Near surface atmospheric flow over high latitude glaciers

Abstract: In this thesis various descriptions of the near surface atmospheric flow over a high latitude glacier is used in an effort to increase our understanding of the basic flow dynamics there.Through their contribution to sea-level change, mountain glaciers play a significant role in Earth’s climate system. Properties of the near surface atmospheric flow are important for understanding glacier response to climate change.Here, the near surface atmospheric flow is studied from several perspectives including the effects of both rotation and slope. Rotation is an important aspect of most atmospheric flows and its significance for mesoscale flows have gained recognition over the last years. Similarly, the very stable boundary layer (VSBL) has lately gained interest. Within a VSBL over sloping terrain katabatic flow is known to be usual and persistent. For the present thesis a combination of numerical and simple analytical models as well as observations from the Vatnajökull glacier on Iceland have been used. The models have continuously been compared to available observations. Three different approaches have been used: linear wave modeling, analytic modeling of katabatic flow and of the Ekman layer, and numerical simulations of the katabatic flow using a state of the art mesoscale model. The analytic models for the katabatic flow and the Ekman layer used in this thesis both utilizes the WKB method to allow the eddy diffusivity to vary with height. This considerably improves the results of the models. Among other findings it is concluded that: a large part of the flow can be explained by linear theory, that good results can be obtained for surface energy flux using simple models, and that the very simple analytic models for the katabatic flow and the Ekman layer can perform adequately if the restraint of constant eddy diffusivity is relieved.