Annualmeeting:2017 CSDMS meeting-057

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Towards representing thermokarst processes in land surface models

Jan Nitzbon, Alfred Wegener Institute for Polar and Marine Research Potsdam , Germany.
Moritz Langer, Humboldt University of Berlin Berlin , Germany.
Sebastian Westermann, Uni Oslo Oslo , Norway.
Guido Grosse, Alfred Wegener Institute for Polar and Marine Research Potsdam , Germany.
Julia Boike, Alfred Wegener Institute for Polar and Marine Research Potsdam , Germany.

Nitzbon csdms poster A0 final.png

Large-scale Earth system and land surface models often lack an adequate representation of subgrid-scale processes in permafrost landscapes. Small-scale processes such as thermokarst formation might, however, considerably impact the energy and carbon budgets in way which is not resolved within large-scale models. Since a spatially high-resolved simulation of such processes is not feasible, novel techniques for up-scaling subgrid processes are demanded.

Within this work a one-dimensional model of the ground thermal regime of land surfaces, CryoGrid 3, is employed to conceptually represent small-scale features of permafrost landscapes, particularly those related to thermokarst. For example, the model has been shown to adequately describe the degradation of permafrost underneath waterbodies in a warming climate. Using tiling approaches such point-wise realizations can be up-scaled in a statistical way in order to represent larger land surface units. The model development is closely linked to field campaigns to the Lena River Delta in Siberia which offers very diverse land surface features such as polygonal tundra and thermos-erosional valleys. These features are related to the region’s diverse soil stratigraphies, in particular the occurrence of ice-rich ground. Combining field measurements with modelling ultimately allows an improvement in the qualitative and quantitative understanding of the typical geomorphological processes in permafrost landscapes and their representation in large-scale land surface models.