Global Change Abstracts The Swiss Contribution - SCNAT

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166 Global Change Abstracts – The Swiss Contribution | Past Global Changes presence of sweet chestnut (Castanea sativa Mill.) in southern Switzerland. Sweet chestnut trees play a key role in Mediterranean woodlands, and for longer than two millennia have been used as a food source. Based on palynological evidence it is commonly believed that in southern Switzerland C. sativa was first introduced 2000 years ago by the Romans, who cultivated it for wood and fruit production. Our results indicate that this tree species was present on the southern slopes of the Alps similar to 1500 years earlier than previously assumed, and therefore was likely introduced independently from cultivation by the Romans. Nuclear Instruments Methods in Physics Research Section B Beam Interactions with Materials and Atoms, 2007, V259, N1, JUN, pp 398-402. 08.1-334 Cosmogenic Be-10-ages from the Store Koldewey island, NE Greenland Hakansson L, Graf A, Strasky S, Ivy Ochs S, Kubik P W, Hjort C, Schlüchter C Switzerland, Sweden, USA Paleontology , Cryology / Glaciology , Geology Earlier work in northeast Greenland has suggested a limited advance of the Greenland Ice Sheet during the Last Glacial Maximum (LGM). However, this concept has recently been challenged by marine geological studies, indicating grounded ice on the continental shelf at this time. New Be-10-ages from the Store Koldewey island, northeast Greenland, suggest that unscoured mountain plateaus at the outer coast were covered at least partly by cold-based ice during the LGM. It is, however, still inconclusive whether this ice was dynamically connected to the Greenland Ice Sheet or not. Regardless of the LGM ice sheet extent, the Be-10 results from Store Koldewey add to a growing body of evidence suggesting considerable antiquity of crystalline unscoured terrain near present and Pleistocene ice sheet margins. Geografiska Annaler Series A Physical Geography, 2007, V89A, N3, pp 195-202. 08.1-335 Evidence for recurrent changes in Lower Triassic oceanic circulation of the Tethys: The delta C-13 record from marine sections in Iran Horacek M, Richoz S, Brandner R, Krystyn L, Spoetl C Switzerland, Austria Paleontology , Geochemistry & Geophysics , Oceanography , Geology Stable carbon isotope curves derived from Lower Triassic carbonate rocks from three Iranian sections are established to investigate changes in the carbon cycle during the Early Triassic in this area. The sections are located in the south-center (Abadeh), north (Amol), and northwest (Zal) of Iran. All three curves show a similar pattern starting out with high delta C-13 values in the uppermost Permian decreasing across the Permian-Triassic boundary, an increase toward more positive values during the Griesbachian that slowly increase further up during the Dienerian, followed by a positive excursion to values as high as +8%o near the Dienerian/Smithian boundary. During the Smithian values return to below O%o, whereas second positive excursion to values higher than + 3%o is recorded at the Smithian /Spathian boundary, again followed by a drop in delta C-13 into the Spathian and a final excursion to positive values at the Spathian /Anisian boundary. The results from these Iranian sections are consistent with previous studies from Italy and China, thus strongly suggesting that the recorded delta C-13 variability represents at least Tethys-wide geochemical signals. Moreover, the new curves reveal evidence of hich-amplitude, frequent oscillations pointing toward rapid and profound changes in the global carbon cycle during the Lower Triassic. Stratification of the ocean interrupted by episodic overturning transporting deep water to the ocean surface is a viable mechanism to account for the recorded isotope variations. Provided that the delta C-13 curve is representative of the global Lower Triassic ocean. it has high potential for accurately dating sedimentary successions via chemostratigraphy. Palaeogeography Palaeoclimatology Palaeoecology, 2007, V252, N1-2, AUG 20, pp 355-369. 08.1-336 1. Flaje-Kiefern (Krusne Hory Mountains): Late Glacial and Holocene vegetation development Jankovska V, Kunes P, van der Knaap W O Czech Republic, Switzerland Paleontology , Forestry , Plant Sciences Grana, 2007, V46, N3, pp 214-216. 08.1-337 Microgram level radiocarbon (C-14) determination on carbonaceous particles in ice Jenk T M, Szidat S, Schwikowski M, Gäggeler H W, Wacker L, Synal H A, Saurer M Switzerland Cryology / Glaciology , Geochemistry & Geophysics Paleontology , Instruments & Instrumentation In climate research the interest on carbonaceous particles has increased over the last years because of their influence on the radiation balance of the earth. Nevertheless, there is a paucity of available
Global Change Abstracts – The Swiss Contribution | Past Global Changes data regarding their concentrations and sources in the past. Such data would be important for a better understanding of their effects and for estimating their influence on future climate. Here, a technique is described to extract carbonaceous particles from ice core samples with subsequent separation of the two main constituents into organic carbon (OC) and elemental carbon (EC) for analysis of their concentrations in the past. This is combined with further analysis of OC and EC C-14/C-12 ratios by accelerator mass spectrometry (AMS), what can be used for source apportionment studies of past emissions. We further present how C-14 analysis of the OC fraction could be used in the future to date any ice core extracted from a high-elevation glacier. Described sample preparation steps to final analysis include the combustion of micrograms of water- insoluble carbonaceous particles, primary collected by filtration of melted ice samples, the graphitisation of the obtained CO 2 to solid AMS target material and final AMS measurements. Possible fractionation processes were investigated for quality assurance. Procedural blanks were reproducible and resulted in carbon masses of 1.3 +/- 0.6 µ g OC and 0.3 +/- 0.1 µ g EC per filter. The determined fraction of modern carbon (f(M)) for the OC blank was 0.61 0.13. The analysis of processed IAEA-C6 and IAEA-C7 reference material resulted in f(M) = 1.521 +/- 0.011 and delta C-13 = -10.85 0.19%, and f(M) = 0.505 +/- 0.011 and delta C-13 = - 14.21 0.19 parts per thousand, respectively, in agreement with consensus values. Initial carbon contents were thereby recovered with an average yield of 93%. Nuclear Instruments Methods in Physics Research Section B Beam Interactions with Materials and Atoms, 2007, V259, N1, JUN, pp 518-525. 08.1-338 Orbital and millennial Antarctic climate variability over the past 800,000 years Jouzel J, Masson Delmotte V, Cattani O, Dreyfus G, Falourd S, Hoffmann G, Minster B, Nouet J, Barnola J M, Chappellaz J, Fischer H, Gallet J C, Johnsen S, Leuenberger M, Loulergue L, Lüthi D, Oerter H, Parrenin F, Raisbeck G, Raynaud D, Schilt A, Schwander J, Selmo E, Souchez R, Spahni R, Stauffer B, Steffensen J P, Stenni B, Stocker T F, Tison J L, Werner M, Wolff E W France, Germany, Denmark, Iceland, Switzerland, Italy, Belgium, England Paleontology , Cryology / Glaciology , Meteorology & Atmospheric Sciences A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending 167 this climate record back to marine isotope stage 20.2, similar to 800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records. Science, 2007, V317, N5839, AUG 10, pp 793-796. 08.1-339 Applying SAR-IRSL methodology for dating fine-grained sediments from lake El’gygytgyn, north-eastern Siberia Juschus O, Preusser F, Melles M, Radtke U Germany, Switzerland Geology , Geochemistry & Geophysics , Paleontology Lake El’gygytgyn is situated in a 3.6 Ma old impact crater in north- eastern Siberia and probably represents one of the most complete archives of Arctic climate change. Investigated here is the potential of infra-red stimulated luminescence (IRSL) using the single-aliquot regenerative-dose (SAR) approach for dating sediments from this lake. Independent age control is available from a published age model of a parallel core that is based on tuning sediment proxies with regional insolation and the results of previous multiple aliquot IRSL dating. Although the site is located within volcanic bedrock, anomalous fading seems to have little effect on the calculated ages. The modelled water content for the entire time of burial is seen as the most prominent uncertainty at this particular site. Despite these potential error sources, SAR-IRSL ages are in acceptable agreement with the given timeframe and clearly point to the possibility to establish independent chronologies at this site up to at least 400,000 years. Quaternary Geochronology, 2007, V2, N1-4, SI, pp 187-194. 08.1-340 Unfractionated excess air: The result of incomplete dissolution of entrapped air? Klump S, Cirpka O A, Kipfer R Switzerland Paleontology , Geochemistry & Geophysics Geochimica et Cosmochimica Acta, 2007, V71, N15, AUG, SS, p A496.
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