Williams Joshua J, Gourmelen Noel, Nienow Peter
School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK.
Sci Rep. 2020 Feb 3;10(1):1647. doi: 10.1038/s41598-020-58355-2.
The subglacial hydrological system critically controls ice motion at the margins of the Greenland Ice Sheet. However, over multi-annual timescales, the net impact of hydro-dynamic coupling on ice motion remains poorly understood. Here, we present annual ice velocities from 1992-2019 across a ~10,600 km land-terminating area of southwest Greenland. From the early-2000s through to ~2012, we observe a slowdown in ice motion in response to increased surface melt, consistent with previous research. From 2013 to 2019 however, we observe an acceleration in ice motion coincident with atmospheric cooling and a ~15% reduction in mean surface melt production relative to 2003-2012. We find that ice velocity speed-up is greater in marginal areas, and is strongly correlated with ice thickness. We hypothesise that under thinner ice, increases in basal water pressure offset a larger proportion of the ice overburden pressure, leading to reduced effective pressure and thus greater acceleration when compared to thicker ice further inland. Our findings indicate that hydro-dynamic coupling provides the major control on changes in ice motion across the ablation zone of land terminating margins of the Greenland Ice Sheet over multi-annual timescales.
冰下水文系统对格陵兰冰原边缘的冰运动起着至关重要的控制作用。然而，在多年时间尺度上，水动力耦合对冰运动的净影响仍知之甚少。在此，我们展示了1992年至2019年格陵兰西南部约10600公里陆地末端区域的年冰速。从21世纪初到2012年左右，我们观察到冰运动因表面融化增加而放缓，这与之前的研究一致。然而，从2013年到2019年，我们观察到冰运动加速，同时大气冷却，且相对于2003 - 2012年，平均表面融化量减少了约15%。我们发现边缘区域的冰速加快更为明显，且与冰厚度密切相关。我们推测，在较薄的冰层下，底部水压的增加抵消了更大比例的冰覆盖压力，导致有效压力降低，因此与内陆较厚的冰层相比，加速度更大。我们的研究结果表明，在多年时间尺度上，水动力耦合对格陵兰冰原陆地末端边缘消融区的冰运动变化起主要控制作用。
