Glacier mass-balance observations at seasonal resolution have been performed since 1914 at two sites on Claridenfirn, Switzerland. The measurements are the longest uninterrupted records of glacier mass balance worldwide. Here, we provide a complete re-analysis of the 106-year series (1914–2020), focusing on both point and glacier-wide mass balance. The approaches to evaluate and homogenize the direct observations are described in detail. Based on conservative assumptions, average uncertainties of $\pm$ 0.25 m w.e. are estimated for glacier-wide mass balances at the annual scale. It is demonstrated that long-term variations in mass balance are clearly driven by melting, whereas decadal changes in accumulation are uncorrelated with mass balance and can only be relevant in short periods. Mass change of Claridenfirn is impacted by dry calving at a frontal ice cliff. Considerations of ice volume flux at a cross-profile reveal long-term variations in frontal ice loss accounting for $\sim$ 9% of total annual ablation on average. The effect of changes in frontal ablation mostly explains $\lt$ 10% of the mass-balance difference relative to the period 1960–1990, but accounts for $\sim$ 20% in 2010–2020. Glacier mass changes are discussed in the context of observations throughout the European Alps indicating that Claridenfirn is regionally representative.

中文翻译：

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一个多世纪以来对瑞士克拉登芬的直接冰川质量平衡观测

自 1914 年以来，在瑞士克拉登菲尔的两个地点进行了季节性分辨率的冰川质量平衡观测。这些测量是全球冰川质量平衡最长的不间断记录。在这里，我们提供了对 106 年系列（1914-2020）的完整重新分析，重点关注点和冰川范围的质量平衡。详细描述了评估和均匀化直接观察的方法。基于保守假设，平均不确定性 $\pm$ 我们估计每年冰川范围的质量平衡为 0.25 m。研究表明，物质平衡的长期变化显然是由融化驱动的，而积累的年代际变化与物质平衡无关，只能在短期内相关。Claridenfirn 的质量变化受到正面冰崖干产犊的影响。跨剖面冰量通量的考虑揭示了锋面冰损失的长期变化 $\sim$ 平均每年消融总量的 9%。额叶消融变化的影响主要解释了 $\lt$ 相对于 1960-1990 年期间的质量平衡差异的 10%，但占 $\sim$ 2010-2020 年为 20%。冰川质量变化是在整个欧洲阿尔卑斯山的观测背景下讨论的，表明克拉登芬具有区域代表性。