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

冰川上的颗粒以其对冰川能量和物质平衡的影响而闻名。沉积在冰川上的薄层气溶胶减少了辐射，增加了吸收的全球辐射，并增强了消融，而厚层则往往具有绝缘作用。颗粒覆盖物的粒度和化学成分在确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层可能来自大气中的黑碳（ABC）沉积或火山灰的沉降。ABC的细粒和薄层沉积在大面积上延伸，在区域范围内显示出相当均匀的模式。火山灰也可能沉积在区域规模的地区，但显示出高度的空间变化的厚度。火山灰的不均匀散布使冰川广泛影响评估复杂化。迄今为止，大多数相关研究都集中在ABC沉积的影响上。相比之下，火山灰降落的影响几乎没有得到研究，尽管世界各地都有活跃的火山活动和广泛的冰川化地区。在2010年和2011年，埃亚菲亚德火山和格里姆火山的两次大规模喷发将火山灰散布在冰岛大部分的冰盖上。由于这些地区很容易进入，而且可以获得相关数据，因此它们是研究火山碎屑沉积物对冰川物质平衡影响的理想机会。拟议项目的目的是开发一种空间分布的方法，用于模拟冰上火山碎屑沉积物对冰川物质平衡的影响，该方法能够科普这些沉积物在时空上的不均匀性，在区域范围内的厚度和化学成分。该模型将应用于冰岛最近的两次喷发以及由此引起的瓦特纳冰盖、米达尔斯冰盖和埃亚菲亚德拉冰盖质量平衡的变化。该方法将不仅依赖于火山灰厚度的时不变数据，但也将占这个数量的时间变化。通过这种方法，该项目将提供一个连续的链之间的转换函数，作为显式，内部，微观尺度强迫的粒度分布和化学成分的沉积火山灰和外部强迫的气象条件，并作为结果，宏观尺度的变化，冰川消融和质量平衡。除了填补这方面冰-火山相互作用科学知识方面的差距外，该项目还将为冰川化地区火山爆发后减轻灾害创造一个潜在的宝贵工具。该建模方法有助于快速量化火山爆发后随后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.