Spatial and temporal melt variability at Helheim Glacier, East Greenland, and its effect on ice dynamics
Spatial and temporal melt variability at Helheim Glacier, East Greenland, and its effect on ice dynamics
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DOI：
10.1029/2010jf001760
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发表时间：
2010-12-29
影响因子：
3.9
通讯作者：
Dahl-Jensen, D.
中科院分区：
文献类型：
--
作者：
Andersen, M. L.;Larsen, T. B.;Dahl-Jensen, D.
了解格陵兰冰盖大型注水冰川的行为对于评估气候变化对海平面上升的影响至关重要。海洋终止出口冰川的流量部分受到终点处发生的崩解相关过程的控制，但也受到通过冰臼、裂缝和其他路径向河床排水的地表径流的影响。为了研究后一种影响的程度，我们为东格陵兰赫尔海姆冰川开发了一个分布式表面能量平衡模型，以计算地表融化，从而估算径流。该模型由 2007 年和 2008 年夏季在冰川上运行的自动气象站的数据驱动，并通过独立的消融测量进行校准。模型融化在部署期间相对于平均值变化高达 68%，冰川树干下游的融化速率比上部冰川高约 77%。我们将夏季融化的变化与全球定位系统调查得出的表面速度估计值进行比较。在冰川前部附近，径流变化（根据地表融化估算）和速度变化之间存在显着相关性（>95% 的水平），速度相对于融化有 1 天的延迟。尽管与之前在一些崩解事件后观察到的加速度相比，速度变化很小，但我们的研究结果表明，赫尔海姆冰川的流速对径流的变化很敏感。这种反应在崩解前缘附近有严重裂缝、快速移动的区域最为显着。互相关函数峰值的延迟意味着地表径流到达河床的传输时间为 12-36 小时。
Understanding the behavior of large outlet glaciers draining the Greenland Ice Sheet is critical for assessing the impact of climate change on sea level rise. The flow of marine-terminating outlet glaciers is partly governed by calving-related processes taking place at the terminus but is also influenced by the drainage of surface runoff to the bed through moulins, cracks, and other pathways. To investigate the extent of the latter effect, we develop a distributed surface-energy-balance model for Helheim Glacier, East Greenland, to calculate surface melt and thereby estimate runoff. The model is driven by data from an automatic weather station operated on the glacier during the summers of 2007 and 2008, and calibrated with independent measurements of ablation. Modeled melt varies over the deployment period by as much as 68% relative to the mean, with melt rates approximately 77% higher on the lower reaches of the glacier trunk than on the upper glacier. We compare melt variations during the summer season to estimates of surface velocity derived from global positioning system surveys. Near the front of the glacier, there is a significant correlation (on >95% levels) between variations in runoff (estimated from surface melt) and variations in velocity, with a 1 day delay in velocity relative to melt. Although the velocity changes are small compared to accelerations previously observed following some calving events, our findings suggest that the flow speed of Helheim Glacier is sensitive to changes in runoff. The response is most significant in the heavily crevassed, fast-moving region near the calving front. The delay in the peak of the cross-correlation function implies a transit time of 12-36 h for surface runoff to reach the bed.