GIS-TIP

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.