The early days of SMIA in perspective

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Solar and Atlantic Ocean Influence on Climate of Fennoscandia

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Deuterium–hydrogen ratios, electrical conductivity and nitrate for high-resolution dating of polar ice cores

In order to support the very high time resolution required to observe short-term variations in nitrates and all other ions represented by electrical conductivity in polar ice, a Fourier transform infrared spectrometer was developed for measurement of deuterium concentration in ice samples, as an additional support for the timescale of ultra-high resolution. The portable instrument provided the possibility to measure deuterium concentration on exactly the same samples as used for measuring nitrate concentrations and liquid electrical conductivity, thus verifying that the original dating of the annual variations in nitrate was correct. We present basic information about how the high-resolution data were obtained and discuss their reliability and significance.Peer reviewe

Biases in radiocarbon dating of organic fractions in sediments from meromictic and seasonally hypoxic lakes

We present here radiocarbon dating results from two boreal lakes in Finland, which are permanently (meromictic) or seasonally stratified and contain continuous sequences of annually laminated sediments that started to form in the early Holocene. The radiocarbon dating results of different organic components were compared with the varve-based sediment chronologies. The deviation between the Lake Valkiajarvi varve chronology (8400 varve years 2-3% error estimate) and 33 C-14 dates taken from insoluble and soluble organic phases vary inconsistently throughout the Holocene. In extreme cases mean calibrated radiocarbon dates with 95.4% confidence levels (2 sigma) are -2350 and +2040 years offset when compared with the varve chronology. On average, the radiocarbon dates are offset by ca. +550 years. The deviation between the Lake Nautajarvi varve chronology (9898 varve years +/- 1% error estimate) and 26 C-14 dates analyzed with conventional and AMS methods indicates that radiocarbon dates are systematically older by 500-1300 years (about 900 years on average). This significant offset mean that radiocarbon dates obtained from organic bulk sediment of meromictic and seasonally hypoxic lakes must be cautiously interpreted because of the reservoir effect and carbon cycling at the sediment-water interface. Direct evidence was obtained from the dating of soluble fraction and insoluble organic matter from near bottom water in the monimolimnion of Lake Valkiajarvi, which yielded C-14 ages of 560 +/- 80 BP and 2070 +/- 140 BP, respectively. Our study reinforces previous results that age-depth models based on bulk sediment radiocarbon dates obtained on sediments of stratified lakes are of limited value for accurate dating of changes in land use and especially the commence of agriculture.Peer reviewe

Dieten hos barn och vuxna i Westerhus: Data från spårämnen, kolisotoper och odontologi

The diet for adults and children at Westerhus. Data from trace element and carbon isotope analyses and odontology By Elisabeth Iregren, Högne Jungner, Jyrki Räisänen and Verner Alexandersen The individuals from Westerhus were randomly selected to cover all age groups and both sexes. Bone samples were taken from 94 skeletons (25%) of the population. Different skeletal elements have been used in the PIXE (Proton Induced X-ray Emission) analyses. The following elements were studied: Ca (calcium), the earth metals Mn (manganese) and Fe (iron); the trace elements Zn (zinc), Sr (strontium) and Cr (chromium); the heavy metal Pb (lead) and further Cu (copper), Br (bromine), Ni (nickel), Mo (molybdenum), Zr (zirconium). Soil samples were examined as well as several bone samples of a few individuals. In Westerhus no severe influence of heavy metals has been traced. Lead is found in small amounts in the skeletons. Compared to other medieval people the values of zink indicate a low intake of animal protein in the Westerhus population. Copper is also found in very low amounts. This proves that they did not consume any marine food at all. When using the definitions by Johansen et al. (1986) for evaluating the values of the carbon isotopes, we may conclude that the individuals were presumably consumers of mainly terrestrial food. Thus, the data on carbon isotopes, zinc, and copper verify one another. Results on the Sr/Ca in the diet and the bearing on weaning are presented. It is highly likely that most children in Westerhus were given human milk until the age of 2 years. Single individuals show, however, signs of enamel hypoplasia, which indicates that a few children were given supplementary food earlier. Above the age of two the variation between individuals increases, hinting to different feeding practices in different families. We believe that some children were not weaned until the age of 3-4 years, but above the age of 5 the children show Sr/Ca-values similar to the adults. Swärdstedt (1966) studied adults and found that the number of enamel hypoplasia increased markedly in Westerhus during the years 2.5-4. Evidently, this period in life was critical even to those who survived infancy

Does the age of fine root carbon indicate the age of fine roots in boreal forests?

To test the reliability of the radiocarbon method for determining root age, we analyzed fine roots (originating from the years 1985 to 1993) from ingrowth cores with known maximum root age (1 to 6 years old). For this purpose, three Scots pine (Pinus sylvestris L.) stands were selected from boreal forests in Finland. We analyzed root 14C age by the radiocarbon method and compared it with the above-mentioned known maximum fine root age. In general, ages determined by the two methods (root 14C age and ingrowth core root maximum age) were in agreement with each other for roots of small diameter (<0.5mm). By contrast, in most of the samples of fine roots of larger diameter (1.5-2mm), the 14C age of root samples of 1987-89 exceeded the ingrowth core root maximum age by 1-10 years. This shows that these roots had received a large amount of older stored carbon from unknown sources in addition to atmospheric CO2 directly from photosynthesis. We conclude that the 14C signature of fine roots, especially those of larger diameter, may not always be indicative of root age, and that further studies are needed concerning the extent of possible root uptake of older carbon and its residence time in roots. Keywords: fine root age, Pinus sylvestris, radiocarbon, root carbon, ingrowth cores, tree ringPeer reviewe