Export Production in the Subarctic North Pacific over the Last 800 kyrs: No Evidence for Iron Fertilization? |
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Authors: | Stephanie S Kienast Ingrid L Hendy John Crusius Tom F Pedersen Stephen E Calvert |
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Institution: | (1) Woods Hole Oceanographic Institution, Marine Chemistry & Geochemistry, 360 Woods Hole Road, Woods Hole, MA, 02543, U.S.A.;(2) Department of Geological Sciences, University of Michigan, Ann Arbor, MI, 48109-1063, U.S.A;(3) U.S. Geological Survey, Woods Hole, MA, 02543, U.S.A;(4) School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, V8P 5C2, Canada;(5) University of British Columbia, Earth & Ocean Sciences, Vancouver, BC, V6T 1Z4, Canada |
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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.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Atmospheric CO2 HNLC regions glacial-interglacial productivity changes aeolian iron fertilization North Pacific palaeoceanography |
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