Wintertime phytoplankton bloom in the subarctic Pacific supported by continental margin iron
Figure S1: FeKa maps through data analysis steps for a representative sample (96006p, OSP, 71m) mapped in July 2003. (103.5Kb)
Figure S2: Ti XRF map of SOFeX mesh blank showing Ti threshold (10th percentile) in white, outlining the “hole” regions. (198.6Kb)
Figure S4: Determination of Fe noise function using sample Jul96006p (OSP, 71m) and Cr as a noise diagnostic. (88.48Kb)
Lam, Phoebe J.
Bishop, James K. B.
Henning, Cara C.
Marcus, Matthew A.
Waychunas, Glenn A.
Fung, Inez Y.
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Heightened biological activity was observed in February 1996 in the high-nutrient low-chlorophyll (HNLC) subarctic North Pacific Ocean, a region that is thought to be iron-limited. Here we provide evidence supporting the hypothesis that Ocean Station Papa (OSP) in the subarctic Pacific received a lateral supply of particulate iron from the continental margin off the Aleutian Islands in the winter, coincident with the observed biological bloom. Synchrotron X-ray analysis was used to describe the physical form, chemistry, and depth distributions of iron in size fractionated particulate matter samples. The analysis reveals that discrete micron-sized iron-rich hot spots are ubiquitous in the upper 200 m at OSP, more than 900 km from the closest coast. The specifics of the chemistry and depth profiles of the Fe hot spots trace them to the continental margins. We thus hypothesize that iron hot spots are a marker for the delivery of iron from the continental margin. We confirm the delivery of continental margin iron to the open ocean using an ocean general circulation model with an iron-like tracer source at the continental margin. We suggest that iron from the continental margin stimulated a wintertime phytoplankton bloom, partially relieving the HNLC condition.
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 20 (2006): GB1006, doi:10.1029/2005GB002557.