickness variation, surface and bed topography, and potential subglacial drainage-pathway to discover that the basal melt governs the severe migration in RG. The uneven melting dominates the asymmetric retreat on the eastern and western flanks, which is caused by the disparity of ocean heat near the GL at different depths and the bed topography slope. The higher the ocean heat and the greater the slope are, the more intense the basal melt is, leading to further GL retreat and threatening the stability of the ice shelf. The experimental results also demonstrate that RG may continue to retreat, with a more drastic change in the west, in the coming decades.