Elevated foraminifera-bound nitrogen isotopic composition during the last ice age in the South China Sea and its global and regional implications
| Type | Article | ||||||||
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| Date | 2012-03 | ||||||||
| Language | English | ||||||||
| Author(s) | Ren Haojia1, Sigman Daniel M.2, Chen Min-Te4, Kao Shuh-Ji3 | ||||||||
| Affiliation(s) | 1 : Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. 2 : Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA. 3 : Acad Sinica, Res Ctr Environm Changes, Taipei 115, Taiwan. 4 : Natl Taiwan Ocean Univ, Inst Appl Geophys, Keelung 20224, Taiwan. |
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| Source | Global Biogeochemical Cycles (0886-6236) (Amer Geophysical Union), 2012-03 , Vol. 26 , N. GB1031 , P. 1-13 | ||||||||
| DOI | 10.1029/2010GB004020 | ||||||||
| WOS© Times Cited | 27 | ||||||||
| Note | Auxiliary material for this article contains one text file providing methods, results, and discussions, as well as three figures showing the study site MD97-2142, results of the inter-species difference in foraminifera-bound nitrogen isotopes, and results of the bulk chemical analyses at site MD97-2142. | ||||||||
| Abstract | We report a new foraminifera-bound delta N-15 (FB-delta N-15) record from the South China Sea (SCS) extending back to 42 ka. This record shows a similar to 1.2 parts per thousand glacial-to-interglacial delta N-15 decrease, with a deglacial delta N-15 maximum similar to that observed in many bulk sedimentary delta N-15 records and in a Caribbean FB-delta N-15 record. The glacial-to-interglacial delta N-15 decrease is smaller than in the Caribbean record, indicating that at least half of the Caribbean delta N-15 decrease into the Holocene was regional, not global, supporting the interpretation of a Holocene increase in Atlantic nitrogen fixation. At the same time, the glacial-to-interglacial delta N-15 decrease observed in the SCS may also be explained as a regional signal of increasing nitrogen fixation into the Holocene. Other aspects of the SCS record suggest an effect of physical circulation on FB-delta N-15. FB-delta N-15 starts to increase toward its deglacial maximum before the last ice age ends, and it continues to decrease through the later Holocene, in contrast to the more pure glacial/deglacial/interglacial steps in the Caribbean record. These changes have parallels in other Pacific delta N-15 records, precessionally driven East Asian monsoon records, and the slow Holocene warming of SCS surface waters. In addition, the SCS record exhibits two one-point high-delta N-15 spikes in multiple foraminiferal species that coincide with apparent hydrographic events. Thinning or weakening of the thermocline, in the late glacial and early Holocene as well as during the noted events, may have yielded a higher delta N-15 for thermocline nitrate and thus a higher FB-delta N-15. | ||||||||
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