Glacier retreat on Kilimanjaro and associated climate change

The climatological interpretation of modern glacier recession on Kilimanjaro, East Africa, which began round 1880, has remained speculative to date. In recent reports, vanishing of these glaciers has been attributed to general global warming only, an overly simplistic view disregarding the peculiar climatic and environmental settings of the mountain. The proposed project aims at establishing the precise mechanisms of glacier-climate interaction on Kilimanjaro. For that, the particular impact of tropical climate on glaciers as well as the special environmental settings on Kilimanjaro will be considered, e.g. the modification force of the mountain`s height and size on the mid- tropospheric and local circulation, and the peculiar shape and dynamics of the glaciers. To reach the overall aim, investigations span two different scales, a microscale and a mesoscale, which solely both in combination will lead to a better understanding of the climatological causes of the observed glacier retreat. All investigations must be performed in the special contexts of (1) East African climate evolution over the past 150 years, which is indicated reliably by several climatic proxy data pointing to a major drop in air humidity around 1880, and of (2) the regional circulation`s large-scale linkages. For the microscale, it is decisive to examine several separate glacier regimes that differ in mechanisms of energy and mass exchange at the glacier-atmosphere interface, and the climatic controls behind them. Micrometeorological measurements will be carried out on the mountain in order to obtain input data for the microscale models. Parallel to the microscale investigations, a regional atmospheric modeling system (RAMS) will be used to simulate the mesoscale circulation over the mountain, covering the area between East Africa and the western Indian Ocean, Kilimanjaro`s source region of moisture. Simulations with RAMS are supported by data from existing General Circulation Model (GCM) runs, in order to establish boundary conditions for mesoscale sensitivity studies. As the knowledge on the climatic controls of glacier ablation enhances from the microscale investigations, the RAMS will finally be run to simulate the climatic differences between times of present glacier recession and preceding glacier growth. With that last step, information on climate variability and climate change will emerge for this part of the tropics. Since the tropical circulation systems exerts a great influence on the global climate, the project should moreover provide valuable findings that can be considered in global climate models trying to predict the future climate of our earth.

The climatological interpretation of modern glacier recession on Kilimanjaro, East Africa, which began round 1880, has remained speculative to date. In recent reports, vanishing of these glaciers has been attributed to general global warming only, an overly simplistic view disregarding the peculiar climatic and environmental settings of the mountain. The proposed project aims at establishing the precise mechanisms of glacier-climate interaction on Kilimanjaro. For that, the particular impact of tropical climate on glaciers as well as the special environmental settings on Kilimanjaro will be considered, e.g. the modification force of the mountain`s height and size on the mid- tropospheric and local circulation, and the peculiar shape and dynamics of the glaciers. To reach the overall aim, investigations span two different scales, a microscale and a mesoscale, which solely both in combination will lead to a better understanding of the climatological causes of the observed glacier retreat. All investigations must be performed in the special contexts of (1) East African climate evolution over the past 150 years, which is indicated reliably by several climatic proxy data pointing to a major drop in air humidity around 1880, and of (2) the regional circulation`s large-scale linkages. For the microscale, it is decisive to examine several separate glacier regimes that differ in mechanisms of energy and mass exchange at the glacier-atmosphere interface, and the climatic controls behind them. Micrometeorological measurements will be carried out on the mountain in order to obtain input data for the microscale models. Parallel to the microscale investigations, a regional atmospheric modeling system (RAMS) will be used to simulate the mesoscale circulation over the mountain, covering the area between East Africa and the western Indian Ocean, Kilimanjaro`s source region of moisture. Simulations with RAMS are supported by data from existing General Circulation Model (GCM) runs, in order to establish boundary conditions for mesoscale sensitivity studies. As the knowledge on the climatic controls of glacier ablation enhances from the microscale investigations, the RAMS will finally be run to simulate the climatic differences between times of present glacier recession and preceding glacier growth. With that last step, information on climate variability and climate change will emerge for this part of the tropics. Since the tropical circulation systems exerts a great influence on the global climate, the project should moreover provide valuable findings that can be considered in global climate models trying to predict the future climate of our earth.