The CICS Science group will work together with GFDL through CICS to maintain a group of scientists able to analyze mitigation options as they arise. Over the first 5 years of CMI, we have studied various aspects of two oceanic mitigation options – iron fertilization and deep-sea injection – while providing background knowledge for exploration of general mitigation issues as part of the wedges study of Pacala and Socolow. A further issue that has arisen recently is a resuscitation of the suggestions that global warming might be mitigated by the injection of sulfate aerosols into the atmosphere to reflect sunlight back into space. The tools to investigate this proposal exist at GFDL, and we plan to collaborate with them to better inform ourselves on this option.

While iron fertilization and deep-sea injection do not appear to be gaining traction as viable options, there does continue to be strong interest in them, including amongst private commercial ventures. There are many unresolved questions that are of considerable interest scientifically, and the outcomes will have significant impact on our evaluations of the viability of these options. Two that will be investigated in the near future are:

  1. Sarmiento’s group has carried out a new set of iron fertilization simulations making use of the new generation of ecosystem and iron chemistry models that have been developed over the past decade at Princeton and GFDL. These new fertilization models differ significantly from the major conclusions of our previous research by Gnanadesikan, et al. [2003] in showing a much higher sequestration efficiency. The main reason for this is that the added iron is retained for a long period of time in the models and thus continues to draw carbon down each time it returns to the surface. In previous research, it had been assumed that the added iron would get scavenged very rapidly. The key scientific issue appears to be the extent to which ligands formed primarily by organisms are helping to retain the iron in solution for a long period of time, as the models presently assume. Sarmiento’s group is in the process of investigating these issues, which also have major implications for how we model the response of ocean biology to global warming.
  2. Sarmiento’s group continues to have a strong interest in the scientific underpinnings of the processes that determine the return flow of deep water into the upper ocean. This is of great relevance not only to climate change and oceanic biological productivity, but also to deep sea sequestration of anthropogenic carbon. The recent study by Mignone, et al. [2006] of how Southern Ocean winds and isopycnal mixing together determine the uptake of anthropogenic CO2 by the ocean also has important implications for the escape of CO2 from the deep ocean to the atmosphere in this same region (cf. Mignone, 2004). As a follow on to this research, Sarmiento’s group is initiating a new collaboration with Peter Schlosser of Columbia University that would make use of his observations of helium-3 emanating from mid-ocean ridges in order to further investigate the return pathways of deep water into the surface ocean (see carbon observing system discussion above).