Glacial CO2 sequestration

Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Abstract Given the magnitude and dynamism of the deep marine carbon reservoir, it is almost certain that past glacial – interglacial fluctuations in atmospheric CO 2 have relied at least in part on changes in the carbon storage capacity of the deep sea. To date, physical ocean circulation mechanisms that have been proposed as viable explana-5 tions for glacial – interglacial CO 2 change have focussed almost exclusively on dynam-ical or kinetic processes. Here, a simple mechanism is proposed for increasing the carbon storage capacity of the deep sea that operates via changes in the volume of southern-sourced deep-water filling the ocean basins, as dictated by the hypsometry of the ocean floor. It is proposed that a water-mass that occupies more than the bottom 10 3 km of the ocean will essentially determine the carbon content of the marine reservoir. Hence by filling this interval with southern-sourced deep-water (enriched in dissolved CO 2 due to its particular mode of formation) the amount of carbon sequestered in the deep sea may be greatly increased. A simple box-model is used to test this hypothesis, and to investigate its implications. It is suggested that up to 70% of the observed glacial 15 – interglacial CO 2 change might be explained by the replacement of northern-sourced deep-water below 2.5 km water depth by its southern counterpart. Most importantly, it is found that an increase in the volume of southern-sourced deep-water allows glacial CO 2 levels to be simulated easily with only modest changes in Southern Ocean biological export or overturning. If incorporated into the list of contributing factors to marine 20 carbon sequestration, this mechanism may help to significantly reduce the " deficit " of explained glacial – interglacial CO 2 change. 1 Explaining glacial – interglacial CO 2 change Although it is clear that changes in atmospheric CO 2 have remained tightly coupled with global climate change throughout the past ∼730 000 years (Siegenthaler et al., Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU mystery. The magnitude of the marine carbon reservoir, and its inevitable response to changes in atmospheric CO 2 (Broecker, 1982a), guarantees a significant role for the ocean in glacial – interglacial CO 2 change. Based on thermodynamic …