Global Change Abstracts The Swiss Contribution - SCNAT

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180 Global Change Abstracts – The Swiss Contribution | Past Global Changes 08.1-374 Interactions between climate and vegetation during the Lateglacial period as recorded by lake and mire sediment archives in Northern Italy and Southern Switzerland Vescovi E, Ravazzi C, Arpenti E, Finsinger W, Pini R, Valsecchi V, Wick L, Ammann B, Tinner W Switzerland, Italy, Netherlands Cryology / Glaciology , Geology , Paleontology , History We reconstruct the vegetational history of the southern side of the Alps at 18,000-10,000 cal yr BP using previous and new ANIS-dated stratigraphic records of pollen, stomata, and macrofossils. To address potential effects of climatic change on vegetation, we compare our results with independent paleoclimatic series (e.g. isotope and chironomid records from the Alps and the Alpine forelands). The period before 16,000 cal yr BP is documented only at the lowland sites. The previous studies used for comparison with our new Palughetto record, however, shows that Alpine deglaciation must have started before 18,000-17,500 cal yr BP south of the Alps and that deglaciated sites were colonized by open woods and shrublands (Juniperits, tree Betula, Larix, Pinus cembra) at ca 17,500 cal yr BP. The vegetational history of a new site (Palughetto, 1040 m a.s.l.) is consistent with that of previous investigations in the study region. Our results show three conspicuous vegetational shifts delimited by statistically significant pollen zones, at ca 14,800-14,400, 13,300-12,800 and 11,600-11,200 cal yr BP. At sites situated above 1000 m a.s.l. (e.g. Palughetto, Pian di Gembro) forests expanded in alpine environments at ca 14,500 cal yr BP (onset of Bolling period, GI-1 in the Greenland ice record). At the same time, rather closed treeline communities of the lowlands were replaced by dense stands of Pinus sylvestris and Betula. These early forests and shrublands consisted of Larix, P. cembra, Juniperus, P. sylvestris, Pinus mugo, and Betula, and had become established at ca 16,000 cal yr BP, probably in response to a temperature increase. If combined with other records from the Southern Alps, our data suggest that treeline ascended by ca 800-1000 m in a few centuries at most, probably as a consequence of climatic warming at the beginning of the Bolling period. At 13,100-12,800 cal yr BP the onset of a long- lasting decline of P. sylvestris was accompanied by the expansion of Quercus and other thermophilous tree taxa below ca 600 m a.s.l. This vegetational change was probably induced by a shift to warmer climatic conditions before the onset of the Younger Dryas, as indicated by independent paleoclimatic records. Only a few centuries later, at ca 12,700-12,500calyr BP, an expansion of herbaceous taxa occurred in the lowlands as well as at higher altitudes, documenting an opening of forested habitats. This change coincided with the beginning of the Younger Dryas cooling (GS-1), which according to the paleoclimatic series (e.g. oxygen isotope series), started at 12,700-12,600 cal yr BP and lasted for about 1000 years. Environments south of the Alps responded markedly to climatic warming at the onset of the Holocene (11,600-11,500 cal yr BP). Thermophilous trees that had declined during the Younger Dryas re-expanded very rapidly in the lowlands and reached the high altitude sites below ca 1500 m a.s.l. within a few centuries at most. Our study implies that the synchronous vegetational changes observed over wide areas were probably a consequence of abrupt climatic shifts at the end of the Last Glacial Maximum (LGM) and during the Lateglacial. We emphasize that important vegetational changes such as the expansion of forests occurred millennia before the onset of similar processes in northwestern and central Europe. Quaternary Science Reviews, 2007, V26, N11-12, JUN, pp 1650-1669. 08.1-375 Primary carbonates and Ca-chloride brines as monitors of a paleo- hydrological regime in the Dead Sea basin Waldmann N, Starinsky A, Stein M Israel, Switzerland Paleontology , Geology , Meteorology & Atmospheric Sciences Lakes Samra, Lisan and the Dead Sea occupied the Dead Sea basin during the Last Interglacial (similar to 140-75ka BP), last glacial (similar to 70-14 ka BP) and Holocene periods, respectively. The age of Lake Lisan and Samra was determined by U-Th dating of primary aragonites comprising parts of the lacustrine sedimentary sequences. The lakes have periodically deposited sequences of layered calcitic marls (Lake Sarnra) or laminated primary aragonite (Lake Lisan). The deposition of aragonite as the primary carbonate phase reflects the contribution of the incoming freshwater (loaded with bi-carbonate) and high Mg-, Ca-chloride brine that originated from the subsurface vicinity of the Dead Sea basin. Deposition of calcitic marls suggests a minor effect of the brines. The Ca-chloride subsurface brine has been migrating in and out of the wall rocks of the Dead Sea basin, reflecting the regional hydrological conditions. During most of the last glacial period and during the late Holocene, sufficient precipitation above the Judea Mountains pushed the subsurface Cachloride
Global Change Abstracts – The Swiss Contribution | Past Global Changes brines into the lakes causing the deposition of aragonite. During the Last Interglacial period the rain that precipitated above the Judea Mountains was insufficient to induce brine flow toward Lake Samra. It appears that sporadic floods provided calcium, bicarbonate and detritus to produce the Samra calcitic marls. Travertines deposited at the Samra-Lisan boundary indicate the early stage in the resumption of groundwater (springs) activity that led to the resurgence of Ca-chloride brine and rise of Lake Lisan. Similar variations in the regional rain precipitation and hydrological activity probably characterized the long-term geochetnical evolution of Pleistocene lacustrine waterbodies in the Dead Sea basin, enabling the use of the carbonates as paleo-hydrological monitors. Quaternary Science Reviews, 2007, V26, N17-18, SEP, pp 2219-2228. 08.1-376 16 000 years of vegetation and settlement history from Egelsee (Menzingen, central Switzerland) Wehrli M, Tinner W, Ammann B Switzerland Paleontology , History , Meteorology & Atmospheric Sciences , Plant Sciences Past vegetation dynamics and human impact from the Lateglacial to the present are reconstructed by pollen analysis of a core 12 in long from the raised bog Egelsee, central Switzerland (770 in a.s.l.). The depth-age model of the core is based on 29 AMS C-14 dates. The oldest dated macrofinssil has an age of 13 080 +/- 105 radiocarbon yr BP (15 370 cal. yr BP); extrapolation leads to a basal age of the core of 16 200 cal. yr BP. The biostratigraphy shows a typical vegetation development for Central Europe from open pioneer vegetation to Betula-Pinus forests in the Lateglacial, thermophilous mixed deciduous forests in the early Holocene, then mesophilous Abies-Fagus forests, and finally to the present cultural landscape. The initial population expansion of Abies alba may have coincided with climatic change at c. 8500 cal. yr BP. The mass expansion of Abies alba at 8 100 cal. yr BP may have been triggered by the 8.2-ka event and coincided with the empirical limit of Fagus silvatica, indicating initial population expansions. The succession of ecosystems with different plant composition is confirmed by detrended correspondence analysis (DCA): the main changes in the DCA axis I and 2 correspond to the transition phases between the different ecosystems. DCA axis I has an eigenvalue of lambda(1) = 0.46 and is significantly correlated (r = 0.82) to the non-arboreal pollen percentage curve. Rarefac- 181 tion analysis shows a high pollen diversity in the Lateglacial, lower pollen diversity in the Holocene before human impact, and increasing pollen diversity correlated with increasing human impact. Very little is known about the archaeology of the montane belt in central Switzerland. This study provides new data concerning human impact and settlement history in this area. Human activities are indicated by cereal pollen (earliest Hordeum/ Triticum type at 4700 cal. yr BP). Distinct pulses of anthropogenic forest clearances can be observed from the Neolithic period onwards. Holocene, 2007, V17, N6, SEP, pp 747-761. 08.1-377 Surface topography and ice flow in the vicinity of the EDML deep- drilling site, Antarctica Wesche C, Eisen O, Oerter H, Schulte D, Steinhage D Germany, Switzerland Cryology / Glaciology , Geomorphology , Paleontology Interpretation of ice-core records requires accurate knowledge of the past and present surface topography and stress-strain fields. The European Project for Ice Coring in Antarctica (EPICA) drilling site (75.0025 degrees S, 0.0684 degrees E; 2891.7 m) in Dronning Maud Land, Antarctica, is located in the immediate vicinity of a transient and forking ice divide. A digital elevation model is determined from the combination of kinematic GPS measurements with the GLAS12 datasets from the ICESat. Based on a network of stakes, surveyed with static GPS, the velocity field around the drilling site is calculated. The annual mean velocity magnitude of 12 survey points amounts to 0.74 m a(-1). Flow directions mainly vary according to their distance from the ice divide. Surface strain rates are determined from a pentagon-shaped stake network with one center point close to the drilling site. The strain field is characterized by along-flow compression, lateral dilatation and vertical layer thinning. Journal of Glaciology, 2007, V53, N182, pp 442-448. 08.1-378 Leaf area index for northern and eastern North America at the Last Glacial Maximum: a data-model comparison Williams J W, Gonzales L M, Kaplan J O USA, Switzerland Paleontology , Plant Sciences , Modelling , Meteorology & Atmospheric Sciences Aim To estimate the effects of full-glacial atmospheric CO 2 concentrations and climate upon
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