Rapid reconfiguration of the Greenland Ice Sheet margin

The Greenland Ice Sheet has lost mass at an accelerating rate over the last two decades, but limits of early remote sensing restricted examination of localized change at an ice-sheet-wide scale. We use satellite-derived ice-sheet surface velocities, glacier terminus advance/retreat, and surface elevation-change data spanning ~1985-2015 to explore local characteristics of what is now a rapid reconfiguration of the ice sheet coastal margin. Widespread glacier terminus retreat is a more consistent climate response indicator than surface velocities, though local velocity patterns provide indicators of ice flow reconfiguration, including narrowing zones of fast-flow, ice flow rerouting, and outlet abandonment. The implications of this observed rapid reconfiguration are wide-ranging, and likely include alteration of subglacial hydrology, iceberg discharge, liquid freshwater flux, potential nutrient and sediment flux, and mass flux. Without detailed observations of earlier deglaciations and with present limits on ice-sheet model capabilities, these observational records provide an important analogue for past deglaciation and for projecting future ice loss.

过去二十年间，格陵兰冰盖（Greenland Ice Sheet）的冰量损失速率持续加快，但早期遥感技术的局限性制约了冰盖全域尺度下的局地变化研究。本研究采用跨度约1985年至2015年的卫星反演冰盖表面流速、冰川末端进退数据以及表面高程变化数据，探究当前冰盖沿海边缘快速重构的局地特征。尽管局地流速格局可作为冰流重构的指示标志，涵盖快速流动带收窄、冰流改道与出水口废弃，但全域普遍的冰川末端退却，仍是比表面流速更具一致性的气候响应指标。本次观测到的快速重构所带来的影响范围广泛，很可能涉及冰下水文（subglacial hydrology）系统改变、冰山排放（iceberg discharge）、液态淡水通量（liquid freshwater flux）、潜在营养物质与沉积物通量（nutrient and sediment flux）以及质量通量（mass flux）的变化。由于缺乏针对早期冰消作用（deglaciation）的详细观测资料，且当前冰盖模型（ice-sheet model）的性能仍存在局限，这些观测记录可为既往冰消过程的研究以及未来冰量损失的预测提供重要的类比参考（analogue）。