Deglacial Atmospheric CO2 Rise Research Articles

Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO 2

Wind-driven upwelling in the ocean around Antarctica helps regulate the exchange of carbon dioxide (CO2) between the deep sea and the atmosphere, as well as the supply of dissolved silicon to the euphotic zone of the Southern Ocean. Diatom productivity south of the Antarctic Polar Front and the subsequent burial of biogenic opal in underlying sediments are limited by this silicon supply. We show that opal burial rates, and thus upwelling, were enhanced during the termination of the last ice age in each sector of the Southern Ocean. In the record with the greatest temporal resolution, we find evidence for two intervals of enhanced upwelling concurrent with the two intervals of rising atmospheric CO2 during deglaciation. These results directly link increased ventilation of deep water to the deglacial rise in atmospheric CO2.

Timing of deglaciation from an oxygen isotope curve for Atlantic deep-sea sediments

The exact timing of deglaciation is an important issue in the context of climatic feedback involving the deglacial rise in atmospheric CO2 seen in ice cores1–4. We have produced evidence, from box cores taken in the equatorial Atlantic, that the last deglaciation occurred in two major steps which were separated by a brief pause5. Here we propose that this pause is equivalent to the period of glacial readvance known as ‘Younger Dryas’, which lasted from about 11 to 10 kyr BP. If our correlation is correct, then the initiation of deglaciation occurred after 14 kyr BP, which disagrees with most other deep-sea timescales.