A Comparison of ³⁶Cl Nuclear Bomb Inputs Deposited in Snow From Vostok and Talos Dome, Antarctica, Using the ³⁶Cl/Cl⁻ ratio

Abstract

36Cl production in the atmosphere is modulated by the magnetic field intensity of both the Sun and the Earth. The record of 36Cl concentration along with that of 10Be in ice cores may therefore provide information as to their variability. To better understand the 36Cl signal in glaciological archives, we measured its concentration in Talos Dome snow samples (mean accumulation rate of 8 g cm−2 year−1 water equivalent) spanning the 1910 to 1980 CE period with a resolution of one sample every 3 years from 1955 to 1980 C.E., and in Vostok snow samples (mean accumulation rate of 1.96 g cm−2 year−1 water equivalent) spanning the 1949 to 2007 CE period with a 6‐month resolution that had never before been obtained. Marine nuclear bomb tests in the late 1950s produced anthropogenic 36Cl, which was injected into the stratosphere and spread around the globe. In the late 1950s this anthropogenic pulse led to an increase of 36Cl concentration at Talos Dome that was more than 100 times higher than the prebomb and postbomb values. It is noteworthy that the atmosphere of Vostok remains polluted by anthropogenic 36Cl today. This pollution results from gaseous H36Cl mobility at low accumulation sites and implies re‐emission of 36Cl from the snowpack that is not observed at Talos Dome. The 36Cl/Cl− ratio may be used to discriminate the stratospheric anthropogenic 36Cl source from the tropospheric natural 36Cl source, which allows us to discuss the immobile vs. mobile 36Cl in the Vostok snowpack.

High‐Resolution 10Be and 36Cl Data From the Antarctic Dome Fuji Ice Core (∼100 Years Around 5480 BCE): An Unusual Grand Solar Minimum Occurrence?

“…Therefore, the 36 Cl increase during the 5465−5460 BCE probably reflects the delayed signal of its production increase. Such a delay of 36 Cl increase is similar to the nuclear test 36 Cl data obtained in Vostok (Delmas et al, 2004;Pivot et al, 2019). (Horiuchi et al, 2007(Horiuchi et al, , 2008.…”

“…Here, we should note that possible 36 Cl diffusion might affect our estimation. Evidence of 36 Cl diffusion in low accumulation sites has been obtained from the 36 Cl data in Antarctic Vostok snow around a time period of nuclear bomb tests in the 1950−1960s (Delmas et al., 2004; Pivot et al., 2019). Given the low accumulation rate in the DF (∼2.7 g cm −2 yr −1 water equivalent) (Kawamura et al., 2017), part of the 36 Cl produced around 5469 BCE was possibly moved in the snowpack or lost to the air.…”

“…Here, we should note that possible 36 (Delmas et al, 2004;Pivot et al, 2019). Given the low accumulation rate in the DF (∼2.7 g cm −2 yr −1 water equivalent) (Kawamura et al, 2017), part of the 36 Cl produced around 5469 BCE was possibly moved in the snowpack or lost to the air.…”

The Signal of Solar Storms Embedded in Cosmogenic Radionuclides: Detectability and Uncertainties

“…We extrapolate that this result holds true for 36 Cl that has a similar stratospheric residence time of 1–2 years (Heikkilä, Beer, Feichter, et al., 2009; Synal et al., 1990). Its main difference in comparison to 10 Be concerns its potential for back‐diffusion within the snowpack (Delmas et al., 2004) caused by its gaseous form (H 36 Cl), though this process is not expected to be an important uncertainty for 36 Cl records from localities with sufficiently high accumulation rates (Delmas et al., 2004; Pivot et al., 2019) which is the case in Greenland. Furthermore, we have inferred that a SEP event (or any other cosmic‐ray event) must yield an enhancement in the global annual production rate of 10 Be (and 36 Cl) of at least 4.4σ the GCR‐related baseline for its signature to be identified reliably (at the 3σ level) in annual data in a single ice core record.…”

Global Drivers on Southern Ocean Ecosystems: Changing Physical Environments and Anthropogenic Pressures in an Earth System

“…Heavy metals have been detected in ice core samples, with, for example, lead from Australian mining operations appearing at concentrations of up to 6 pg.g −1 after the start of the industrial revolution (McConell et al, 2014). Radioactive isotopes of elements such as chlorine ( 36 Cl) are, also, still being released from the cryosphere after nuclear bomb tests in the 50's and 60's (Pivot et al, 2019). The persistent organic pollutants (POPs; Krasnobaev et al, 2020) and marine debris, amongst which the plastics have become a focus for policy makers and the public alike (Rochman et al, 2016), will be discussed in detail here.…”