Consistent relationship between global climate and surface nitrate utilization in the western subarctic Pacific throughout the last 500 ka
| Type | Article | ||||||||
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| Date | 2008-05 | ||||||||
| Language | English | ||||||||
| Author(s) | Galbraith Eric D.1, 6, Kienast Markus4, Jaccard Samuel L.2, Pedersen Thomas F.5, Brunelle Brigitte G.1, Sigman Daniel M.1, Kiefer Thorsten3 | ||||||||
| Affiliation(s) | 1 : Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA. 2 : ETH, Dept Earth Sci, Inst Geol, CH-8092 Zurich, Switzerland. 3 : Past Global Changes Int Project Off, CH-3007 Bern, Switzerland. 4 : Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. 5 : Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC V8W 3P6, Canada. 6 : Univ British Columbia, Dept Earth & Ocean Sci, Vancouver, BC V5Z 1M9, Canada. |
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| Source | Paleoceanography (0883-8305) (Amer Geophysical Union), 2008-05 , Vol. 23 , N. 2 / PA2212 , P. 1-11 | ||||||||
| DOI | 10.1029/2007PA001518 | ||||||||
| WOS© Times Cited | 74 | ||||||||
| Abstract | [1] The open subarctic Pacific is, at present, a high nitrate low chlorophyll (HNLC) region, where nitrate is perennially abundant at the surface. Theoretically, the HNLC status of this region is subject to modification by ocean circulation and/or micronutrient supply, with implications for the effectiveness of the biological pump and hence carbon sequestration in the ocean interior. Records of biogenic detritus in sediments from throughout the subarctic Pacific indicate that export production was generally lower during glacial maxima, while nitrogen isotope measurements from the Bering Sea have shown that nitrate consumption there was more complete during the last glacial period than it is today. Here, nitrogen isotopic analyses of bulk sediments (delta N-15(bulk)) from three deep water sites in the open subarctic Pacific are evaluated in terms of regional nitrate isotopic composition and local relative nitrate utilization. The eastern subarctic Pacific delta N-15(bulk) record bears great similarity to delta N-15(bulk) records from the western margin of North America over the last glacial cycle, suggesting that variability in the isotopic composition of subeuphotic zone nitrate, the growth substrate, is reasonably coherent throughout the northeast Pacific and dominates at these sites. However, the two western subarctic Pacific records, which lie at the heart of the HNLC region, display a different pattern, implying that significant changes in local relative nitrate utilization overlie the regional background variability. After a novel correction intended to remove the background signal associated with denitrification in the eastern tropical North Pacific, these nitrate utilization records are correlated with a benthic oxygen isotope stack reflecting global deep ocean temperature and ice volume (r(2) = 0.65). The correlation implies a strong link between global climate and subarctic Pacific nitrate utilization, with nearly complete nitrate consumption during glacial periods when export production was low. | ||||||||
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