Fixes for a greenhouse planet: Why the jury is still out on Ocean Iron Fertilization (OIF)

Jim Bishop


Purposeful iron addition to high nutrient - low chlorophyll ocean areas (N Pacific; equatorial Pacific; and Southern Ocean) has been proposed as a solar powered way to counter the rapid growth of CO2 in the atmosphere. Recently, there has been a media splash from some commercial ventures wishing to use OIF for both voluntary and formal carbon offset markets. One dozen science based experiments have been conducted internationally since the mid 1990's. Most iron addition experiments led to enhanced phytoplankton growth; however, few have followed the fate of produced organic matter (Did it sink? If not, no effect.). LBNL deployed robotic Carbon Explorers and ship lowered sampling systems south of New Zealand as part of the 2002 Southern Ocean Iron Experiment (Bishop et al. 2004, Science 304, 417-420; Lam and Bishop 2007, Deep-Sea Research II 54 601-638.) and tracked this experiment from beginning to end. We have also investigated the natural iron dynamics of the N Pacific Ocean (Bishop et al., 2002, Science 298, 817-821; Lam et al., 2006, Global Biogeochem. Cycles. 20, GB1006, doi:10.1029/2005GB002557; Lam and Bishop GRL, in press.). Simply stated - no OIF experiment to date has had an a-priori predictable result. Further; the biotic response to naturally and purposefully iron enriched waters has been different. This talk reviews the ocean carbon cycle and the highlights of recent advances of LBNL science and technology aimed at gaining predictability of the substantial biotically mediated carbon flows (50 Pg C/y photosynthetically fixed; 10 Pg C/y exported from the surface layer) in the ocean. For now, the jury is still out on OIF...but we can find out.