DID PHYSICAL AND BIOLOGICAL PUMPS CAUSE VARIATIONS IN ATMOSPHERIC pCO₂?

Measurements of CO₂ trapped in the ice of the Antarctic reveal that pCO₂ levels in the atmosphere during glacial periods were ~ 100 ppm less than the pCO₂ levels recorded for interglacial periods before the advent of anthropic activity. Furthermore, studies show a close correlation between atmospheric pCO₂, the volume of ice, and Antarctic temperatures, which suggests that pCO₂ was a forcing or amplifying factor in glacial/interglacial cycles, and highlight the importance of the southern high latitudes in rapid paleoclimatic change. A key element in thermohaline circulation is the return route of deep water masses to the surface via the Antarctic Divergence. This mechanism, known as the “physical pump”, which is partly controlled by the latitudinal position and intensity of the westerly winds, influences the transfer of heat and carbon from the deep ocean reservoir to the ocean surface and the atmosphere, and has an impact at a global scale. Furthermore, in addition to this physical pump, there is also a “biological pump”, which corresponds to the transfer of particulate carbon (organic and inorganic) from the surface of the ocean to the deep ocean via the activity of primary producers and calcareous plankton respectively, which might explain a significant proportion of the changes in atmospheric pCO₂ during the last deglaciations. However, up until now few studies have focused on the coupled action of physical and biological pumps in the past.