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Meltwater percolation, impermeable layer formation and runoff buffering on Devon Ice Cap, Canada
Journal of Glaciology ( IF 3.4 ) Pub Date : 2019-11-08 , DOI: 10.1017/jog.2019.80
David W. Ashmore , Douglas W. F. Mair , David O. Burgess

The retention of meltwater in the accumulation area of the Greenland ice sheet and other Arctic ice masses buffers their contribution to sea level change. However, sustained warming also results in impermeable ice layers or ‘ice slabs’ that seal the underlying pore space. Here, we use a 1-D, physically based, high-resolution model to simulate the surface mass balance (SMB), percolation, refreezing, ice layer formation and runoff from across the high-elevation area of Devon Ice Cap, Canada, from 2001 to 2016. We vary the thickness of the ‘impermeable’ ice layer at which underlying firn becomes inaccessible to meltwater. Thick near-surface ice layers are established by an initial deep percolation, the formation of decimetre ice layers and the infilling of interleaving pore space. The cumulative SMB increases by 48% by varying impermeable layer thickness between 0.01 and 5 m. Within this range we identify narrower range (0.25–1 m) that can simulate both the temporal variability in SMB and the observed near-surface density structure. Across this range, cumulative SMB variation is limited to 6% and 45–49% of mass retention takes place within the annually replenished snowpack. Our results indicate cooler summers after intense mid-2000s warming have led to a partial replenishment of pore space.

中文翻译:

加拿大德文冰盖上的融水渗透、不透水层形成和径流缓冲

格陵兰冰盖和其他北极冰块积聚区的融水滞留缓冲了它们对海平面变化的影响。然而,持续变暖也会导致不透水的冰层或“冰板”密封下面的孔隙空间。在这里,我们使用一维、基于物理的高分辨率模型来模拟加拿大德文冰帽高海拔地区的表面质量平衡 (SMB)、渗流、再冻结、冰层形成和径流。 2001 年至 2016 年。我们改变了“不透水”冰层的厚度,在这些冰层下,融水无法进入。厚的近地表冰层是由初始的深层渗流、分米冰层的形成和交错孔隙空间的充填形成的。通过在 0.01 和 5 m 之间改变不渗透层厚度,累积 SMB 增加了 48%。在这个范围内,我们确定了更窄的范围(0.25-1 m),可以模拟 SMB 的时间变化和观察到的近地表密度结构。在这个范围内,累积的 SMB 变化被限制在 6% 和 45-49% 的质量保留发生在每年补充的积雪中。我们的结果表明,在 2000 年代中期剧烈变暖之后,夏季凉爽导致孔隙空间部分补充。
更新日期:2019-11-08
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