A sensitivity study of the effect of global change on ocean carbon uptake

Abstract

A two-dimensional global model of ocean chemistry and biology is used to calculate the sensitivity of oceanic CO₂ uptake during the next century to various biological and chemical feedback mechanisms. Model formulations are outlined and the model is validated for current conditions by comparison with data on ¹⁴C and bomb-¹⁴C, primary production, nitrogen, oxygen and DOC. The model includes several mechanisms that are influenced by global change: temperature effects, circulation rate, calcification, UV-damage, eutrophication and CO₂ fertilization. It is concluded that a temperature increase could provide a substantial positive feedback by its effect on ocean chemistry, decreasing carbon uptake by 16%. Biological mechanisms modify oceanic uptake to a relatively minor extent (some 5%) only, implying that abiotic models of anthropogenic CO₂ uptake are expected to give essentially the same answers as models including a biological carbon cycle.