Near-surface permeability in a supraglacial drainage basin on the Llewellyn Glacier, Juneau Icefield, British Columbia

Supraglacial channel networks link time varying melt production and meltwater routing on temperate glaciers. Such channel networks often include components of both surface transport in streams and subsurface porous flow through near-surface ice, firn or snowpack. Although subsurface transport if present will likely control network transport efficacy, it is the most poorly characterized component of the system. We present measurements of supraglacial channel spacing and network properties on the Juneau Icefield, subsurface water table height, and time variation of hydraulic characteristics including diurnal variability in water temperature. We combine these data with modeling of porous flow in weathered ice to infer near-surface permeability. Estimates are based on an observed phase lag between diurnal water temperature variations and discharge, and independently on measurement of water table surface elevation away from a stream. Both methods predict ice permeability on a 1–10 m scale in the range of 10−10–10−11 m2. These estimates are considerably smaller than common parameterizations of surface water flow on bare ice in the literature, as well as smaller than most estimates of snowpack permeability. For supraglacial environments in which porosity/permeability creation in the subsurface is balanced by porous flow of meltwater, our methods provide an estimate of microscale hydraulic properties from observations of supraglacial channel spacing.

Raw project data is available by contacting [e-mail]

冰川表层渠道网络将温度冰川的时变融水产生和融水路径联系起来。此类渠道网络通常包括溪流表面的物质运输和近地表冰、雪层或雪被中的孔隙流成分。尽管地下运输若存在则可能控制网络传输效率，但它却是系统中表征最不充分的组成部分。本研究在朱诺冰川上对冰川表层渠道间距和网络特性进行了测量，对地下水位高度进行了测量，并记录了包括日变化在内的水力学特性。我们将这些数据与风化冰中的孔隙流模型相结合，以推断近地表的渗透性。这些估算基于日间水温变化与流量之间的观测相位滞后，以及独立于溪流之外的地下水位表面高程的测量。两种方法均预测了1-10米尺度上的冰渗透性在10−10至10−11 m2的范围内。这些估算值远小于文献中常见的裸冰表面水流参数化，以及小于大多数雪被渗透性的估算。对于地下孔隙流与融水孔隙流平衡的冰川表层环境，我们的方法通过冰川表层渠道间距的观测，提供了微观尺度水力学特性的估算。

原始项目数据可通过联系[e-mail]获取。