The role of the sun on Earth's climate variability is still much debated. Here we present an ice core oxygen isotope record from the continental Siberian Altai, serving as a high‐resolution temperature proxy for the last 750 years. The strong correlation between reconstructed temperature and solar activity suggests solar forcing as a main driver for temperature variations during the period 1250–1850 in this region. The precisely dated record allowed for the identification of a 10–30 year lag between solar forcing and temperature response, underlining the importance of indirect sun‐climate mechanisms involving ocean‐induced changes in atmospheric circulation. Solar contribution to temperature change became less important during industrial period 1850–2000 in the Altai region.
Total Hg and MMHg concentrations were assessed in more than 350 fish and shellfish samples. Hg concentrations in Greater North Sea fish of prey range from 0.039 mg kg(-1) wet weight (ww; for ray) to 0.61 mg kg(-1) ww (for dogfish) and for all other fish species, from 0.045 mg kg(-1) ww (for plaice) to 0.33 mg kg(-1) ww (for sand sole), with 95 +/- 2% of the Hg content in the MMHg form. In Belgian coastal zone, fish concentrations range from 0.063 mg kg(-1) ww for plaice to 0.13 mg kg(-1) ww for flounder, with 82-87% of the Hg content in the MMHg form. In fish of the Scheldt, which is a very polluted estuary, Hg levels, as well as the percent MMHg of the total Hg, were lower than in the two zones previously mentioned. The intraspecies variability is of the order of 50% in each of the three zones. In liver tissue, a much larger variability was observed than in muscle tissue, except for fish species of the Scheldt. In most cases, the MMHg fraction in a particular fish species is inversely related to the intraspecies variability. Bioconcentration and biomagnification factors (BCF and BMF, respectively) were assessed. MMHg-BMFs were a few orders of magnitude higher than Hg(inorganic)-BMFs, and for the same species were always highest in the Greater North Sea and lowest in the Scheldt. For each of the Belgian coastal zone four species, a weak positive correlation between Hg content and fish length was found; however, the larger the size-range, the better the correlation. Taking fish length into account, a statistically significant difference in contamination level was observed for species sampled from the different geographical zones.
In July 2001, a 140 m long ice core was recovered from the Belukha glacier (49°48′26″N, 86°34′43″E, 4062 m a.s.l.) in the Siberian Altai. The ion chemistry of the upper 86 m, covering the last two centuries, is characterized by biogenic emissions (ammonium and formate), aeolian dust (calcium, magnesium, chloride, and sodium) and anthropogenic species (sulfate, nitrate, and ammonium). Particularly high ammonium and formate concentrations indicate pronounced emissions from Siberian forests. The inferred fire frequency does not show a long‐term trend but distinct periods of enhanced activity. Sulfate has the highest industrial to preindustrial ratio and an anthropogenic contribution of more than 80%. Variations in this record reflect sulfur dioxide emissions in Siberia and Kazakhstan. Sulfate concentrations remained low until 1950, then sharply increased and peaked in the 1970s. The decrease in the 1980s is attributed to the economic, political, and social crises and to the replacement of coal with gas. Rising nitrate concentrations since 1960 reflect traffic growth and enhanced fertilizer application. Increasing ammonium concentrations since the 1950s are attributable to population inflow in southern Siberia with the associated enhancement of agricultural activity. A nitrate peak of short duration in 1908 is thought to be the atmospheric signature from the Tunguska event on 30 June 1908.
Emissions from forests represent an important source of gaseous precursors of aerosols that can significantly alter the regional radiation balance. Long‐term records of biogenic emissions are available for Northern America and the Amazon Basin, whereas the historical development of emissions from Siberian forests, comprising about 20% of the world's forested area, is unknown so far. Here we investigate ice core ammonium and formate records for the last 750 years, representing biogenic emissions from boreal Siberian forests in the pre‐industrial era. Biogenic emissions were found to be closely related to changes in temperature following variations in solar activity. In addition, anthropogenic emissions have caused a strong increase of the ammonium concentrations and a drop of the formate concentrations in the last 60 years.
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