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Late Holocene climate change in the Eurasian Arctic - Evidence from Akademii Nauk ice core (Severnaya Zemlya)

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Citation:
Opel, T. , Fritzsche, D. and Meyer, H. (2009): Late Holocene climate change in the Eurasian Arctic - Evidence from Akademii Nauk ice core (Severnaya Zemlya) , Jahrestagung der Arbeitsgemeinschaft Stabile Isotope, 5.-7. Oktober 2009, Alfred-Wegener-Institut für Polar- und Meeresforschung in Potsdam. .
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Abstract:

Ice cores are well known as one of the best archives for providing information on paleoclimatic and paleoenvironmental changes on different temporal and spatial scales. A 724 m deep ice core was drilled recently on the relatively low-altitude Akademii Nauk (AN) ice cap (Severnaya Zemlya) to gain high resolution paleoclimatic information from the Central Russian Arctic. The AN ice core provides significant proxy data for the reconstruction of regional climate and environmental changes; although the ice cap is affected by strong summertime melt water infiltration. We present data of stable water isotopes (δ18O, deuterium excess d), melt-layer content and major ions of the upper 535 m, covering about 1 700 years in an annual to multi-annual resolution. The core chronology is based on volcanic reference layers and stable-isotope annual layer counting.The AN δ18O data are highly correlated to instrumental temperature data from the Western Eurasian Arctic and can therefore be used as valuable near-surface temperature proxy for this region. The long-term decrease of AN δ18O and also sea salt ion concentrations reflects the growth of AN ice cap over large parts of the Late Holocene. AN δ18O data reveal major temperature changes in the last centuries, particularly rapid warming and cooling events in the 15th and 16th centuries, the absolute minimum around 1800 and the exceptional warming to the double-peaked early 20th century maximum, which represents the absolute temperature maximum in the Late Holocene. These changes indicate considerable shifts in atmospheric circulation patterns, accompanied by sea ice extent changes. However, no pronounced Medieval Warm Period or Little Ice Age is visible in our AN data. Generally, AN δ18O values coincide well with that of the Austfonna ice core (Svalbard), underlining the regional significance of AN ice core data.In the 20th century, AN d excess variations are connected with regional sea ice extent changes. Low sea-ice extent allows a higher contribution of regional moisture, leading to lower d excess due to colder evaporation conditions. In turn, a high sea-ice extent prevents a considerable regional moisture contribution to the precipitation on Akademii Nauk ice cap, which is therefore characterized by higher d excess values. This pattern indicates that d excess can provide information on the proportion of regional moisture in the precipitation and therefore on regional sea ice extent changes.The major ion concentrations in AN ice core reflect the atmospheric aerosol content. Warmer periods show evidence of higher sea-salt ion concentrations due to less sea-ice extent. Outstanding peaks in sulphate represent major volcanic eruptions. The 20th century ion records indicate major shifts in atmospheric circulation and significant anthropogenic pollution.

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