INTERHEMISPHERIC SYNCHRONY OF LATE-GLACIAL CLIMATIC INSTABILITY AS RECORDED IN PROGLACIAL LAKE-MASCARDI, ARGENTINA

Several high-resolution continental records have been reported recentl y in sites in South America, but the extent to which climatic variatio ns were synchronous between the northern and southern hemispheres duri ng the Late-glacial-Holocene transition, and the causes of the climati c changes, remain open questions. Previous investigations indicated th at, east of the Andes, the middle and high latitudes of South America warmed uniformly and rapidly from 13 000 C-14 yr BP, With no indicatio n of subsequent climate fluctuations, equivalent, for example, to the Younger Dryas cooling. Here we present a multiproxy continuous record, radiocarbon dated by accelerated mass spectroscopy, from proglacial L ake Mascardi in Argentina. The results show that unstable climatic con ditions, comparable to those described from records obtained in the No rthern Hemisphere, dominated the Late-glacial-Holocene transition in A rgentina at this latitude. Furthermore, a significant advance of the T ronador ice-cap, which feeds Lake Mascardi, occurred during the Younge r Dryas Chronozone. This instability suggests a step-wise climatic his tory reflecting a global, rather than regional, forcing mechanism. The Lake Mascardi record, therefore, provides strong support for the hypo thesis that ocean-atmosphere interaction, rather than global ocean cir culation alone, governed interhemispheric climate teleconnections duri ng the last deglaciation. (C) 1997 by John Wiley & Sons, Ltd.