Svalbard Ice-Mass Evolution in past and future - Climate forcing and Teleconnections (SvIMEv-CT): 4th year

气候变化是人类在21世纪面临的主要挑战之一。它的影响是多方面的，山地冰川和冰盖造成的质量损失增加，它们对海平面上升的次要贡献是最突出的。在这方面，北极冰川和冰帽特别重要，因为它们的冰量很大，而且它们的表面积很大，是气候和海洋强迫的接触面，因此也是气候变化本身的接触面。此外，北极是未来气温上升预测最高的地区。因此，北极冰块减少及其对海平面上升的贡献的重要性预计将在未来进一步增加。该项目的目的是根据RCP 2.6、RCP 4.5、RCP 6.0和RCP 8.5四种普遍考虑的未来气候情景，对未来气候物质平衡和斯瓦尔巴特群岛所有冰川和冰帽的冰块演变的时空变异性进行可靠的预测。这些情景中的每一种都将由十个不同的全球环流模型组合来表示。必要的模拟将使用在SvIMEv-CT项目的头三年期间开发和建立的空间分布的气候物质平衡模型进行。在该项目的第四年，该模型将扩展到一个耦合的“冰川-变化模型”，该模型考虑了冰川表面地形和表面范围在每年间隔上的波动。这一冰川变化模型的准确性和可靠性将以斯瓦尔巴群岛中部的两个具体冰川(Elfenbeinbreen和Sveigbreen)为例进行测试。所获得的结果将与近年来已知的冰川退缩阶段以及使用一维流线模型获得的冰川变化预测进行比较。冰川变化模型将由来自十个全球环流模型的空间分布的、统计上缩小的气温和降水数据以及模拟的净短波辐射通量来强制执行。后者解释了模拟的、空间分布的地表反照率可变性和全球环流模型得出的云量条件。该模型将在整个21世纪运行，以获得冰川质量平衡、冰川面积和体积变化的预测，以及到2100年斯瓦尔巴群岛冰块对海平面上升的相关贡献。

Climate change is one of the major challenges humanity has to face during the 21st century. Its effects are numerous with increased mass loss from mountain glaciers and ice caps and their sub-stantial contribution to sea level-rise being among the most prominent. In this context, Arctic glaci-ers and ice caps are especially important due to their extensive ice volume and due to their large surface area that acts as a contact surface to climate and oceanic forcing and thus to climate change itself. The Arctic is, moreover, the region of highest predicted future air-temperature in-creases. Therefore, the importance of losses of ice masses in the Arctic and their contribution to sea-level rise is expected to even increase in the future.The aim of the project is to achieve reliable projections of the spatial and temporal variability of future climatic mass balance and ice-mass evolution of all glaciers and ice caps of Svalbard ac-cording to the four commonly considered future climate scenarios RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5. Each of these scenarios will be represented by an ensemble of ten different global circulation models. The necessary modelling will be done using the spatially distributed climatic mass balance model developed and setup during the first three years of the SvIMEv-CT project. During the 4th year of the project, the model will be extended to a coupled "glacier-change model" that accounts for fluctuations of glacier surface topography and surface extent on annual intervals. The accuracy and reliability of this glacier-change model will be tested for the example of two specific glaciers in central Svalbard (Elfenbeinbreen and Sveigbreen). Comparison of the obtained results will be done against known glacier-retreat stages over recent years and against glacier-change projections obtained by using a 1D flow-line model. The glacier-change model will be forced by spatially distributed, statistically downscaled air temperature and precipitation data from the ten global circulation models and by modeled net shortwave radiation fluxes. The latter account for modelled, spatially distributed surface albedo variability and global circulation model-derived cloud-cover conditions. The model will be run over the entire 21st century in order to obtain projections of glacier mass balance, of glacier area and volume changes as well as of the associated sea level-rise contributions of the ice masses of Svalbard until 2100.