Monsoonal influence on Southern Hemisphere 14CO2

Abstract

Annual rings of a cross-dated teak tree core from Muna Island, Sulawesi, Indonesia in the southern equatorial tropics were analysed for radiocarbon from 1951-1979. 14C levels at Muna started rising in 1956 and reached a maximum value of 667‰ in early 1965. The Muna 14C levels are significantly higher than those derived from the other Southern Hemisphere (SH) 14C records (including tree rings and atmospheric CO2 sampling) for 1959 and 1963-1965. During the growing season of teak tree rings at this location (Nov-Apr) the Inter-tropical Convergence Zone (ITCZ) moves southward of Muna. Our results indicate that the island is strongly influenced by Northern Hemisphere (NH) air masses carried by the winter Asian monsoon, while the other more southerly SH sites remain covered by SH air masses. This monsoonal effect on atmospheric 14C at Muna is evident during the periods of rapidly rising atmospheric 14C (1959 and 1963-1965), when there is an enhanced 14C contrast between northern and southern air masses. © 2012. American Geophysical Union. All Rights Reserved.