With a unique biogeophysical signature relative to other freshwater sources, meltwater from glaciers plays a crucial role in the hydrological and ecological regime of high latitude coastal areas. Today, as glaciers worldwide exhibit persistent negative mass balance, glacier runoff is changing in both magnitude and timing, with potential downstream impacts on infrastructure, ecosystems, and ecosystem resources. However, runoff trends may be difficult to detect in coastal systems with large precipitation variability. Here, we use the coupled energy balance and water routing model SnowModel-HydroFlow to examine changes in timing and magnitude of runoff from the western Juneau Icefield in Southeast Alaska between 1980 and 2016. We find that under sustained glacier mass loss (−0.57 ± 0.12 m w. e. a⁻¹), several hydrological variables related to runoff show increasing trends. This includes annual and spring glacier ice melt volumes (+10% and +16% decade⁻¹) which, because of higher proportions of precipitation, translate to smaller increases in glacier runoff (+3% and +7% decade⁻¹) and total watershed runoff (+1.4% and +3% decade⁻¹). These results suggest that the western Juneau Icefield watersheds are still in an increasing glacier runoff period prior to reaching “peak water.” In terms of timing, we find that maximum glacier ice melt is occurring earlier (2.5 days decade⁻¹), indicating a change in the source and quality of freshwater being delivered downstream in the early summer. Our findings highlight that even in maritime climates with large precipitation variability, high latitude coastal watersheds are experiencing hydrological regime change driven by ongoing glacier mass loss.

中文翻译：

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不断变化的水文状况：高纬度沿海流域冰川融冰和冰川径流的大小和时间趋势

与其他淡水资源相比，冰川融水具有独特的生物地球物理特征，在高纬度沿海地区的水文和生态状况中起着至关重要的作用。今天，随着全球冰川呈现持续的负质量平衡，冰川径流的规模和时间都在发生变化，对基础设施、生态系统和生态系统资源有潜在的下游影响。然而，在具有大降水变率的沿海系统中，径流趋势可能难以检测。在这里，我们使用耦合能量平衡和水路由模型 SnowModel-HydroFlow 来检查 1980 年至 2016 年阿拉斯加东南部朱诺冰原西部径流时间和大小的变化。我们发现，在持续冰川质量损失（-0.57 ± 0.12 m 我们 a ^-1)，几个与径流相关的水文变量显示出增加的趋势。这包括每年和春季冰川融冰量（+10% 和 +16% 十年^-1），由于降水比例较高，冰川径流增加较小（+3% 和 +7% 十年^-1）和总流域径流（+1.4% 和 +3% 十年^-1）。这些结果表明，在达到“峰值水量”之前，朱诺西部冰原流域仍处于冰川径流不断增加的时期。在时间方面，我们发现最大冰川融冰发生得更早（2.5 天十年^-1)，表明初夏向下游输送的淡水的来源和质量发生了变化。我们的研究结果强调，即使在降水变化很大的海洋气候中，高纬度沿海流域也正在经历由持续冰川质量损失驱动的水文状况变化。