Influence of solar activity and environment on 10 Be in recent natural archives [Elektronisk resurs]
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Berggren, Ann-Marie, 1969- (författare)
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Aldahan, Ala (preses)
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Possnert, Göran (preses)
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Hormes, Anne (opponent)
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Uppsala universitet Teknisk-naturvetenskapliga vetenskapsområdet (utgivare)
- Publicerad: Uppsala : Acta Universitatis Upsaliensis, 2009
- Engelska 64
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Serie: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 1651-6214 ; 654
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Sammanfattning
Ämnesord
Stäng
- Understanding the link between the Sun and climate is vital in the current incidence of global climate change, and 10 Be in natural archives constitutes an excellent tracer for this purpose. As cosmic rays enter the atmosphere, cosmogenic isotopes like 10 Be and 14 C are formed. Variations in solar activity modulate the amount of incoming cosmic rays, and thereby cosmogenic isotope production. Atmospherically produced 10 Be enters natural archives such as sediments and glaciers by wet and dry deposition within about a year of production. 10 Be from natural archives therefore provides information on past solar activity, and because these archives also contain climate information, solar activity and climate can be linked. One remaining question is to what degree 10 Be in natural archives reflects production, and to what extent the local and regional environment overprints the production signal. To explore this, 10 Be was measured at annual resolution over the last 600 years in a Greenland ice core. Measurement potentials for these samples benefited from the development of a new laboratory method of co-precipitating 10 Be with niobium. To diversify geographic location and archive media type, a pioneer study of measuring 10 Be with annual resolution in varved lake sediments from Finland was conducted, with samples from the entire 20 th century. Pathways of 10 Be into lake sediments are more complex than into glacial ice, inferring that contemporary atmospheric conditions may not be recorded. Here, it is shown for the first time that tracing the 11-year solar cycle through lake sediment 10 Be variations is possible. Results also show that on an annual basis, 10 Be deposition in ice and sediment archives is affected by local environmental conditions. On a slightly longer timescale, however, diverse 10 Be records exhibit similar trends and a negative correlation with solar activity. Cyclic variability of 10 Be deposition persisted throughout past grand solar minima, when little or no sunspot activity was recorded. 10 Be levels indicate that although solar activity has been high during the 20 th century, levels are not unprecedented in the investigated 600 years. Aerosol 10 Be/ 7 Be values indicate possible influence of stratosphere-troposphere exchange on isotope abundance and the production signal.
Ämnesord
- Natural Sciences (hsv)
- Earth and Related Environmental Sciences (hsv)
- Geology (hsv)
- Naturvetenskap (hsv)
- Geovetenskap och miljövetenskap (hsv)
- Geologi (hsv)
- NATURAL SCIENCES (svep)
- Earth sciences (svep)
- Exogenous earth sciences (svep)
- Quaternary geology (svep)
- NATURVETENSKAP (svep)
- Geovetenskap (svep)
- Exogen geovetenskap (svep)
- Kvartärgeologi (svep)
Genre
- government publication (marcgt)
Indexterm och SAB-rubrik
- cosmogenic isotopes
- beryllium
- ice cores
- varved lake sediments
- accelerator mass spectrometry
- co-precipitation
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