Tephra influence on glacier ablation in Iceland since 2010 (TIOGA-Ice2010+)

冰上粒子以其对冰川能量和质量平衡的影响而闻名。沉积在冰川上的薄层气溶胶降低了反照率，增加了吸收的总辐射并增强了消融，而厚层气溶胶往往具有绝缘作用。颗粒覆盖物的粒度和化学成分在决定这些影响的强度方面起着重要作用。大规模的非绝缘颗粒覆盖物可能来自大气中的黑碳（ABC）沉积或火山灰的沉降物。细粒和薄层ABC的沉积面积较大，在区域尺度上表现出相当均匀的格局。火山灰也可能在区域尺度上沉积，但其厚度具有很高的空间变异性。火山灰的非均匀分布使冰川广泛影响的评估复杂化。因此，到目前为止，大多数相关研究都集中在ABC沉积的影响上。相比之下，虽然世界上许多地区的活火山活动和大面积的冰川覆盖地区同时发生，但对火山灰沉降的影响却几乎没有进行过研究。在2010年和2011年，Eyjafjalljökull和Grímsvötn火山的两次大爆发将火山灰扩散到冰岛冰盖的大部分地区。由于这些地区相当容易进入，而且相关数据也很容易获得，因此它们为研究火山火山泥沉积对冰川物质平衡的影响提供了理想的机会。拟议项目的目的是开发一种空间分布方法，用于模拟冰川上冰冰沉积物对冰川质量平衡的影响，从而能够在区域尺度上处理这些沉积物在厚度和化学成分方面的时空不均匀性。该模型将应用于最近的两次冰岛火山爆发以及引起的Vatnajökull、Myrdalsjökull和Eyjafjallajökull冰盖质量平衡的变化。该方法不仅依赖于火舌厚度的时不变数据，而且还将考虑该量的时间变异性。通过这种方式，该项目将提供一个连续的传递函数链，作为解释物，在内部，由粒度分布和沉积冰的化学成分构成的微观强迫和由气象条件构成的外部强迫之间，以及由此导致的冰川消融和物质平衡的宏观变化。除了弥补在这方面关于冰-火山相互作用的科学知识方面的差距之外，该项目还将创造一个潜在的宝贵工具，用于减轻冰川地区火山爆发后的危害。建模方法有助于快速量化火山爆发后后续河流系统的消融和径流变化。这对于保护受影响地区的基础设施和住区可能很重要。

Supraglacial particles are known for their impact on glacier energy and mass balance. Thin layers of aerosols deposited on the glacier reduce the albedo, increase absorbed global radiation and enhance ablation whereas thick layers tend to have insulating effects. Grain size and chemical composition of the particle cover play an important role in determining the intensity of these influences. Large scale, non-insulating particle covers may originate from either atmospheric black carbon (ABC) deposition or fallout of volcanic ashes. Deposition of fine-grained and thin layers of ABC extends over large areas showing a rather uniform pattern on the regional scale. Volcanic ashes may also be deposited over regional-scale areas but show a high spatial variability of thicknesses. The heterogeneous dispersal of volcanic ashes complicates glacier wide influence assessments. Hence and so far, most related studies focused on the influence of ABC deposition. The influences of volcanic ash fall, in contrast, have hardly been studied, even though active volcanism and extensive glacierized areas coincide in various regions of the world. In 2010 and 2011 two major eruptions of Eyjafjalljökull and Grímsvötn volcanos spread tephra over large parts of the Icelandic ice caps. Due to the rather easy accessibility of these areas and the availability of related data they represent an ideal opportunity for a study of the influences of volcanic tephra deposits on glacier mass balance.The aim of the proposed project is to develop a spatially distributed approach for modeling of the influences of supraglacial tephra deposits on glacier mass balance that is able to cope with the spatiotemporal inhomogeneities of these deposits regarding thickness and chemical composition on a regional scale. The model will be applied to the two recent Icelandic eruptions and the induced changes in mass balance of Vatnajökull, Myrdalsjökull and Eyjafjallajökull ice caps. The approach will not only rely on time invariant data of tephra thickness but will also account for the temporal variability of this quantity. By this means, the project will provide a continuous chain of transfer functions between, as explicants, the interior, micro-scale forcing by grain-size distribution and chemical composition of deposited tephra and the exterior forcing by meteorological conditions and, as resultant, the macro-scale changes in glacier ablation and mass balance. Besides the closing of the gap in scientific knowledge regarding ice-volcano interactions in this respect, the project will also create a potentially valuable tool for the purpose of hazard mitigation after volcanic eruptions in glacierized regions. The modeling approach facilitates a fast quantification of changes in ablation and runoff in subsequent river systems after volcanic eruptions. This might be important for the protection of infrastructure and settlements in affected regions.