The last deglaciation in the Southern and Northern Hemispheres: A comparison based on oxygen isotope, sea surface temperature estimates, and accelerator $^{14}$C dating from deep-sea sediments
Résumé
The last deglaciation in two deep-sea sediment cores recovered from the Southern Indian Ocean is studied and compared with two records obtained from the North Atlantic. The chronology has been established by accelerator mass spectrometric (AMS) $^{14}$C dating of planktic foraminifers. Climatic changes are inferred based on $\delta^{18}$0 measurements in planktic foraminifers and on sea surface temperatures (SST) obtained by means of faunal and floral transfer functions. In the North Atlantic, the last deglaciation began at about 15 -14.5 ka, Holocene conditions were reached at about 12.5 - 12.0 ka and a cold interval occurred between 11.0 and 10.0 ka (Younger Dryas Event). In the Southern Ocean, the last degiaciation began between 16.5 and 13.0 ka and Holocene temperatures were reached at about 12.0 ka. Both Southern Ocean records present transitory oscillations: Core MD 84-551 (5SOS) exhibits a temporary increase in $\delta^{18}$0 dated at about 10.5 ka (but it is still unresolved if this feature is due to SST changes or other regional causes) while Core MD 84-527 (44°S) is characterized by a cold event at about 11.6 ka (only in the SST records) and a prominent warm optimum between 10.5 and 8.0 ka (in the SST and $\delta^{18}$0 records). More data are needed to determine if there was a time lag between the last degiaciations in both hemispheres and if common transitory oscillations can be recognized.