On the importance of rapid dynamics for the stability of the Greenland Ice Sheet

设想的项目的目标是评估今天格陵兰岛的稳定性，这与古证据一致，这些证据表明更新世间冰期延长了几乎不结冰的时期。中心重点将放在(快速)冰动力学与地表质量平衡变化的作用上，这些变化预计将控制格陵兰冰盖的冰消失率。为此，我们将结合已建立的并行冰盖模式(PISM)和区域能量-水分平衡地形模式(REMBO)。这两个模型在计算上都非常有效，可以对冰川周期进行模拟，并对广泛的模型参数和气候输入不确定性进行采样。冰盖的表面质量平衡与表面高度成正反馈，这已被证明产生了格陵兰冰盖的滞后行为。PISM和REMBO的交互耦合提供了明确模拟这一反馈和其他反馈的影响的机会，这可能会被快速的冰动力学显著加速。使用耦合模型，我们将创建过去两个冰川周期的模拟集合，然后对格陵兰冰盖进行稳定性分析。这些模拟可以根据它们模拟过去冰川消融过程的开始和持续时间的能力而受到限制，这提供了一个重要的验证方法。考虑到快速动态，我们预计拟议的项目将大大促进我们对格陵兰冰盖潜在的临界点和相关的衰退时间尺度的了解。

The target of the envisaged project is to assess the stability of present-day Greenland, consistent with paleo evidence which suggests extended, almost ice-free periods during Pleistocene interglacials. Central focus will be given to the role of (rapid) ice dynamics versus surface mass balance changes, which are expected to control the rates of ice loss from the Greenland Ice Sheet. To this end, we will couple the well-established Parallel Ice Sheet Model (PISM) and Regional Energy-Moisture Balance Orographic Model (REMBO). Both models are computationally so efficient to allow running simulations of glacial cycles and sampling a wide range of model parameters as well as climate input uncertainties. The ice-sheet’s surface mass balance is enmeshed in a positive feedback with the surface elevation which has been shown to yield hysteresis behaviour of the Greenland Ice Sheet. The interactive coupling of PISM and REMBO provides the opportunity to explicitly model the impact of this and other feedbacks, which might be significantly sped up by fast ice dynamics. With the coupled model, we will create an ensemble of simulations of the past two glacial cycles, followed by a stability analysis of the Greenland Ice Sheet. The simulations can be constrained based on their ability to simulate the onset and duration of past deglaciation processes which provides an important validation method. Accounting for rapid dynamics, we expect that the proposed project will substantially advance our understanding of potential tipping points and the associated timescales of decay for the Greenland Ice Sheet.