资源环境科技发展态势分析平台

The dynamic response of High Arctic glaciers to increased runoff in a warming climate remains poorly understood. We analyze a 10-year record of continuous velocity data collected at multiple sites on Nordenskioldbreen, Svalbard, and study the connection between ice flow and runoff within and between seasons. During the melt season, the sensitivity of ice motion to runoff at sites in the ablation and lower accumulation zone drops by a factor of 3 when cumulative runoff exceeds a local threshold, which is likely associated with a transition from inefficient (distributed) to efficient (channelized) drainage. Average summer (June-August) velocities are found to increase with summer ablation, while subsequent fall (September-November) velocities decrease. Spring (March-May) velocities are largely insensitive to summer ablation, which suggests a short-lived impact of summer melt on ice flow during the cold season. The net impact of summer ablation on annual velocities is found to be insignificant.

Plain Language Summary A major uncertainty in future predictions of glacier mass loss, and the corresponding sea level rise contribution, stems from a lack of understanding of potential feedbacks between surface melt and ice motion. Melt water penetrating to the bed of a glacier facilitates fast ice motion through sliding. Whether increased melt water input induces a net long-term acceleration or deceleration of ice flow however critically depends on the interaction between melt input and transience of the subglacial drainage system at both intraseasonal and interseasonal time scales. To assess this, long-term data sets of ice motion and runoff are essential. In this study, a 10-year record of continuous velocity data, collected at multiple sites on Nordenskioldbreen in Svalbard, is presented and compared to simulated runoff. We find that the sensitivity of summer velocities to runoff drops by a factor of 3 after a runoff-induced change of drainage system morphology. While average summer motion increases with ablation, fall (September-November) motion decreases, and spring (March-May) motion appears largely insensitive to summer melt. Altogether, the net impact of increased summer melt on annual velocities is found to be negligible.