New Directions: Enhancing the natural sulfur cycle to slow global warming

摘要

Full scale ocean iron fertilization of the Southern Ocean (SO) has been proposed previously as a means to help mitigate rising CO_2 in the atmosphere (Martin et al, 1990, Nature 345, 156-158). Here we describe a different, more leveraged approach to partially regulate climate using limited iron enhancement to stimulate the natural sulfur cycle, resulting in increased cloud reflectivity that could cool large regions of our planet. Some regions of the Earth's oceans are high in nutrients but low in primary productivity. The largest such region is the SO followed by the equatorial Pacific. Several mesoscale (10~2km~2) experiments have shown that the limiting nutrient to productivity is iron. Yet, the effectiveness of iron fertilization for sequestering significant amounts of atmospheric CO_2 is still in question. However, marine microorganisms not only consume inorganic carbon but also produce and consume many climate relevant organic gases. The greatest climate effect of iron fertilization may be in enhancing dimethyl sulfide (DMS) production, leading to changes in the optical properties of the atmosphere and cooling of the region.