TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 60 (No. 1), pp. 189-203, 2004

Export Production in the Subarctic North Pacific over the Last 800 kyrs: No Evidence for Iron Fertilization?

Stephanie S. Kienast1*, Ingrid L. Hendy2, John Crusius3, Tom F. Pedersen4 and Stephen E. Calvert5

1Woods Hole Oceanographic Institution, Marine Chemistry & Geochemistry, 360 Woods Hole Road, Woods Hole, MA 02543, U.S.A.
2Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1063, U.S.A.
3U.S. Geological Survey, Woods Hole, MA 02543, U.S.A.
4University of Victoria, School of Earth and Ocean Sciences, Victoria, BC, V8P 5C2, Canada
5University of British Columbia, Earth & Ocean Sciences, Vancouver, BC, V6T 1Z4, Canada

(Received 3 September 2003; in revised form 29 November 2003; accepted 1 December 2003)

Abstract: The subarctic North Pacific is a high nitrate-low chlorophyll (HNLC) region, where phytoplankton growth rates, especially those of diatoms, are enhanced when micronutrient Fe is added. Accordingly, it has been suggested that glacial Fe-laden dust might have increased primary production in this region. This paper reviews published palaeoceanographic records of export production over the last 800 kyrs from the open North Pacific (north of ~35°N). We find different patterns of export production change over time in the various domains of the North Pacific (NW and NE subarctic gyres, the marginal seas and the transition zone). However, there is no compelling evidence for an overall increase in productivity during glacials in the subarctic region, challenging the paradigm that dust-born Fe fertilization of this region has contributed to the glacial draw down of atmospheric CO2. Potential reasons for the lack of increased glacial export production include the possibility that Fe-fertilization rapidly drives the ecosystem towards limitation by another nutrient. This effect would have been exacerbated by an even more stable mixed layer compared to today.

*Corresponding author E-mail: skienast@whoi.edu

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