Chlorine 36 fallout in the Summit Greenland ice core project ice core.

Journal of Geophysical Research, Vol. 102, No. C12, p. 26,659-26,662, 1997

S. Baumgartner, J. Beer
Environmental Physics, Swiss Federal Institue for Environmental Science and Technology. Dübendorf, Switzerland
M. Suter, B. Dittrich-Hannen
Institute for Particle Physics, Eidgenössische Technische Hochschule Hönggerberg, Zürich, Switzerland.
H.-A. Synal, P.W. Kubik
Paul Scherrer Institute,Villigen, Switzerland.
C.U. Hammer, H.B. Clausen,
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen..

The natural cosmigenic radioisotope 36Cl has been measured in the Greenland Ice Core Project ice core from Summit, Greenland. Generally, a good correlation between 36Cl and δ18O was found, even in glacial periods with strong δ18O oscillations. The 36Cl flux is calculated assuming an exponential relationship between accumulation rate and δ18O. A prominent excursion is detected between 35 and 40 kyr B.P., which coincides with a similar 10Be peak measured in the same samples. This sheds light on possible causes of the excursion. In the lowest part of the ice core the flux decreses smoothly. This can be interpreted as radioactive decay of 36Cl (T1/2 = 300 kyr).