North Pacific-wide spreading of isotopically heavy nitrogen from intensified denitrification during the Bølling/Allerød and post-younger dryas periods: evidence from the Western Pacific

Kao, Shuh Ji; Liu, K. K.; Hsu, Shih-Chieh; Chang, Yuan‐Pin; Dai, Minhan

doi:10.5194/bgd-5-1017-2008

Cited by 2 publications

(3 citation statements)

References 41 publications

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“…Moreover, downcore records exhibiting the changes in δ 15 N associated with denitrification are not restricted to regions of active water column denitrification. Advection in the subsurface carries the isotopic signal as far as the Subantarctic Front in the SE Pacific [ Martinez et al , 2006], Oregon and British Columbia in the NE Pacific [ Kienast et al , 2002], the subarctic North Pacific [ Galbraith et al , 2008], and the Okinawa Trough [ Kao et al , 2008] and the Indonesian Throughflow [ Kienast et al , 2008] in the western Pacific. The pattern in margin sedimentary δ 15 N records, with glacial periods bearing lower δ 15 N relative to interglacial periods, fits with what is observed in the EEP records (Figures 3g).…”

Section: Discussionmentioning

confidence: 99%

“…In the EEP, the low oxygen tongue coming offshore Peru is apparently a significant source of nitrate to the Equatorial upwelling system. The long distance advection of these low oxygen, high δ 15 N nitrate water masses is likely the origin of the signal in the far Western Pacific as well [ Kao et al , 2008]. The fit is not perfect between the EEP and the margin record or even between the various marginal records because each locality witnesses both the large scale changes in denitrification as well as local influences including but not limited to variations in the amount or δ 15 N of source nitrate, changes in relative utilization, and possibly local nitrogen fixation and/or diagenesis.…”

Section: Discussionmentioning

confidence: 99%

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Nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial Pacific

et al. 2009

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[1] The Eastern Equatorial Pacific (EEP) is a high nutrient-low chlorophyll region of the ocean. Downcore nitrogen isotope records from the EEP have been previously interpreted as a direct reflection of changes in nutrient consumption. However, the observed changes in sedimentary d 15 N since the last glacial maximum have no coherent relationship with export productivity or an inferred variation in the iron-to-nitrate ratio of the surface waters. Rather, downcore N isotope records in the EEP strongly resemble changes in the extent of water column denitrification as recorded in nearby sedimentary d 15 N records along the western margin of the Americas. This similarity is attributed to the overprinting of the N isotopic composition of nitrate in the EEP through the advection of nitrate westward from the margins in the subsurface. A local nitrogen isotope record of changes in the degree of nutrient consumption is extracted from the bulk sedimentary record by subtracting two different sedimentary d15 N records of denitrification changes from two new EEP d 15N records (TR163-22 and ODP Site 1240). The denitrification records used are from 1) the Central American margin (ODP Site 1242) and 2) the South American margin (GeoB7139-2). The degree of consumption in the surface waters declines rapidly from elevated values during the last glacial maximum to a pair of minima around 15 and 11-13 ka, and finally it increases into the Holocene. The derived EEP nitrogen isotope record indicates that the regional peak in export productivity occurred when the supply of nutrients exceeded the apparently high demand. The influx of nutrients during the deglaciation is attributed to the resumption of intense overturning in the Southern Ocean and the release of sequestered CO 2 and nutrient-rich, O 2 poor waters from the deep ocean. This has important implications for understanding the glacial-interglacial scale variation in intermediate water suboxia and water column denitrification.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial Pacific

et al. 2009

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“…If we take depth as a robust proxy for the controls on alteration and consider significant changes in burial depth at a given site unlikely on orbital timescales or without major changes in the site location (e.g., tectonic transport away from a spreading ridge), then significant temporal changes in the degree of alteration at a given site are unlikely as well. Furthermore, regionally coherent downcore records of δ 15 N changes, across a range of sedimentation rates and sediment compositions, from the continental margin to the central/western Equatorial Pacific argue against significant changes in preservation as a function of realistic changes in accumulation rates at a single site [ Galbraith et al , 2008a; Kao et al , 2008; Martinez et al , 2006]. The data suggest that spatial comparisons using absolute δ 15 N values should consider the potential impact of alteration at deeper/more distal sites.…”

Section: Sediment Trap and Surface Sediment Compilationmentioning

confidence: 99%

A review of nitrogen isotopic alteration in marine sediments

et al. 2012

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[1] Nitrogen isotopes are an important tool for evaluating past biogeochemical cycling from the paleoceanographic record. However, bulk sedimentary nitrogen isotope ratios, which can be determined routinely and at minimal cost, may be altered during burial and early sedimentary diagenesis, particularly outside of continental margin settings. The causes and detailed mechanisms of isotopic alteration are still under investigation. Case studies of the Mediterranean and South China Seas underscore the complexities of investigating isotopic alteration. In an effort to evaluate the evidence for alteration of the sedimentary N isotopic signal and try to quantify the net effect, we have compiled and compared data demonstrating alteration from the published literature. A >100 point comparison of sediment trap and surface sedimentary nitrogen isotope values demonstrates that, at sites located off of the continental margins, an increase in sediment 15 N/ 14 N occurs during early burial, likely at the seafloor. The extent of isotopic alteration appears to be a function of water depth. Depth-related differences in oxygen exposure time at the seafloor are likely the dominant control on the extent of N isotopic alteration. Moreover, the compiled data suggest that the degree of alteration is likely to be uniform through time at most sites so that bulk sedimentary isotope records likely provide a good means for evaluating relative changes in the global N cycle.Citation: Robinson, R. S., et al. (2012), A review of nitrogen isotopic alteration in marine sediments, Paleoceanography, 27, PA4203,

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North Pacific-wide spreading of isotopically heavy nitrogen from intensified denitrification during the Bølling/Allerød and post-younger dryas periods: evidence from the Western Pacific

Cited by 2 publications

References 41 publications

Nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial Pacific

Nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial Pacific

A review of nitrogen isotopic alteration in marine sediments

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