INTERHEMISPHERIC SYNCHRONY OF THE LAST DEGLACIATION INFERRED FROM ALKENONE PALAEOTHERMOMETRY

The relative timings of the last deglacial warming in the Southern and Northern hemispheres are not well constrained, but are a crucial comp onent in understanding the mechanisms of deglaciation(1). A clearer pi cture of the degree of interhemispheric synchrony has been obscured by a dearth of high-resolution temperature records that can be tied to t he absolute calendar timescale. Moreover, the quantification of tropic al temperatures during the last glacial cycle is controversial(2-8). H ere we apply the alkenone method of sea surface temperature reconstruc tion(9,10) to several high-resolution sediment cores recovered from th e tropical Indian Ocean between 20 degrees N and 20 degrees S. The inf erred initial sea surface temperature warming similar to 15,000 calend ar years ago at 20 degrees S is in phase with Northern Hemisphere sea (this study) and air(11) temperature changes, but lags Antarctic warmi ng(12-14) by several millennia. This finding, along with the results o f recent modelling studies(15,16), provides strong support for the ide a that changes in the ocean's global thermohaline circulation were not the only cause of interhemispheric climate teleconnection during the last deglaciation.