The potential for a continuous 10Be record measured on ice chips from a borehole

Results in geochemistry(2021)

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摘要
• We test the preparation and measurement of small 10 Be samples from continuous ice chips from a borehole in East Antarctica. • The ice chips were recovered using a rapid drill method developed recently by the British Antarctic Survey. • Accelerator Mass Spectrometry (AMS) for 10 Be yielded very precise results for small samples weighing 25 to 45g • The resulting 10 Be concentration reflects well the atmospheric production signal of 10 Be during 1354 – 2017. • This novel ice chip sample will benefit the study of local effects on the 10 Be deposition and better global estimates of the 10 Be production rate. Ice cores are excellent archives for obtaining long and continuous 10 Be records. However, traditional ice core 10 Be measurements required a lot of ice (0.5–1kg) and often needed to be connected to a large and costly ice core project. These reasons have been the factors limiting the number and variety of 10 Be projects and data. In this paper, we show measurements of 10 Be on small samples (∼45g) of continuous auger ice chips from a borehole at Little Dome C (LDC), East Antarctica. The sample preparation method for 10 Be accelerator mass spectrometry (AMS) was tested and optimized using test samples (∼50g) including well-mixed surface ice chips from the LDC site, snow collected in Lund (Sweden) and frozen Milli-Q water. The results show that our small ice samples should be processed without ion exchange filtration of the melt water and cleaning the subsequent Be(OH) 2 precipitate. In addition, co-precipitating Be with Fe led to more reproducible measurement currents and offer the potential for higher efficiency and precision via longer measurement time. We applied the established preparation method to measure 10 Be on 76 samples of the auger ice chips. The resulting 10 Be concentration record for the period from 1354 to 1950 CE agrees well with the 10 Be concentration in a South Pole ice core and the global 14 C production rate and thus reflects well the atmospheric production signal of 10 Be. We also observed insignificant mixing among the ice chip samples during the process of drilling and retrieving the ice. Therefore, the new ice chip samples are promising for assessing the long-term changes in 10 Be deposition at different ice core sites. A wide application of this novel ice chip samples will increase the variety of 10 Be records which will help to improve the assessment of long-term solar and geomagnetic shielding of galactic cosmic rays.
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关键词
AMS,Sample preparation,Beryllium 10,Ice core,Solar activity
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