Assessment of the ocean contribution to mass loss of Greenland’s peripheral glaciers – a scale-transitioning approach

除了大型的主冰盖外，格陵兰岛还拥有大量规模小得多的外围冰川。它们对格陵兰岛整体质量变化的贡献远远超过了它们在冰质量和表面积中的份额。由于它们大多位于岛屿海岸沿着的山区，这些冰块的数值模型需要考虑足够的空间分辨率，这是冰盖模型无法实现的。潮汐冰川对整体质量损失的贡献特别大。在2003年至2008年期间，外围冰川对格陵兰岛整体冰量损失的贡献为14%。它们对海平面上升的贡献预计将在未来增加，目前可用的预测表明，在RCP 8.5强迫下，21世纪外围冰川的冰量损失高达50%。周边冰川质量变化存在很强的空间变化，这反映了大气和海洋强迫机制的复杂组合。然而，目前可用的模型，能够计算区域尺度的冰川质量变化明确包括海洋强迫的锋面消融过程中的海洋终止前的冰川。除了两个模型，没有一个甚至考虑任何正面消融过程。因此，没有过去，现在或未来的估计，在格陵兰岛的周边冰川锋面消融到目前为止，该项目的目的是产生预测的未来演变格陵兰岛的周边冰川在21世纪世纪，迫使CMIP 6合奏，特别是注意到冰川。我们将量化它们的淡水排放和对海平面上升的贡献。我们将扩展开放全球冰川模型（OGGM），在其锋面消融模块中包括海洋强迫。这将得到大气和海洋边界条件专用降尺度程序的协助。我们将评估OGGM的性能方面的应用不同尺度的强迫数据，以确定是否，以及在何种程度上，优化的规模从大的天气尺度过渡到较小的本地规模的外围冰川是能够提高模型的性能。该项目的成果将使人们更好地了解海洋和大气对格陵兰周边冰川演变的影响。我们将进一步提供有关区域尺度冰川建模，特别是冰川的建模策略的最佳复杂性的建议。

Apart from the large main ice sheet, Greenland is home to a huge number of far smaller peripheral glaciers. Their contribution to the overall mass change of Greenland is greatly exceeding their share of ice mass, and surface area. Since they are mostly located in mountainous terrain along the coast of the island, numerical models of these ice masses need to consider the adequate spatial resolution, which cannot be achieved by ice sheet models. Tidewater glaciers are contributing a particularly large part to the overall mass loss. During 2003 to 2008, the peripheral glaciers contributed 14% to the overall ice mass loss of Greenland. Their contribution to sea level rise is projected to increase in the future, with currently available projections suggesting ice mass losses of the peripheral glaciers of up to 50% during the 21st century under RCP 8.5 forcing. There is strong spatial variation in peripheral glacier mass change, which mirrors a complex combination of forcing mechanisms from both atmosphere and ocean. Nevertheless, none of the currently available models which are capable of calculating regional-scale glacier mass change explicitly includes ocean forcing of frontal ablation processes at the marine-terminating fronts of tidewater glaciers. Except for two models, none even considers any frontal ablation processes at all. Hence, no past, present or future estimates of frontal ablation at Greenland's peripheral tidewater glaciers are available so far.The aim of the project is to produce projections of the future evolution of Greenland's peripheral glaciers during the 21st century, forced by the CMIP6 ensemble, with special attention to tidewater glaciers. We will quantify their freshwater discharge and contribution to sea-level rise. We will extend the Open Global Glacier Model (OGGM) to include ocean forcing in its frontal ablation module. This will be assisted by dedicated downscaling routines for both atmospheric and oceanic boundary conditions. We will evaluate the performance of OGGM with respect to the application of different scales of forcing data to determine if, and to which extent, optimized scale transitioning from the large synoptic scale down to the smaller local scale of the peripheral glaciers is able to increase model performance. The project results will provide an increased understanding of the influence ocean and atmosphere on the evolution of Greenland's peripheral glaciers. We will further provide advice regarding the optimal complexity of modeling strategies regarding regional-scale glacier modeling, particularly of tidewater glaciers.