Reconstruction of 30 distinct dust and loess events during the last glacial cycle: Quantification of the hemisheric, regional, and local forcing of such weather extremes during the past
Zusammenfassung der Projektergebnisse
The aim of the proposals was the reconstruction of past atmospheric circulation patterns basing on the reconstruction of aeolian dynamics recorded in maar lake sediments from the West Eifel Volcanic field (Germany). The project started with the initial question to reconstruct 30 distinct dust and loess events during the last glacial cycle from cores of the Eifel Laminated Sediment Archive (ELSA). The first major is the observation that individual dust storms cannot be unambiguously correlated between cores. Single dust storms are not supra-regional wide mass movements, but present time of high wind speed and local deflation. However, the allocation of storm layers in the lake sediments to recent regional meteorological data of supra-regional storm gusts is statistically highly significant for at least the last decades. In addition, the surprisingly good correlation between continental dust records with the Greenland ice cores leads to the suggestion that results from Eifel maar lakes correspond to a supra-regional atmospheric state by regarding longer time intervals or major storm events. Following, we have modified our principal approach and work with times of meteorological homogeneity (frequencies per 100 years) and provide (a) the variability of storm events during the whole last glacial cycle and (b) the variability of easterly wind directions for MIS-2 and MIS-3. Both results (increased variability of overall frequency of dust events and wind direction changes during MIS-3, rather stable atmospheric circulation during full glacial conditions of MIS-2) were published. The detection of easterly wind directions is basing on a study which shows the potential of µXRF geochemistry scanning of sediment cores for the quantification of the dust content within sediment cores. It could be shown that the limestone-bearing Eifel-North-South zone is the most likely source for carbonate rich aeolian dust with in the lake sediments. Once the source is known, the reconstruction of the wind direction (westerly or easterly) is possible. In a subsequent study the causes for the significant switch in the variability of changing surface wind directions between MIS-3 and MIS-2 are studied. Here, we use AGCM runs with different prescribed SST patterns to develop a synoptic interpretation of longpersisting east wind conditions (LEWIC), which is suggested to lead to an enhanced accumulation of sediment which was transported by easterly winds to the proxy site in the Eifel region. During recent times east wind is mostly influenced by a high over the Baltic Sea, resulting in easterly to north easterly air flow during LEWIC. During the glacial climate states LEWIC events are also controlled by a low south of the Iberian Peninsula, which results in a more anticyclonic air flow from south east. The occurrence of LEWIC is shifted towards late spring and summer in all glacial runs. This is attended by an increased glacial dust transport during spring in general and explains therefore the increased frequencies of east wind layers in the sediment core from the Eifel area during MIS-3.
Projektbezogene Publikationen (Auswahl)
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(2009). A continuous highresolution dust record for the reconstruction of wind systems in central Europe (Eifel, Western Germany) over the past 133 ka, Geophysical Research Letters, 36, L20712
Klemens Seelos, Frank Sirocko, and Stephan Dietrich
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(2009). A new windstorm proxy from lake sediments - a comparison of geological and meteorological data from western Germany for the period 1965-2001. J. Geophys. Res., 114, D18106
Stephan Pfahl, Frank Sirocko, Klemens Seelos, Stephan Dietrich, Andreas Walter and Heini Wernli
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(2009): Korngrößenanalyse und Sedimentgeochemie von Seesedimenten. In: Wetter, Klima, Menschheitsentwicklung, F. Sirocko (Ed.), Theiss-Verlag, Stuttgart
Stephan Dietrich und Frank Sirocko
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(2010). The reconstruction of easterly wind directions for the Eifel region (Central Europe) during the period 40.3 - 12.9 ka BP., Clim. Past, 6, 145–154
Stephan Dietrich and Klemens Seelos
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(2010). The potential of dust detection by means of µXRF scanning in Eifel maar lake sediments. E&G - Quaternary Science Journal
Stephan Dietrich & Frank Sirocko
