Search

Ecosystems damaged by distal volcanic ash and sulfur deposition usually recover within decades. However, sediment, stalagmite, and pollen records from the southernmost Andes indicate a 2000 yr impact on forest and aquatic ecosystems after deposition of a thin tephra layer. S[O.sub.2] released from altering pumice produced intense soil and lake acidification in a >150,000 [km.sup.2] area. Acidification led to nutrient leaching and affected soil microorganisms, causing plant decay and increased soil erosion in an area larger than 8000 [km.sup.2]. We conclude that weakly buffered soils in humid environments are extremely vulnerable to volcanic and anthropogenic acidification, causing long-lasting ecosystem damage and perturbations of paleoclimate proxy records. Keywords: volcanic impact, acidification, ecosystem.

Author(s): Holger Braun (corresponding author) [1]; Marcus Christl [1]; Stefan Rahmstorf [2]; Andrey Ganopolski [2]; Augusto Mangini [1]; Claudia Kubatzki [3]; Kurt Roth [4]; Bernd Kromer [1] Many palaeoclimate records [...]

A detailed study of growth periods of a flowstoue from Spannagel Cave in the Zillertal Alps (Austria) at ~2500 m above sea level, a site highly sensitive to climate changes, offers unprecedented new insights into Pleistocene climate change in Central Europe. Flowstone sample SPA 52 has a high U content (to 116 ppm); analyses of this sample reveal that episodes of calcite deposition started at 204 [+ or -] 3 ka, 135 [+ or -] 1.2 ka, and 122 ka, suggesting that at these times, the mean air temperature at this high Alpine site was within 1.5[degrees]C of the present-day condition. The beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 [+ or -] 2.5 ka, as deduced from the absolutely dated oxygen isotope curve in sediments from the Bahamas, as well as with recent coral evidence from Barbados indicating a high sea level already by 135.8 4 [+ or -] 0.8 ka. This set of data supports evidence against Northern Hemisphere forcing of termination II, because the insolation maximum is at 127 ka. Keywords: Pleistocene, interglacial, speleothems, uranium-series method, Alps.

U-Th age dating and stable isotope measurements of speleothems from Hoti Cave in northern Oman yield paleoclimate information from the region extending to 125 ka. The results (1) provide further confirmation of an early Holocene wet period in southern Arabia extending from some time prior to 9.7 ka and ending at 6.2 ka; (2) demonstrate a second period of wetness closely coinciding with the last interglacial period, marine isotope stage (MIS) 5e; (3) indicate that during MIS 5e, southern Arabia was considerably wetter than during the early Holocene; and (4) demonstrate that periods of increased monsoon wind strength, based on data from marine sediments, do not always coincide with evidence of greatly increased precipitation even from nearby continental areas.

A high-resolution multiparameter stratigraphy allows the identification of late Quaternary glacial and interglacial cycles in a central Arctic Ocean sediment core. Distinct sandy layers in the upper part of the otherwise fine-grained sediment core from the Lomonosov Ridge (lat 87.5 [degrees] N) correlate to four major glacials since ca. 0.7 Ma. The composition of these ice-rafted terrigenous sediments points to a glaciated northern Siberia as the main source. In contrast, lithic carbonates derived from North America are also present in older sediments and indicate a northern North American glaciation since at least 2.8 Ma. We conclude that large-scale northern Siberian glaciation began much later than other Northern Hemisphere ice sheets.