Intensive study of the Greenland Ice Sheet's (GrIS) subglacial drainage has been motivated by its importance for ice dynamics and for nutrient/sediment export to coastal ecosystems. This has revealed consistent seasonal development of efficient subglacial drainage in the lower ablation area. While some hydrological models show qualitative agreement with field data, conflicting evidence (both field- and model-based) maintains uncertainty in the extent and rate of efficient drainage development under thick (∼1 km) ice. Here, we present the first simultaneous time series of directly-observed subglacial drainage evolution, supraglacial hydrology and ice dynamics over 11 weeks in a large GrIS catchment. We demonstrate development of a fast/efficient subglacial drainage system extending from the margin to beneath ice >900 m thick, which then persisted with little response to highly variable moulin inputs including extreme melt events and extended periods (2 weeks) of low melt input. This efficient system evolved within ∼3 weeks at a moulin initiated when a fracture intersected a supraglacial river (rather than hydrofracture and lake drainage). Ice flow response to surface melt inputs at this site follows a pattern commonly observed in the lower GrIS ablation area, and by assuming a strong relationship between ice dynamics and subglacial hydrology, we infer that efficient subglacial drainage evolution is widespread under 900 m-thick ice in west Greenland. This time series of tracer transit characteristics through a developing and then persistent efficient drainage system provides a unique data set with which to validate and constrain existing numerical drainage system models, extending their capability for simulating drainage system evolution under current and future conditions.

格陵兰冰原（GrIS）冰川下排水的深入研究的动机是其对冰动力学和养分/沉积物向沿海生态系统的出口的重要性。这表明在较低的消融区域，有效的冰川下引流始终保持季节性发展。虽然一些水文模型显示出与实地数据的定性一致性，但相矛盾的证据（基于实地和基于模型）在厚冰（约1 km）下有效排水发展的程度和速度上仍存在不确定性。在这里，我们展示了在一个大型GrIS流域中，在11周内直接观测到的冰川下排水演化，冰上水文和冰动力学的第一个同时时间序列。我们展示了一种快速/高效的冰川下排水系统的开发，该系统从边缘延伸到厚度大于900 m的冰层以下，然后，这种情况持续存在，而对高可变红磨坊输入（包括极端融化事件和低融化输入的延长时间段（2周））的响应却很少。这种有效的系统是在约3周内由红磨坊演化而来的，当时红磨坊是一条裂缝与一条冰河相交的河流（而不是水力裂缝和湖泊排水系统）相交的地方。在该站点，冰流对地表融冰输入的响应遵循在GrIS消融区较低处通常观察到的模式，并且通过假设冰动力学与冰下水文学之间的密切关系，我们推断出有效的冰下排水演化在900 m厚冰层下广泛存在。在格陵兰西部。