In the Eurasian Arctic, the archipelago of Severnaya Zemlya is the easternmost one which is covered by considerable ice caps. This gives the opportunity to get regional paleo-climate information from ice core records. In 1986/87 the first ice core was drilled on Akademii Nauk ice cap, the northernmost one on Severnaya Zemlya (Savatyugin and Zagorodnov (1988), Klement'yev et al. (1991)). This core was analyzed with relatively low data resolution. A chronology was published by Klement'yev et al. (1988 and 1991) and Kotlyakov et al. (1990). These authors claimed a Late Pleistocene bottom age for this core. From 1999 to 2001 a new 724 m long ice core was drilled on Akademii Nauk to proof the maximum resolution possible to be obtained and to check the time-scale published so far for this glacier (Savatyugin et al. (2001), Fritzsche et al. (2002)). This project was carried out in co-operation between the Alfred Wegener Institute (AWI), Germany, the Arctic and Antarctic Research Institute (AARI) St. Petersburg and the Mining Institute St. Petersburg, Russia. The knowledge of annual layer thickness is the basis for the chronology of the core. One of the main problems is that infiltration processes caused by melting and even rain during summer time will smooth or destroy seasonal signals. The variation of stable isotopes of water (dD and d18O) is the most common tool to reconstruct the annual layer thickness also in areas with percolation as Pohjola et al. (2002) have demonstrated but sometimes oscillations in D-excess values better resolve the annual variation (Stichler et al. (1979)). We used D-excess and d18O for determination of layer thickness.A recent mean accumulation rate of about 460 kgm-2a-1 was found at the drilling site close to the summit of Akademii Nauk using horizons with increased 137Cs radioactivity as time markers. Pinglot et al. (2003) have found two such peaks coursed by nuclear weapon tests in the beginning of 1960s and by the accident of Chernobyl nuclear power station in 1986. Zagorodnov et al. (1990) reported the same value of 460 kgm-2a-1 as mean accumulation rate of two years of observation (1986/87) in the area of station 'Mir' at summit on the Akademii Nauk ice cap. The data of electrical conductivity, d18O and melting content are published by Fritzsche et al. (2005) in high resolution for the upper 136 m of the new drilled ice core. These data cover about 275 years following the preliminary dating basing on counting of annual variations of D-excess and d18O supported by peaks in the electrical conductivity signal, assumed to be produced by historical volcano eruptions. The highest peak in electrical conductivity was found in a depth of 25.79-25.94 m connected with huge increased nss SO4-2 content observed by ion chromatographic analyses of the dissolvable constituents. This indicates that this horizon was influenced by a volcano event most likely the eruption of Bezimyanny in 1956. Weiler et al. (2005) confirmed the recent mean accumulation rate by core chemistry studies. The annual layer thickness is decreasing with depth because of thinning under the pressure of the upper layering ice. An annual layer thickness of approx. 11 cm could be observed close to the bottom using stable isotope variations. We have calculated a basal age of approx. 2500 years for the Akademii Nauk ice cap interpolating the annual layer thickness between the upper part of the core studied in detail and the range close to the bottom were data are available in high resolution. Counting of electrical conductivity cycles results in a bottom age of 2650 years. In this calculation we assume that annual layers were never eroded by melting. This age and the annual layer thickness we found can be explained only giving up an equilibration assumption for the Akademii Nauk ice cap at least for the past. That means we assume that the glacier was growing up to its today's altitude from an initial stage almost at sea level. This has to be considered for paleo-climate interpretation of d18O data.Fig.1. Comparison between d18O records from Academii Nauk ice cap (30 years running mean), Hans Tausen ice cap (North Greenland) and GRIP (summit of Central Greenland). For Akademii Nauk the data are corrected assuming an altitude effect coursed by a growing of the ice capThe oxygen isotope data of the Akademii Nauk ice core drilled in 1999/2001 are shown in Fig. 1 using our preliminary chronology. The d18O values had been corrected assuming a continuous growing of the ice cap and an altitude effect of 4per mil/100m. The data show the trend of temperature of the last 2500 years on Akademii Nauk ice cap. They are indicating a relatively warm period about 2300 - 2400 years BP followed by a relatively long lasting colder time span with minima at about 300 AD and 1800. The little ice age couldn't be found as a characteristically drop down in temperature but a dramatically warming was observed since app. 1800. Kotlyakov et al. (2004) found this warming for the same period in surface temperatures reconstructed from temperature depth profile of the drill on Akademii Nauk in 1986/87. Since 1875 the warming is documented in meteorological data for the whole Eurasian Arctic. Similarities like this warming were found in d18O values from Hans Tausen ice cap (North Greenland) and Akademii Nauk (Fig.1) which could not be observed in the record from Central Greenland (GRIP). It makes clear that summit of the Greenland ice cap has special climate conditions which not necessarily reflect climate changes in the maritime Arctic at least in Late Holocene. Such changes seem to be stronger in lower altitude and smaller size of the ice cap.The drilling project was funded by the German Ministry of Education and Research (03PL027A/3).ReferencesSavatyugin, A.M., Zagorodnov, V.S. (1988) Glyatsiologicheskiye issledovaniya na lednikovom kupole Akademii Nauk [Glaciological studies on the Academy of Sciences ice cap]. Mater. Glyatsiol. Issled. 61, 228Klement¡Çyev, O.L., Potapenko, V.Yu., Savatyugin, L.M., Nikolaëv, V.I. (1991) Studies of the internal structure and thermal-hydrodynamic state of the Vavilov glacier, Archipelago Severnaya Zemlya. - International Association of Hydrological Sciences Publication vol. 208 (Symposium at St. Petersburg 1990 - Glaciers-Ocean-Atmosphere Interactions), 49-59Klement'yev, O.L., Korotkov, I.M., Nikolaëv, V.I. (1988) Glyatsiologicheskiye issledovaniya v 1987-1988gg. na lednikovakh kupolakh Severnoy Zemli [Glaciological studies on the ice domes of Severnaya Zemlya in 1987-88]. Mater. Glyatsiol. Issled. 63, 25-26Kotlyakov, V.M., Zagorodnov, V.S., Nikolaev, V.I. (1990) Drilling on ice caps in the Soviet Arctic and on Svalbard and prospects of ice core treatment. - In: Kotlyakov, V.M., Sokolov, V.Ye. (eds.): Arctic Research, Nauka, Moscow, 5-18Savatyugin, L.M., Arkhipov, S.M., Vasilyev, N.I., Vostretsov, R.N., Fritzsche, D., Miller, H. (2001) Rossiysko-germanskiye glyatsiologicheskiye issledovaniya na Severnoy Zemle i prilegayushchikh ostrovakh v 2000 g. [Russian-German glaciological studies on Severnaya Zemlya and adjacent islands in 2000]. Mater. Glyatsiol. Issled. 91, 150-162Pohjola V.A., Martma, T.A., Meijer, H.A.J., Moore, J.C., Isaksson, E., Veikmäe, R. van de Wal, R.S.W. (2002) Reconstruction of three centuries of annual accumulation rates based on the record of stable isotopes of water from Lomonossovfonna, Svalbard. - Annals of Glaciology, v. 35, 57-62Stichler, W., Baker, D., Oerter, H., Trimborn, P. (1982) Core drilling on Vernagtferner (Oetztal Alps, Austria) in 1979: Deuterium and oxygen-18 contents. Zeitschrift für Gletscherkunde und Glazialgeologie, Bd. 18, Ht. 1, 23-35Pinglot, J.F., Vaikmäe, R.A., Kamiyama, K. and 11 others (2003) Ice cores from Arctic sub-polar glaciers: chronology and post-depositional processes deducted from radioactivity measurements. Journal of Glaciology, v. 49, No.164, 149-158Zagorodnov, V.S., Klement'yev, O.L., Nikiforov, N.N., Nikolaëv, V.I., Savatyugin, L.M., Sasunkevich, V.A. (1990) Gidrotermicheskiy rezhim i l'doobrazovaniye v tsentral'noy chasti lednika Akademii Nauk na Severnoy Zemle [Hydrothermal regime and ice formation in the central part of the Akademiya Nauk glacier, Severnaya Zemlya]. Mater. Glyatsiol. Issled. 70, 36-43Fritzsche, D., Schütt, R., Meyer, H., Miller, H., Wilhelms, F., Opel, T., Savatyugin, L.M., (2005) A 275 year ice core record from Akademii Nauk ice cap, Severnaya Zemlya, Russian Arctic. - Annals of Glaciology, v. 42, (accepted)Weiler, K., Fischer, H., Fritzsche, D., Ruth, U., Wilhelms, F., Miller, H. (2005) Glaciochemical reconnaissance of a new ice core from Severnaya Zemlya. J. Glaciol. (in press)Kotlyakov, V.M., Arkhipov, S.M., Henderson, K.A., Nagornov, O.V. (2004) Deep drilling of glaciers in Eurasian Arctic as a source of paleoclimatic records. Quaternary Science Reviews 23, 1371-1390
AWI Organizations > Geosciences > Periglacial Research
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Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene