Periodic Reporting for period 4 - CoupledIceClim (Coupled climate and Greenland ice sheet evolution:past, present and future)
Periodo di rendicontazione: 2020-12-01 al 2022-05-31
This work is relevant for projections of future sea level rise as well as polar and midlatitude climate, the latter due to the closeness of Greenland to sites of deep convection.
The overall objectives of the project are to contribute to advance understanding of ice sheet and climate interactions, to improve climate and ice sheet modelling, to contribute to model intercomparison projects, and to provide projections of future ice sheet evolution accounting for major feedbacks that contribute to the timing, rate and reversibility of deglaciation at century and multi-century time scales. Examples of such feedbacks and key interactions are albedo-melt feedback, elevation-melt feedback or ocean-ice-climate interaction.
From the application of the model to future Greenland ice sheet deglaciation we provided insights into the future evolution of the energy sources for surface melt, the refreezing capacity of the ice sheet, and the contributions of different ice sheet regions to the overall mass loss. We found that the southern half of the ice sheet rapidly contributes to sea level rise under anthropogenic greenhouse warming, due to its relatively warm summer climate. However, the northern margins are very sensitive to the warming at a later stage, once a critical level of overall warming is reached. We found that thermal radiation from the atmosphere is the primary contributor to melt at early stages of mass loss, however solar radiation becomes the primary contributor at later stages, due to large activation of the positive melt-albedo feedback. At a multicentury time-scale and under high greenhouse warming, the Greenland ice sheet transitions from marine margin with iceberg calving at the fjords to a terrestrial margin. The region that transitions the last is the southwest, in connection with large snowfall accumulation there from the North Atlantic weather systems.
The coupled model has shown the great potential for further research on climate and ice sheet interaction as it connects under the same umbrella the simulation of atmospheric, ocean and ice sheet surface and dynamical changes. This common frame permits to evaluate the impacts of specific changes in the climate system on Greenland ice sheet change, and viceversa, as well as the role of feedbacks in accelerating o decelerating ice shet mass loss.
For the target of including an interactive Greenland ice sheet component in CESM, we contributed to tuning and evaluation of the ice sheet component, surface mass balance and near-surface climate simulation, downscaling between climate and ice sheet grids, and initialization procedure. We have also adapted the model to the simulation of the paleo ice sheets of the Last Glacial Maximum (21,000 years ago).
The core of these developments have been publicly released. In addition, the project has provided a set of publications on model description, evaluation and application to understanding of processes of ice-climate interactions under a warming climate. These publications have been made publicly accessible.
This is the only contribution of advanced Earth System Modelling to Greenland ice sheet projections in the last IPCC report AR6.
Progress achieved with this project is already contributing to further advancement of coupled ice sheet and climate simulation in various research groups within Europe.
The project has pioneered coupled ice sheet and climate modelling within the Ice Sheet Model Intercomparison Project 6 (ISMIP6)