Abstract
Abstract. We have coupled the FAMOUS global AOGCM (atmosphere-ocean general circulation model) to the Glimmer thermomechanical ice-sheet model in order to study the development of ice-sheets in north-east America (Laurentia) and north-west Europe (Fennoscandia) following glacial inception. This first use of a coupled AOGCM–ice-sheet model for a study of change on long palæoclimate timescales is made possible by the low computational cost of FAMOUS, despite its inclusion of physical parameterisations similar in complexity to higher-resolution AOGCMs. With the orbital forcing of 115 ka BP, FAMOUS–Glimmer produces ice caps on the Canadian Arctic islands, on the north-west coast of Hudson Bay and in southern Scandinavia, which grow to occupy the Keewatin region of the Canadian mainland and all of Fennoscandia over 50 ka. Their growth is eventually halted by increasing coastal ice discharge. The expansion of the ice-sheets influences the regional climate, which becomes cooler, reducing the ablation, and ice accumulates in places that initially do not have positive surface mass balance. The results suggest the possibility that the glaciation of north-east America could have begun on the Canadian Arctic islands, producing a regional climate change that caused or enhanced the growth of ice on the mainland. The increase in albedo (due to snow and ice cover) is the dominant feedback on the area of the ice-sheets and acts rapidly, whereas the feedback of topography on SMB does not become significant for several centuries, but eventually has a large effect on the thickening of the ice-sheets. These two positive feedbacks are mutually reinforcing. In addition, the change in topography perturbs the tropospheric circulation, producing some reduction of cloud, and mitigating the local cooling along the margin of the Laurentide ice-sheet. Our experiments demonstrate the importance and complexity of the interactions between ice-sheets and local climate.
Highlights
The repeated formation, advance, retreat and disappearance of extensive Northern Hemisphere (NH) ice-sheets is the defining characteristic of the glacial cycles of the Pleistocene
Because we require sufficient spatial resolution to represent the pronounced gradients of surface mass balance (SMB) in areas of mountainous topography, which are important for glacial inception, and across steep ice-sheet margins, which have a width of tens of kilometres, SMB is computed on the Glimmer grid
We have coupled the FAMOUS global atmosphere-ocean general circulation model (AOGCM) to the Glimmer thermomechanical ice-sheet model in order to simulate the coevolution of climate and ice-sheets following glacial inception in two domains: north-east America (Laurentia) and north-west Europe (Fennoscandia)
Summary
The repeated formation, advance, retreat and disappearance of extensive Northern Hemisphere (NH) ice-sheets is the defining characteristic of the glacial cycles of the Pleistocene. In the present work, which extends that of Browne (2009), we follow an approach between the second and the third: we couple an ice-sheet model interactively and frequently to a low-resolution AOGCM This runs quickly enough that multimillennial simulations are feasible, while retaining the range of interactive processes included in typical AOGCMs used for climate projection. Because this is a new model, we have chosen a limited focus in the present work, namely on the interaction, following glacial inception, of the ice-sheets developing in particular regions with the global atmosphere and surface climate. All of these mechanisms are represented in our model, to the extent permitted by the approximations of spatial resolution and physical schemes
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