Cosmogenic Al-26 in atmospheric and climate research

One of the scientific challenges of our time is a better understanding of the climate on Earth. For example, the effect of the "variable" sun on the climate and the interplay of the various domains on Earth (atmosphere, biosphere, ocean, land) are still poorly understood. There is a clear need for more data to support our understanding of these processes, in order to predict future climate developments through reliable climate modelling. Tracing long-lived cosmogenic radionuclides through the environment has become a very powerful tool in climate research since the ultra-sensitive detection method of accelerator mass spectrometry (AMS) became available. We propose to extend the list of cosmogenic radionuclides, which are used in atmospheric and climate research (Be-10, C-14, Cl-36), by the so far little investigated Al-26 (half-life = 0.72 million years). Adding Al-26 to this group should certainly help to better understand the complex processes governing climate. In particular, it would be very interesting to use Al-26 for dating old climate archives (e.g. deep ice cores) in combination with Be-10 (half- life = 1.5 million years). However, before Al-26 can be used as a proxy, groundwork on Al-26 must be performed. This includes studying the sources and transport of Al-26 in the atmosphere, and the development of efficient processing and AMS measurements of air and ice samples. An important asset for this research proposal is the existence of the Vienna Environmental Research Accelerator (VERA), a dedicated AMS facility at the Institut für Isotopenforschung und Kernphysik, Universität Wien. VERA started operation in 1996, and has since developed into one of the most versatile AMS facilities in the world. In particular, the hitherto most sensitive Al-26/Al-27 isotope ratio measurement (~5e-16) has been performed at VERA. The VERA group will carry out this project in close collaboration with the "Ice Group" of the Institut für Umweltphysik, Universität Heidelberg. The latter will not only provide airfilters and ice samples from Antarctica and various other locations, but will also make essential contribution to the project through its long-time experience in atmospheric and climatic research. We believe that in such a multidisciplinary project, a collaboration between two groups of complementary skills is both necessary and mutually beneficial.

One of the scientific challenges of our time is a better understanding of the climate on Earth. For example, the effect of the "variable" sun on the climate and the interplay of the various domains on Earth (atmosphere, biosphere, ocean, land) are still poorly understood. There is a clear need for more data to support our understanding of these processes, in order to predict future climate developments through reliable climate modelling. Tracing long-lived cosmogenic radionuclides through the environment has become a very powerful tool in climate research since the ultra-sensitive detection method of accelerator mass spectrometry (AMS) became available. We propose to extend the list of cosmogenic radionuclides, which are used in atmospheric and climate research (Be-10, C-14, Cl-36), by the so far little investigated Al-26 (half-life = 0.72 million years). Adding Al-26 to this group should certainly help to better understand the complex processes governing climate. In particular, it would be very interesting to use Al-26 for dating old climate archives (e.g. deep ice cores) in combination with Be-10 (half- life = 1.5 million years). However, before Al-26 can be used as a proxy, groundwork on Al-26 must be performed. This includes studying the sources and transport of Al-26 in the atmosphere, and the development of efficient processing and AMS measurements of air and ice samples. An important asset for this research proposal is the existence of the Vienna Environmental Research Accelerator (VERA), a dedicated AMS facility at the Institut für Isotopenforschung und Kernphysik, Universität Wien. VERA started operation in 1996, and has since developed into one of the most versatile AMS facilities in the world. In particular, the hitherto most sensitive Al-26/Al-27 isotope ratio measurement (~5e-16) has been performed at VERA. The VERA group will carry out this project in close collaboration with the "Ice Group" of the Institut für Umweltphysik, Universität Heidelberg. The latter will not only provide airfilters and ice samples from Antarctica and various other locations, but will also make essential contribution to the project through its long-time experience in atmospheric and climatic research. We believe that in such a multidisciplinary project, a collaboration between two groups of complementary skills is both necessary and mutually beneficial.