Affine Toda field theory on a half line

The question of the integrability of real-coupling affine toda field theory on a half-line is addressed. It is found, by examining low-spin conserved charges, that the boundary conditions preserving integrability are strongly constrained. In particular, for the $a_n\ (n>1)$ series of models there can be no free parameters introduced by the boundary condition; indeed the only remaining freedom (apart from choosing the simple condition $\partial_1\phi =0$), resides in a choice of signs. For a special case of the boundary condition, it is argued that the classical boundary bound state spectrum is closely related to a consistent set of reflection factors in the quantum field theory.Comment: 16 pages, TEX (harvmac), DTP-94/7, YITP/U-94-1

Evidence for a bi-partition of the Younger Dryas Stadial in East Asia associated with inversed climate characteristics compared to Europe

The Younger Dryas Stadial (YDS) was an episode of northern hemispheric cooling which occurred within the Last Glacial Interglacial Transition (LGIT). A major driver for the YDS climate was a weakening of the Atlantic Meridional Overturning Circulation (AMOC). It has been inferred that the AMOC began to strengthen mid-YDS, producing a bipartite structure of the YDS in records from continental Europe. These records imply that the polar front and westerlies shifted northward, producing a warmer second phase of the YDS in Europe. Here we present multi-proxy data from the sediments of Lake Suigetsu (Japan), as evidence that a related bi-partition of the YDS also occurred in East Asia. Besides showing for the first time that the bi-partition was not limited to the North Atlantic/European region, the data also imply a climatic dipole between Europe and East Asia since the cold-warm characteristics are reversed at Lake Suigetsu. We suggest that changes in eastward moisture transport from the North Atlantic are the primary mechanism by which the teleconnection can be explained

Hydrological (in)stability in Southern Siberia during the Younger Dryas and early Holocene

Southern Siberia is currently undergoing rapid warming, inducing changes in vegetation, loss of permafrost, and impacts on the hydrodynamics of lakes and rivers. Lake sediments are key archives of environmental change and contain a record of ecosystem variability, as well as providing proxy indicators of wider environmental and climatic change. Investigating how hydrological systems have responded to past shifts in climate can provide essential context for better understanding future ecosystem changes in Siberia. Oxygen isotope ratios within lacustrine records provide fundamental information on past variability in hydrological systems. Here we present a new oxygen isotope record from diatom silica (ẟ18Odiatom) at Lake Baunt (55°11′15″N, 113°01,45″E), in the southern part of eastern Siberia, and consider how the site has responded to climate changes between the Younger Dryas and Early to Mid Holocene (ca. 12.4 to 6.2 ka cal BP). Excursions in ẟ18Odiatom are influenced by air temperature and the seasonality, quantity, and source of atmospheric precipitation. These variables are a function of the strength of the Siberian High, which controls temperature, the proportion and quantity of winter versus summer precipitation, and the relative dominance of Atlantic versus Pacific air masses. A regional comparison with other Siberian ẟ18Odiatom records, from lakes Baikal and Kotokel, suggests that ẟ18Odiatom variations in southern Siberia reflect increased continentality during the Younger Dryas, delayed Early Holocene warming in the region, and substantial climate instability between ~10.5 to ~8.2 ka cal BP. Unstable conditions during the Early Holocene thermal optimum most likely reflect localised changes from glacial melting. Taking the profiles from three very different lakes together, highlight the influence of site specific factors on the individual records, and how one site is not indicative of the region as a whole. Overall, the study documents how sensitive this important region is to both internal and external forcing

Oxygen isotope composition of diatoms from sediments of Lake Kotokel (Buryatia).

This is a summary of new oxygen isotope data for diatoms from Lake Kotokel sediments, with implications for responses of the lake system and its environment to global change over the past 46 kyr. Fossil diatoms in all samples are free from visible contamination signatures and contain no more than 2.5% Al2O3, which ensures reliable reconstructions. The δ18O values in diatoms vary between +23.7 and +31.2‰ over the record. The results mainly represent diatom assemblages of summer blooming periods, except for the time span between 36 and 32 kyr, when the isotopic signal rather records a shift from summer to spring blooming conditions. Possible water temperature changes only partly explain the changes in the isotopic record. The observed isotopic patterns are produced mainly by isotope changes in lake water in response to variations in air temperature, hydrology, and atmospheric circulation in the region. During Marine Isotope Stage (MIS) 2 (Last Glacial maximum), high δ18Odiatom resulted from rapid evaporation and low fluvial inputs. The high δ18O values of about +29 to +30‰ during the first half of MIS 1 (Holocene interglacial) suggest an increased share of summer rainfalls associated with southern/southeastern air transport. The δ18O decrease to +24‰ during the second half of MIS 1 is due to the overall hemispheric cooling and increased moisture supply to the area by the Atlantic transport. The record of Lake Kotokel sediments provides an example of complex interplay among several climatic controls of δ18Odiatom in the Late Pleistocene and the Holocene

Vegetation and climate changes around the Lama Lake, Taymyr Peninsula during the Late Pleistocene and Holocene reconstructed from pollen records

A continuous lacustrine sequence from the western part of Lama Lake (69°32'N, 90°12'E),completed by a peat sequence from the lake catchment provides the first detailed environmentalreconstruction for the Late Glacial and Holocene on the Taymyr Peninsula. Scarce steppe-likecommunities with Artemisia, Poaceae, and Cyperaceae dominated during the Late Glacial. Tundra-like communities with Betula nana, Dryas, and Salix grew on more mesic sites. There are distinctclimatic signals, which may be correlated with the Bølling and Allerød warmings and Middle andYounger Dryas coolings. The Late Glacial/Preboreal transition, at about 10,000 14C yr BP, wascharacterized by changes from predominantly open herb communities to shrub tundra ones. Larchforest might have been established as early as 9700-9600 14C yr BP, whilst shrub alder came tothe area ca 9500-9400 14C yr BP, and spruce did not reach area before ca 9200 14C yr BP. Spruce-larch forests with shrub alder and tree birch dominated the vegetation around the Lama Lake fromca 9000 14C yr BP. Dwarf birch communities were also broadly distributed. Role of spruce in theforest gradually decreased after 4500 14C yr BP. Vegetation cover in the Lama Lake area becamesimilar to modern larch-spruce forest ca 2500 14C yr BP. A pollen-based biome reconstructionsupports a quantitative interpretation of the pollen spectra. Climate reconstructions obtained withinformation-statistical and plan-functional-type methods show very similar trends in reconstructedJuly temperature since ca 12,300 14C yr BP, while precipitation anomalies are less coherent,especially during the Late Glacial-Holocene transition

Yangshao – 100 Jahre chinesische Archäologie

„Yangshao“ ist der Name des Fundplatzes, den der schwedische Geologe J. G. Andersson 1921 begann freizulegen und mit dem fortan die erste jungsteinzeitliche Kultur Chinas bezeichnet wurde. Die Autoren dieses Beitrags haben chinesische Kollegen gefragt, was heute für sie die Yangshao-Kultur ausmacht, welche Fundplätze sie für die wichtigsten halten und warum, welche Innovationen sie mit ihr verbinden und welche Bedeutung Yangshao im Gesamtgefüge aller jungsteinzeitlichen Kulturen zukommt

Atlas of pollen, spores and further non-pollen palynomorphs recorded in the glacial-interglacial late Quaternary sediments of Lake Suigetsu, central Japan

Abstract not availableDieter Demske,Pavel E. Tarasov,Takeshi Nakagawa, Suigetsu 2006 Project Member