Volcanic and solar activity, and atmospheric circulation influences on cosmogenic 10 Be fallout at Vostok and Concordia (Antarctica) over the last 60 years

Details Volcanic and solar activity, and atmospheric circulation influences on cosmogenic 10 Be fallout at Vostok and Concordia (Antarctica) over the last 60 years Volcanic and solar activity, and atmospheric circulation influences on cosmogenic 10 Be fallout at Vostok and Concordia (Antarctica) over the last 60 years

Nov 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011gecoa..75.7132b&link_type=abstract

Geochimica et Cosmochimica Acta, Volume 75, Issue 22, p. 7132-7145.

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Scientific paper

The cosmogenic nuclide beryllium-10 ( 10 Be), recovered from ice cores, is often used to study solar activity on long timescales. However, the 10 Be signal is also influenced by factors other than the Sun. To identify and quantify various contributions to the 10 Be signal, two Antarctic snow records from the Vostok and Concordia sites spanning the last 60 years were studied at a sub-annual resolution. Three factors that contribute to the 10 Be signal were identified. First, a significant period of approximately 11 yr that can be associated with the modulation of 10 Be production by solar activity was detected in both records. The solar imprint constitutes 20-35% of the variance within the total signal. The 11-yr 10 Be snow component was attenuated by a factor of ˜0.5 and was delayed by ˜1.4 yr compared to the 10 Be production expected within the polar atmosphere. The result could be interpreted as the composite response of a stratospheric 10 Be reservoir with an 11-yr modulation that was attenuated and delayed (with respect to 10 Be polar production) and to a tropospheric 10 Be reservoir with an 11-yr modulation that was not attenuated or delayed. Then, peaks in 10 Be concentrations that were ˜66% and ˜35% higher than the average concentration were observed during the stratospheric volcanic eruptions of Agung (in 1963) and Pinatubo (in 1991), respectively. In light of these new results, published 10 Be ice core records could be reinterpreted because spikes in 10 Be concentration appear at the time of several stratospheric events. The data indicate that stratospheric volcanic eruptions can impact 10 Be transport and deposition as a result of the roles played by the sedimentation of sulfate aerosols and the formation and rapid settling of polar stratospheric clouds (PSC). Also, an interannual variability of ˜4 yr was determined in both 10 Be records, corresponding to ˜26% of the variance within the signal at Vostok. As with species of marine origin (sodium), this 4-yr variability is interpreted as a tropospheric modulation. The 4-yr variability could be associated with atmospheric circulation associated with the coupled Southern Ocean ocean-atmosphere system. The results presented here, from sites within the high Antarctic plateau, open new possibilities for ice core dating over the last few centuries and for the reconstruction of past solar activity in relation to climate.

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