Late Holocene environmental ice core record from Akademii Nauk ice cap (Severnaya Zemlya)

Ice cores are established as archives for environmental changes since many years. On Severnaya Zemlya, the easternmost archipelago with considerable glaciation in the Eurasian Arctic, a 724 m long ice core has been drilled on Akademii Nauk the largest ice cap there. Stable water isotope and major ions concentrations in this ice core are presented (e.g. Fritzsche et al., 2005, Opel et al., 2013). They represent more than 3000 years of regional climate and environmental history. A well‐known depth‐age relationship is necessary for a paleoclimate interpretation of the data. In a first approach the dating was performed by counting of annual cycles of stable isotopes well‐preserved in the core even though overprinted by the effect of percolating melt water from summer surface melting. The depth‐age scale produced by counting has been matched to volcanic eruption events with well‐known ages detectable in the sulphate record of the core. This approach has some disadvantages due to the fact that the pattern of stratospheric volcanic events recorded in well‐dated ice cores from Greenland and Antarctica is influenced by rather regional tropospheric eruptions as in our case probably in Iceland and Kamchatka, partly less precisely dated. The depth‐age relationship has therefore to be proofed by an independent method.
The isotope ¹⁰Be is produced by cosmic radiation in the Earth’s atmosphere. Its residence time there is about one year, shorter than it is for ¹⁴C, for which reason variability of ¹⁰Be in archives like glaciers is much higher compared to ¹⁴C. The production rate of both radionuclides is depending on the solar activity. Their concentrations were used for the reconstruction of heliomagnetic variations in the past and can be vice versa used for dating of ice cores.
Today, accelerator mass spectrometry (AMS) allows measurements of ¹⁰Be in ice cores. Its concentration is depending on the geomagnetic coordinates of the location of its production, transport and deposition mechanisms, accumulation rates etc. Therefore, local differences in ¹⁰Be concentrations are observed (Berggren et al., 2009). Here, we present ¹⁰Be concentrations measured by the team of DREsden AMS (DREAMS) (Akhmadaliev et al., 2013) in discrete Akademii Nauk ice core samples of about 300 g. Our ¹⁰Be record shows its general potential to validate our depth‐age model matching the ¹⁰Be concentration pattern to that of Greenlandic ice cores as well as ¹⁴C production reconstruction.
References
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