Ocean chemistry during glacial time

Measurements of CO₂ to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the CO₂ content of the atmosphere was considerably lower during peak glacial time than during Holocene time. The purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water. Two possible scenarios are presented. One involves alternate storage and erosion of phosphorous leaving residues from shelf sediments. The other involves changes in the $\text{C}\text{P}$ ratio in the organic debris falling to the deep sea. Means of verifying the nutrient cycle hypothesis are also given. It is shown that the ¹³C record as we know it in planktonic and benthic foraminifera, the oxygen record as inferred from benthic foraminifera species distributions, and the early post glacial CaCo₃ preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented. Only if an early post glacial spike in the ¹³C record for planktonic shells could be found would it be possible to eliminate one of these hypotheses (i.e., that involving shelf storage). The implications of these nutrient hypotheses to climate theory are as follows. If shelf storage is responsible for the glacial to interglacial CO₂ increase, then the CO₂ change must be considered an amplifier of some primary cause. The reason is that sea level changes are needed to drive deposition on (and erosion from) the shelves. On the other hand, if changes in the $\text{C}\text{P}$ ratio for falling debris are responsible, then the CO₂ change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle. The latter is possible as self-sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry.