Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland
Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland
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DOI：
10.5194/tc-9-123-2015
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发表时间：
2015-01-01
期刊：
影响因子：
5.2
通讯作者：
Schwanghart, W.
中科院分区：
文献类型：
--
作者：
Clason, C. C.;Mair, D. W. F.;Schwanghart, W.
被输送到格陵兰冰盖床上的融水是通过改变有效压力和加强基础润滑来驱动不同冰层运动的。冰面速度已被证明对冰面产生的融水和冰上湖泊的排水反应迅速，这表明融水从冰上向冰下水文系统的有效转移。尽管目前正在努力改进控制表面和基本过程的模拟，但对熔体转移到床层的时间和空间演变模拟受到的关注较少。在这里，我们介绍了格陵兰岛西南部莱弗莱特冰川上用于预测冰山和湖泊排水的空间分布模拟的结果。该模型适用于2009年和2010年的消融季节，以及未来更多的融化情景。模拟的湖泊流域的时间模式与重复卫星图像的分析记录的时间模式定性地可比。模拟的融水输送到床上的时间和位置也与观测到的冰面加速的时间和空间模式很好地匹配。对于较低的集水区(<；1000 m a.s.l)来说尤其如此。其中，模型和观测都表明，冰川的发展是地表融水转移到床上的主要机制。海拔较高(例如1250-1500米)冰上湖泊的开发和排水变得越来越重要。在这些较高的海拔高度，模拟的熔体产生和随后的熔体输送到床之间的延迟与观察到的最高气温和随后的速度加速之间的延迟相匹配，而在控制模拟中，熔体到床的瞬时转移不匹配。尽管预计在未来气候变暖的情况下，冰川和湖泊排水系统的数量将会增加，但湖泊排水系统在扩大融化进入海床的面积以及使更大比例的地表融化能够到达海床方面发挥着越来越重要的作用。
Meltwater delivered to the bed of the Greenland Ice Sheet is a driver of variable ice-motion through changes in effective pressure and enhanced basal lubrication. Ice surface velocities have been shown to respond rapidly both to meltwater production at the surface and to drainage of supraglacial lakes, suggesting efficient transfer of meltwater from the supraglacial to subglacial hydrological systems. Although considerable effort is currently being directed towards improved modelling of the controlling surface and basal processes, modelling the temporal and spatial evolution of the transfer of melt to the bed has received less attention. Here we present the results of spatially distributed modelling for prediction of moulins and lake drainages on the Leverett Glacier in Southwest Greenland. The model is run for the 2009 and 2010 ablation seasons, and for future increased melt scenarios. The temporal pattern of modelled lake drainages are qualitatively comparable with those documented from analyses of repeat satellite imagery. The modelled timings and locations of delivery of meltwater to the bed also match well with observed temporal and spatial patterns of ice surface speed-ups. This is particularly true for the lower catchment (< 1000 m a.s.l.) where both the model and observations indicate that the development of moulins is the main mechanism for the transfer of surface meltwater to the bed. At higher elevations (e.g. 1250-1500 m a.s.l.) the development and drainage of supraglacial lakes becomes increasingly important. At these higher elevations, the delay between modelled melt generation and subsequent delivery of melt to the bed matches the observed delay between the peak air temperatures and subsequent velocity speed-ups, while the instantaneous transfer of melt to the bed in a control simulation does not. Although both moulins and lake drainages are predicted to increase in number for future warmer climate scenarios, the lake drainages play an increasingly important role in both expanding the area over which melt accesses the bed and in enabling a greater proportion of surface melt to reach the bed.