Bishop, James K.B., and Todd J. Wood

EO Lawrence Berkeley National Laboratory, Tel: 510-495-2457, Fax: 510-486 5686, E-mail: JKBishop@lbl.gov

Robotic assessment of natural and purposeful iron fertilization of the ocean: Asian dust and SOFeX

Carbon biomass in the ocean turns over once per week. Consequently, there is a major observational gap preventing the comprehensive understanding of how the ocean's biological carbon pump contributes to the regulation of atmospheric CO₂ and how this will change in the future. This gap can be overcome by using autonomous profiling robots.

The first two Carbon Explorers (telemetry enhanced and remotely controlled ARGO floats) were launched in April 2001 near Station PAPA (50N 145W) and recorded a carbon biomass doubling following deposition of iron-rich Gobi Desert dust (Bishop et al. 2002). Another four Carbon Explorers were deployed southeast of New Zealand in January 2002 at 55S and 66S near 172W during the Southern Ocean (iron) Fertilization Experient (SOFEX).

The SOFeX Explorers at 55S deployed 'in' and 'out' of the iron-amended waters followed the experiment for nearly two months with dawn, noon, and dusk profiles of carbon biomass, T and S from the surface to 1000 m in the mesopelagic zone. In between profiles, the floats followed the systematics of carbon sedimentation at 100 m. Real time data sent to shore documented a 4-5 times enhancement carbon biomass in near surface waters and a subsequent enhancement of carbon sedimentation below 100m. The Explorer at 66S followed the effects of iron enrichment but also recored natural carbon biomass variability within the "ice covered" seasonal ice zone ice from May through November 2002. SOFeX Carbon Explorers are still relaying data in real time on carbon biomass variability one year after deployment.