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

Cl-36 production in the atmosphere is modulated by the magnetic field intensity of both the Sun and the Earth. The record of Cl-36 concentration along with that of Be-10 in ice cores may therefore provide information as to their variability. To better understand the Cl-36 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 Cl-36, which was injected into the stratosphere and spread around the globe. In the late 1950s this anthropogenic pulse led to an increase of Cl-36 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 Cl-36 today. This pollution results from gaseous (HCl)-Cl-36 mobility at low accumulation sites and implies re-emission of Cl-36 from the snowpack that is not observed at Talos Dome. The Cl-36/Cl- ratio may be used to discriminate the stratospheric anthropogenic Cl-36 source from the tropospheric natural Cl-36 source, which allows us to discuss the immobile vs. mobile Cl-36 in the Vostok snowpack.