Mapping moulins on the southwestern Greenland Ice Sheet

Moulins are vertical meltwater pathways formed by hydro-fracturing of crevasses or supraglacial lakes. On the southwestern Greenland Ice Sheet (GrIS), moulins can efficiently drain surface meltwater into the ice sheet, drive subglacial drainage system development, control variations in subglacial water pressure, and eventually influence ice motion. Thereby, moulins are essential to understand the connection between supraglacial, englacial and subglacial drainage systems. However, most of existing studies focused on moulins in small areas or short time periods, leaving moulin spatiotemporal variations still unclear. In this study, we extracted moulins on the southwestern GrIS from 2016 to 2021 using multi-temporal Sentinel-2 satellite images and ArcticDEM, and analyzed their interannual spatiotemporal variations. Results show that: (1) Moulin distribution varies significantly in different years. In general, moulin numbers increase linearly with the rise of accumulative annual meltwater runoff, while the terminal supraglacial lake numbers decreased exponentially. (2) The annual moulin distribution can affect the distributions in subsequent years, and the smaller the intervals, the stronger the effect. (3) There are significant variations in the meltwater runoff draining into the ice sheet in different years, especially in high elevation region (>1600 m).