Abstract
<jats:p> Moulins on the southwestern Greenland Ice Sheet (GrIS) can drain large volumes of surface meltwater to the base of the ice sheet in summer, affecting basal water pressures and ice motion. However, the spatiotemporal moulin distributions (including numbers, densities and locations) and the drainage-versus-storage competition between moulins and terminal lakes (two outlet types of internally drained catchments) remain unclear. We manually map moulins and terminal lakes on the southwestern GrIS and analyze their interannual distributions during late summer 2016-2021 using Sentinel-2 images and ArcticDEM. Our findings include: (1) moulin numbers vary significantly with an annual mean of 346, ranging from 264 to 418 (densities of 0.02–0.03 km <jats:sup>-2</jats:sup> ), and stronger meltwater runoff induces more moulins; (2) moulins drain 91.7% of surface meltwater runoff on average and up to 97.8% in the warm 2016; (3) stable moulins (recur ≥4 in 6 years) account for ~60% of moulins on average, and drain ~70% of surface meltwater runoff; (4) terminal lakes increase in number as runoff decreases, storing 8.3% of surface meltwater runoff on average and 21.0% in the cool 2017; (5) the majority of moulins (~66%) and terminal lakes (~99%) can be captured by surface topographic depressions modeled by ArcticDEM, whereas >70% of topographic depressions contain neither of these features. In summary, this study produces multi-year moulin maps on the southwestern GrIS, and reveals that moulins are denser in stronger-melting years with higher percentages of meltwater drainage into the ice sheet, thereby providing new constraints for the GrIS hydrological models. </jats:p>