Mesoscale Iron Enrichment Experiments 1993-2005: Synthesis and Future Directions

P. W. Boyd, T. Jickells, C. S. Law, S. Blain, E. A. Boyle, K. O. Buesseler,K. H. Coale, J. J. Cullen, H. J. W. de Baar, M. Follows, M. Harvey,

C. Lancelot, M. Levasseur, N. P. J. Owens, R. Pollard, R. B. Rivkin,J. Sarmiento, V. Schoemann, V. Smetacek, S. Takeda, A. Tsuda,

S. Turner, A. J. Watson

History

• Several Important Papers, 1990-91:– Glacial-Interglacial CO2 Change: the Iron Hypothesis– The Case For Iron

• Hypothesis:– “phytoplankton growth in major nutrient-rich waters is

limited by iron deficiency”• Testing:

– Early small scale testing & shipboard work uncertain– Mesoscale experiments suggested

Mesoscale Iron Addition Experiments

• Questions?– Will Fe increase Primary Production in HNLC

areas?– Subsequent affect on Nutrient use?– On export?

• 12 FeAX’s– HNLC locations (See Figure 1)– Common experimental framework for comparison

Published by AAAS

P. W. Boyd et al., Science 315, 612 -617 (2007)

Fig. 1. Annual surface mixed-layer nitrate concentrations in units of {micro}mol liter-1 (48), with approximate site locations of FeAXs (white crosses), FeNXs (red crosses), and a joint Fe and P

enrichment study of the subtropical LNLC Atlantic Ocean (FeeP; green cross)

Published by AAAS

P. W. Boyd et al., Science 315, 612 -617 (2007)

Fig. 2. A comparison for Southern Ocean waters of mechanisms responsible for perturbations in Fe supply

Published by AAAS

P. W. Boyd et al., Science 315, 612 -617 (2007)

Fig. 3. Summary of published Fe/C molar ratios (on a log scale) from (A) low-Fe HNLC waters and (B) high-Fe waters and FeAXs (FeAXs denoted by hatched bars)