Unchanged nitrogen isotopic composition of organic matter in the South China Sea during the last climatic cycle: Global implications

Kienast, Markus

doi:10.1029/1999pa000407

Cited by 112 publications

(102 citation statements)

References 90 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The range of δ 15 N values in the two cores examined by us is similar to those observed in 17940-2 (Kienast, 2000) and 1144 (Higginson et al, 2003) from the northern SCS (see Fig. 1b for locations).…”

Section: δ 15 N Records In the South China Seasupporting

confidence: 64%

“…Except the transgression, no distinctive shift in sedimentary δ 15 N has been found between glacial and interglacial periods. Thus, it would be reasonable to conclude that the isotopic composition of nitrate in the upper ocean was the same during the two climate states as suggested by Kienast (2000). On the other hand, it is conceivable that the nitrate reservoir in the upper water column had an elevated mean δ 15 N value during these warm periods reflecting a decrease in the nitrogen inventory during the transgression period.…”

Section: Discussionmentioning

confidence: 77%

“…Evidence from the South China Sea (SCS), a cul-de-sac (Fig. 1a) of North Pacific Intermediate Water (NPIW) (You et al, 2005), believed to be well-suited to determine the extent of basin-wide influence of WCD in the Eastern Tropical North Pacific (ETNP), shows insignificant responses in sedimentary δ 15 N during the last deglaciation when WCD peaked in the ETNP (Kienast, 2000;Higginson et al, 2003). However, in order to adequately assess the effect of intensified WCD on marine N inventory during the last deglaciation more sedimentary δ 15 N records are needed from oligotrophic regions of the ocean, particularly the western Pacific.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

et al. 2008

View full text Add to dashboard Cite

Abstract. Sedimentary δ 15 N records in two IMAGES cores (MD012404 and MD012403) retrieved from the Okinawa Trough (OT) in the western North Pacific reveal deglacial increases with two peaks occurring during the Bølling/Allerød and the Preboreal/early Holocene periods. These peaks are synchronous with previously reported δ 15 N peaks in the Eastern Tropical North Pacific, although the amplitudes (from 3.8 to 5.8‰) are much smaller in the OT. Similar δ 15 N values for the last glacial maximum and the late-Holocene observed by us at a site far from the present-day zones of water-column denitrification (WCD) indicate that the mean 15 N/ 14 N of nitrate in the upper ocean did not differ much between the two climate states. The accumulation rate of organic carbon and total sulfur content are used as indices of the local WCD potential. The results suggest that enhancement of global WCD rather than local denitrification should be responsible for the deglacial maxima of sedimentary δ 15 N in the Okinawa Trough. Our data could provide additional constraints to better understand changes in nitrogen budget during the glacial to interglacial transition.

show abstract

Section: δ 15 N Records In the South China Seasupporting

confidence: 64%

Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

et al. 2008

View full text Add to dashboard Cite

show abstract

“…We use endmember d 15 N values for these components of 0& (Ozima and Podosek, 2002), À5 ± 2& (Marty, 1995;Cartigny et al, 1998;Sano et al, 1998;Marty and Zimmermann, 1999;Sano et al, 2001), and +7 ± 4& (Peters et al, 1978;Bebout and Fogel, 1992;Boyd and Pillinger, 1994;Bebout, 1995;Kienast, 2000;Sadofsky and Bebout, 2004;Li and Bebout, 2005) for atmosphere, upper mantle, and subducted hemipelagic sediments, respectively. An additional potential contributor of nitrogen to arc gases is the subducted altered oceanic crust; its d 15 N value, however, is currently poorly constrained but may be as low as À2.9& (Li et al, 2003).…”

Section: Gas Provenance: Resolution Into Endmembersmentioning

confidence: 99%

Tracing nitrogen in volcanic and geothermal volatiles from the Nicaraguan volcanic front

Elkins

Fischer

Hilton

et al. 2006

Geochimica et Cosmochimica Acta

114

View full text Add to dashboard Cite

We report new chemical and isotopic data from 26 volcanic and geothermal gases, vapor condensates, and thermal water samples, collected along the Nicaraguan volcanic front. The samples were analyzed for chemical abundances and stable isotope compositions, with a focus on nitrogen abundances and isotope ratios. These data are used to evaluate samples for volatile contributions from magma, air, air-saturated water, and the crust. Samples devoid of crustal contamination (based upon He isotope composition) but slightly contaminated by air or air-saturated water are corrected using N 2 /Ar ratios in order to obtain primary magmatic values, composed of contributions from upper mantle and subducted hemipelagic sediment on the down-going plate. Using a mantle endmember with d 15 N = À5& and N 2 /He = 100 and a subducted sediment component with d 15 N = +7& and N 2 /He = 10,500, the average sediment contribution to Nicaraguan volcanic and geothermal gases was determined to be 71%. Most of the gases were dominated by sediment-derived nitrogen, but gas from Volcán Mombacho, the southernmost sampling location, had a mantle signature (46% from subducted sediment, or 54% from the mantle) and an affinity with mantle-dominated gases discharging from Costa Rica localities to the south. High CO 2 /N 2 exc. ratios (N 2 exc. is the N 2 abundance corrected for contributions from air) in the south are similar to those in Costa Rica, and reflect the predominant mantle wedge input, whereas low ratios in the north indicate contribution by altered oceanic crust and/or preferential release of nitrogen over carbon from the subducting slab. Sediment-derived nitrogen fluxes at the Nicaraguan volcanic front, estimated by three methods, are 7.8 · 10 8 mol N/a from 3 He flux, 6.9 · 10 8 mol/a from SO 2 flux, and 2.1 · 10 8 and 1.3 · 10 9 mol/a from CO 2 fluxes calculated from 3 He and SO 2 , respectively. These flux results are higher than previous estimates for Central America, reflecting the high sediment-derived volatile contribution and the high nitrogen content of geothermal and volcanic gases in Nicaragua. The fluxes are also similar to but higher than estimated hemipelagic nitrogen inputs at the trench, suggesting addition of N from altered oceanic basement is needed to satisfy these flux estimates. The similarity of the calculated input of N via the trench to our calculated outputs suggests that little or none of the subducted nitrogen is being recycled into the deeper mantle, and that it is, instead, returned to the surface via arc volcanism.

show abstract

“…Attempts have been made to reconstruct the average δ 15 N of marine N and a number of theoretical studies point to this parameter as reflecting the balance between the largest N flux terms (Brandes and Devol, 2002). Due to good organic matter preservation and a location remote from high-nutrient, low chlorophyll (HNLC) and denitrification regions, sediment records for δ 15 N from the South China Sea have been cited as evidence for little change in ocean average δ 15 N over the last glacial cycle (Kienast, 2000). This has led to the conclusion that either N 2 fixation changes compensated for any change in denitrification and/or there was no change in the proportioning of denitrification between the sediment and the water column (Brandes and Devol, 2002).…”

mentioning

confidence: 99%

Constraints on oceanic N balance/imbalance from sedimentary <sup>15</sup>N records

Altabet

2007

Biogeosciences

115

View full text Add to dashboard Cite

Abstract. According to current best estimates, the modern ocean's N cycle is in severe deficit. N isotope budgeting provides an independent geochemical constraint in this regard as well as the only means for past reconstruction. Overall, it is the relative proportion of N 2 fixation consumed by water column denitrification that sets average oceanic δ 15 N under steady-state conditions. Several factors (conversion of organic N to N 2 , Rayleigh closed and open system effects) likely reduce the effective fractionation factor (ε) for water column denitrification to about half the inherent microbial value for ε den . If so, the average oceanic δ 15 N of ∼5‰ is consistent with a canonical contribution from water column denitrification of 50% of the source flux from N 2 fixation. If an imbalance in oceanic N sources and sinks changes this proportion then a transient in average oceanic δ 15 N would occur. Using a simple model, changing water column denitrification by ±30% or N 2 fixation by ±15% produces detectable (>1‰) changes in average oceanic δ 15 N over one residence time period or more with corresponding changes in oceanic N inventory. Changing sedimentary denitrification produces no change in δ 15 N but does change N inventory. Sediment δ 15 N records from sites thought to be sensitive to oceanic average δ 15 N all show no detectible change over the last 3 kyr or so implying a balanced marine N budget over the latest Holocene. A mismatch in time scales is the most likely meaningful interpretation of the apparent conflict with modern flux estimates. Decadal to centennial scale oscillations between net N deficit and net surplus may occur but on the N residence timescale of several thousand years, net balance is achieved in sum. However, sediment δ 15 N records from the literature covering the period since the last glacial maximum show excursions of up to several ‰ that are consistent with sustained N deficit during the deglaciation followed by readjustment and establishment of balance in the early Holocene.Correspondence to: M. A. Altabet (maltabet@umassd.edu) Since imbalance was sustained for one N residence time period or longer, excursions in ocean N inventory of 10 to 30% likely occurred. The climatic and oceanographic changes that occurred over this period evidently overcame, for a time, the capacity of ocean biogeochemistry to maintain N balance.

show abstract

Unchanged nitrogen isotopic composition of organic matter in the South China Sea during the last climatic cycle: Global implications

Cited by 112 publications

References 90 publications

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

Tracing nitrogen in volcanic and geothermal volatiles from the Nicaraguan volcanic front

Constraints on oceanic N balance/imbalance from sedimentary <sup>15</sup>N records

Contact Info

Product

Resources

About

Unchanged nitrogen isotopic composition of organic matter in the South China Sea during the last climatic cycle: Global implications

Cited by 112 publications

References 90 publications

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

Tracing nitrogen in volcanic and geothermal volatiles from the Nicaraguan volcanic front

Constraints on oceanic N balance/imbalance from sedimentary &lt;sup&gt;15&lt;/sup&gt;N records

Contact Info

Product

Resources

About

Constraints on oceanic N balance/imbalance from sedimentary <sup>15</sup>N records