Quantifying meltwater refreezing along a transect of sites on the Greenland ice sheet
Quantifying meltwater refreezing along a transect of sites on the Greenland ice sheet
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DOI：
10.5194/tc-9-691-2015
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发表时间：
2015-01-01
期刊：
影响因子：
5.2
通讯作者：
Harper, J.
中科院分区：
文献类型：
--
作者：
Cox, C.;Humphrey, N.;Harper, J.
在格陵兰冰盖上，大量的表面融水在积雪中重新冻结，造成表面质量平衡估计的不确定性。这种重新冻结有可能缓冲季节性径流，以应对未来融化的增加，但直接测量这一过程仍然很困难。我们提出了一种方法，用于量化再冻结在点位置使用原位积雪温度观测。从2007年至2009年沿着格陵兰累积区11个站点的一个样带的两个融化季节的过程中，收集了亚小时积雪温度剖面的时间序列。温度剖面的季节性变化与基于高时间分辨率温度梯度的热通量估计相结合，使我们能够利用能量守恒来隔离再冻结释放的热量。我们的方法进行了验证，从冬季数据时，没有再冻结发生，估计使用蒙特卡罗技术的不确定性。虽然我们将我们的方法限制在1米和10米深度之间的一个子部分，但我们的重新冻结估计似乎与基于模型的估计有很大不同。此外，结果表明，大量的再冻结发生在深度大于1米，融水的横向迁移显着复杂的总表面熔体和总再冻结之间的关系。
On the Greenland ice sheet, a significant quantity of surface meltwater refreezes within the firn, creating uncertainty in surface mass balance estimates. This refreezing has the potential to buffer seasonal runoff to future increases in melting, but direct measurement of the process remains difficult. We present a method for quantifying refreezing at point locations using in situ firn temperature observations. A time series of sub-hourly firn temperature profiles were collected over the course of two melt seasons from 2007 to 2009 along a transect of 11 sites in the accumulation zone of Greenland. Seasonal changes in temperature profiles combined with heat flux estimates based on high-temporal-resolution temperature gradients enable us to isolate the heat released by refreezing using conservation of energy. Our method is verified from winter data when no refreezing takes place, and uncertainty is estimated using a Monte Carlo technique. While we limit our method to a subsection of firn between depths of 1 and 10 m, our refreezing estimates appear to differ significantly from model-based estimates. Furthermore, results indicate that a significant amount of refreezing takes place at depths greater than 1 m and that lateral migration of meltwater significantly complicates the relationship between total surface melt and total refreezing.