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Climate of North Siberia during the last 2500 years: an ice-core record from Akademii Nauk ice cap (Severnaya Zemlya)

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Citation:
Fritzsche, D. , Schütt, R. , Opel, T. , Meyer, H. , Miller, H. and Wilhelms, F. (2005): Climate of North Siberia during the last 2500 years: an ice-core record from Akademii Nauk ice cap (Severnaya Zemlya) , 22. Internationale Polartagung, 18-24 Sept., Jena, Germany. .
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Abstract:

Akademii Nauk is one of the largest Arctic ice caps outside of Greenland. The first ice core was drilled there in 1986/87 by a Russian team. A Late Pleistocene basal age was assumed for this core. A new 724 m long core was drilled on Akademii Nauk between 1999 and 2001 to get climate information for the whole Holocene in high resolution. The project was funded by the Federal Ministry of Education and Research (BMBF) and performed in co-operation of the Alfred Wegener Institute for Polar and Marine Research with the Arctic and Antarctic Research Institute and the Mining Institute in St. Petersburg.Arctic ice cores outside of central Greenland are characterized by melt-layers caused by melting and even by rain during summertime especially when drilling sites are at relatively low altitude. Special methods were developed recently for interpretation of electrical conductivity, isotopic variations and chemical composition data of ice cores from Svalbard, Franz Josef Land, Canada and Severnaya Zemlya.We present our results of core dating, the isotopic profile and the interpretation of melt-layer content for the new Akademii Nauk ice core. Isotope data are available in high resolution for the uppermost 136 m of core representing approx. the last 275 years. The dating of the core was done using seasonal variations in isotopic and electrical conductivity records. Signals of historical volcano eruptions are used as additionally dating points. By this method we found a basal age of approx. 2,650 years for the centre of Akademii Nauk. The present-day annual accumulation rate is about 460kgm-2 there. The mean air temperature close to the surface was -15.7°C from May 1999 to April 2000. The firn temperature was -10.2°C measured in April 2000 at 10 m depth. It reflects the influence of latent heat released by refreezing of melt water in the firn. The observed annual layer thicknesses indicate a positive annual net mass balance of the ice cap until the recent years at least. The altitude of the glacier surface increased what has been considered in the climate interpretation of the data. The lowest temperature was found about 1790 the 20th century was the warmest in the whole record.The trend of d18O, especially the 11 year running mean, correlates quite well (r=0,93) with the temperature record of Vardö/North Norway, situated 2,000 km south-western of the ice cap. This is a hint that our isotopic data describe the climate/temperature trend at least of the westerly Eurasian Artic.C-axis analysis of the ice crystals shows an increased crystal orientation with depth.

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