The potential of capillary forces to retain water in pores is an important property of snow and firn at glaciers. Meltwater suspended in pores does not contribute to runoff and may refreeze during winter, which can affect the climatic mass balance and the subsurface density and temperature. However, measurement of firn water content is challenging and few values have been reported in the literature. Here, we use subsurface temperature and density measured at the accumulation zone of Lomonosovfonna (1200 m a.s.l.), Svalbard, to derive water content of the firn profiles after the 2014 and 2015 melt seasons. We do this by comparing measured and simulated rates of freezing front propagation. The calculated volumetric water content of firn is ~1.0–2.5 vol.% above the depth of 5 m and <0.5 vol.% below. Results derived using different thermistor strings suggest a prominent lateral variability in firn water content. Reported values are considerably lower than those commonly used in snow/firn models. This is interpreted as a result of preferential water flow in firn leaving dry volumes within wetted firn. This suggests that the implementation of irreducible water content values below 0.5 vol.% within snow/firn models should be considered at the initial phase of water infiltration.

中文翻译：

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斯瓦尔巴群岛 Lomonosovfonna 的冷杉含水量，来自地下温度测量

毛细作用力将水保留在孔隙中的潜力是冰川中雪和冰的一个重要特性。悬浮在孔隙中的融水对径流没有贡献，并且可能在冬季重新冻结，这会影响气候质量平衡以及地下密度和温度。然而，冷水含量的测量具有挑战性，文献中报道的数值很少。在这里，我们使用在斯瓦尔巴群岛的 Lomonosovfonna (1200 m asl) 堆积区测量的地下温度和密度来推导出 2014 年和 2015 年融化季节之后冰杉剖面的含水量。我们通过比较冰冻前沿传播的测量和模拟速率来做到这一点。计算出的冰层体积含水量在 5 m 以上深度约为 1.0-2.5 vol.%，低于 0.5 vol.%。使用不同热敏电阻串得出的结果表明，冷水含量存在显着的横向变化。报告的值远低于雪 / 冷杉模型中常用的值。这被解释为优先水流在林中的结果，在湿林中留下了干燥的体积。这表明应在水入渗的初始阶段考虑在雪/冰模型中实施低于 0.5 vol.% 的束缚水含量值。