Global Change Abstracts The Swiss Contribution - SCNAT

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174 Global Change Abstracts – The Swiss Contribution | Past Global Changes central role, especially in the later stages of OAE 2. Phosphorus and TOC accumulation patterns in the Bonarelli Level in both Furlo and Manilva suggest a similar process although other factors may also be involved. (c) 2007 Elsevier Ltd. All rights reserved. Cretaceous Research, 2007, V28, N4, AUG, pp 597-612. 08.1-358 Glacial in situ survival in the Western Alps and polytopic autopolyploidy in Biscutella laevigata L. (Brassicaceae) Parisod C, Besnard G Switzerland Cryology / Glaciology , Plant Sciences , Paleontology , Microbiology Past climatic changes and especially the ice ages have had a great impact on both the distribution and the genetic composition of plant populations, but whether they promoted speciation is still controversial. The autopolyploid complex Biscutella laevigata is a classical example of polyploidy linked to glaciations and is an interesting model to explore migration and speciation driven by climate changes in a complex alpine landscape. Diploid taxa survived the last glacial maximum in several never-glaciated areas and autotetraploids are clearly dominant in the central parts of the Alps; however, previous range-wide studies failed to identify their diploid ancestor(s). This study highlights the phylogeographical relationships of maternal lineages in the Western Alps and investigates the polyploidy process using plastid DNA sequences (trn StrnG and trnK-intron) combined with plastid DNA length polymorphism markers, which were transferable among Brassicaceae species. Twenty- one distinct plastid DNA haplotypes were distinguished in 67 populations densely sampled in the Western Alps and main lineages were identified by a median-joining network. The external Alps harboured high levels of genetic diversity, while the Central Alps contained only a subset of haplotypes due to postglacial recolonization. Several haplotypes were restricted to local peripheral refugia and evidence of in situ survival in central nunataks was detected by the presence of highly differentiated haplotypes swamped by frequent ones. As hierarchical genetic structure pointed to an independent evolution of the species in different biogeographical districts, and since tetraploids displayed haplotypes belonging to different lineages restricted to either the northern or the southern parts of the Alpine chain, polytopic autopolyploidy was also apparent in the Western Alps. Molecular Ecology, 2007, V16, N13, JUL, pp 2755-2767. 08.1-359 The EDC3 chronology for the EPICA dome C ice core Parrenin F, Barnola J M, Beer J, Blunier T, Castellano E, Chappellaz J, Dreyfus G, Fischer H, Fujita S, Jouzel J, Kawamura K, Lemieux Dudon B, Loulergue L, Masson Delmotte V, Narcisi B, Petit J R, Raisbeck G, Raynaud D, Ruth U, Schwander J, Severi M, Spahni R, Steffensen J P, Svensson A, Udisti R, Waelbroeck C, Wolff E France, Switzerland, Italy, Germany, Japan, Denmark, England Paleontology , Meteorology & Atmospheric Sciences , Cryology / Glaciology The EPICA (European Project for Ice Coring in Antarctica) Dome C drilling in East Antarctica has now been completed to a depth of 3260 m, at only a few meters above bedrock. Here we present the new EDC3 chronology, which is based on the use of 1) a snow accumulation and mechanical flow model, and 2) a set of independent age markers along the core. These are obtained by pattern matching of recorded parameters to either absolutely dated paleoclimatic records, or to insolation variations. We show that this new time scale is in excellent agreement with the Dome Fuji and Vostok ice core time scales back to 100 kyr within 1 kyr. Discrepancies larger than 3 kyr arise during MIS 5.4, 5.5 and 6, which points to anomalies in either snow accumulation or mechanical flow during these time periods. We estimate that EDC3 gives accurate event durations within 20% (2 sigma) back to MIS11 and accurate absolute ages with a maximum uncertainty of 6 kyr back to 800 kyr. Climate of the Past, 2007, V3, N3, pp 485-497. 08.1-360 Palaeoceanographic and palaeoclimatic reorganization around the Middle-Late Jurassic transition Rais P, Louis Schmid B, Bernasconi S M, Weissert H Switzerland Paleontology , Oceanography , Geology A Middle to Upper Jurassic succession of submarine hardgrounds overlain by nodular limestones is exposed in the Jura mountains and in the Helvetic of the Swiss Alps. These sediments were accumulated along the northern shelf of the cast-west trending Tethys seaway. Submarine hardgrounds and nodular limestones were also formed on the Brianconnais High, today outcropping in the middle Perminic nappe pile of the Alps. Hardgrounds record strong and persistent current activity along the northern Tethys shelf and on the Brianconnais High during the Callovian and Early Oxfordian. The transition from
Global Change Abstracts – The Swiss Contribution | Past Global Changes hardgrounds to nodular limestones corresponds to a major reorganization of Tethys oceanography. The change occurred in Plicatilis ammonite Zone (Middle Oxfordian). Carbon isotope stratigraphy, calibrated against an ammonite-dated reference section in the French Subalpine Basin, serves as a correlation tool between ammonite-dated sections and successions with poor biostratigraphic resolution. Correlation demonstrates that the end of hardground formation was synchronous over wide parts of the northern Tethys. The change in shelf sedimentation coincides with a positive carbon isotope excursion with an amplitude of 1.5%o. The change in Cisotope stratigraphy indicates that observed reorganization of current patterns along the northern Tethys shelf was coupled with global change in oceanography and climate. We propose that the change in northern Tethys sedimentation was caused by opening of new seaways at a time of progressive collapse of Pangaea. (c) 2007 Elsevier B.V. All rights reserved. Palaeogeography Palaeoclimatology Palaeoecology, 2007, V251, N3-4, AUG 8, pp 527-546. 08.1-361 Direct north-south synchronization of abrupt climate change record in ice cores using Beryllium 10 Raisbeck G M, Yiou F, Jouzel J, Stocker T F France, Switzerland Paleontology , Meteorology & Atmospheric Sciences , Cryology / Glaciology A new, decadally resolved record of the Be-10 peak at 41 kyr from the EPICA Dome C ice core (Antarctica) is used to match it with the same peak in the GRIP ice core (Greenland). This permits a direct synchronisation of the climatic variations around this time period, independent of uncertainties related to the ice age-gas age difference in ice cores. Dansgaard-Oeschger event 10 is in the period of best synchronisation and is found to be coeval with an Antarctic temperature maximum. Simulations using a thermal bipolar seesaw model agree reasonably well with the observed relative climate chronology in these two cores. They also reproduce three Antarctic warming events observed between A1 and A2. Climate of the Past, 2007, V3, N3, pp 541-547. 175 08.1-362 Temporal stability of climate-isotope relationships in tree rings of oak and pine (Ticino, Switzerland) Reynolds Henne C E, Siegwolf R T W, Treydte K S, Esper J, Henne S, Saurer M Switzerland Paleontology , Plant Sciences , Forestry Climate reconstructions based on stable isotopes in tree rings commonly rely on the assumption that climate-isotope relations are stable over time. However, studies of tree ring growth have revealed trends thought to result from either physiological changes or changes in the climate-growth relationship. We investigated whether or not similar trends exist for tree ring stable isotopic ratios using a statistical approach. Correlations between climate (temperature and precipitation amount) and tree ring cellulose delta C-13 and delta O-18 of oak and pine from Ticino, Switzerland, were calculated for the period AD 1660 - 2000. Climate calibration of tree rings was enabled by long-term monthly resolved temperature and precipitation data sets on the basis of instrumental and documentary proxy data. Overall, five findings have been identified: (1) Isotopic ratios in tree rings most strongly reflect conditions of the current growing season, (2) temporally stable climate signals are found in pine delta C-13 only, (3) all other correlations between tree ring isotopes and climate are temporally unstable and characterized by shifts in correlation sign and strength, (4) climate signals in oak are strongest in the 20th century, and (5) tree ring delta C-13 reflects local climatic conditions while delta O-18 is influenced by large- scale synoptic circulation. The nonstationary relationships observed could reflect changes in the relationship between the climate variables or a physiological adaptation to warmer conditions. Our results provide a cautionary note for the calibration of long tree ring series with 20th century relationships, at least for trees located at ecologically nonextreme sites. Global Biogeochemical Cycles, 2007, V21, N4, NOV 2 ARTN: GB4009. 08.1-363 Climatic cycles during a Neoproterozoic “snowball” glacial epoch Rieu R, Allen P A, Ploetze M, Pettke T Spain, England, Switzerland Meteorology & Atmospheric Sciences , Cryology / Glaciology , Modelling , Paleontology The profound glaciations of the Neoproterozoic Cryogenian period (ca. 850-544 Ma) represent an extreme climatic mode when, it is claimed, Earth
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