Heterogeneous Reservoirs in the Marine Carbon Cycle

Christopher Follett, Ph.D., 2014
Daniel Rothman, Advisor

This thesis seeks relationship between the distinct reservoirs of organic carbon in the ocean and their underlying complexity. First, we relate the moments of the rate distributions to bulk reservoir properties like average age and flux, specifying them to the lognormal distribution and putting them in the context of age structured models. We apply these ideas to the dissolved organic carbon (DOC) reservoir in the ocean. Using published bulk DOC data and serial oxidation experiments we provide evidence that 30% of the deep ocean DOC reservoir modern and supported by a 1 Pg per year carbon flux, ten times higher than inferred from its bulk radiocarbon age. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Finally, the thesis explores methods for determining the validity of diffusion limitation as the mechanism behind the power-law slowdown in organic remineralization in sediments. We find that diffusion limitation connects the decay behavior of organic material to the correlations found between mineral surface area and organic matter content in sediments.