國立虎尾科技大學 |

Use of the nitrate isotopes in the ocean interior to explore the isotopic composition of sinking nitrogen and its implications for marine biogeochemical cycles.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Use of the nitrate isotopes in the ocean interior to explore the isotopic composition of sinking nitrogen and its implications for marine biogeochemical cycles./
Author:	Marconi, Dario.
Description:	1 online resource (319 pages)
Notes:	Source: Dissertation Abstracts International, Volume: 78-11(E), Section: B.
Subject:	Biological oceanography. -
Online resource:	click for full text (PQDT)
ISBN:	9780355041491

Use of the nitrate isotopes in the ocean interior to explore the isotopic composition of sinking nitrogen and its implications for marine biogeochemical cycles.
Marconi, Dario.

Use of the nitrate isotopes in the ocean interior to explore the isotopic composition of sinking nitrogen and its implications for marine biogeochemical cycles. - 1 online resource (319 pages)

Source: Dissertation Abstracts International, Volume: 78-11(E), Section: B.

Thesis (Ph.D.)--Princeton University, 2017.

Includes bibliographical references

This thesis uses measurements and models of the 15N/14N and 18O/16O (delta15N and delta18O) of nitrate (NO3-) to gain new constraints on the delta15N of sinking nitrogen that derives from the photosynthetically active surface layer and is remineralized in the ocean interior. The delta15N of sinking nitrogen, in turn, reflects important biogeochemical processes in the ocean. For example, it can reveal (1) the spatial distribution of N2 fixation, the dominant source of biologically available nitrogen ("fixed N") to the ocean and (2) the transport of nitrate from high to low latitude regions and its subsequent processing. Moreover, better information regarding the delta15N of sinking N would significantly improve our ability to simulate denitrification, the dominant loss mechanism for oceanic fixed N.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355041491Subjects--Topical Terms:

1178855
Biological oceanography.
Index Terms--Genre/Form:

554714
Electronic books.

Use of the nitrate isotopes in the ocean interior to explore the isotopic composition of sinking nitrogen and its implications for marine biogeochemical cycles.
LDR:05280ntm a2200385K 4500 001 913257
005 20180618102556.5
006 m o u
007 cr mn||||a|a||
008 190606s2017 xx obm 000 0 eng d
020 $a 9780355041491
035 $a (MiAaPQ)AAI10284265
035 $a (MiAaPQ)princeton:12170
035 $a AAI10284265
040 $a MiAaPQ $b eng $c MiAaPQ
100 1 $a Marconi, Dario. $3 1186012
245 1 0 $a Use of the nitrate isotopes in the ocean interior to explore the isotopic composition of sinking nitrogen and its implications for marine biogeochemical cycles.
264 0 $c 2017
300 $a 1 online resource (319 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertation Abstracts International, Volume: 78-11(E), Section: B.
500 $a Adviser: Daniel M. Sigman.
502 $a Thesis (Ph.D.)--Princeton University, 2017.
504 $a Includes bibliographical references
520 $a This thesis uses measurements and models of the 15N/14N and 18O/16O (delta15N and delta18O) of nitrate (NO3-) to gain new constraints on the delta15N of sinking nitrogen that derives from the photosynthetically active surface layer and is remineralized in the ocean interior. The delta15N of sinking nitrogen, in turn, reflects important biogeochemical processes in the ocean. For example, it can reveal (1) the spatial distribution of N2 fixation, the dominant source of biologically available nitrogen ("fixed N") to the ocean and (2) the transport of nitrate from high to low latitude regions and its subsequent processing. Moreover, better information regarding the delta15N of sinking N would significantly improve our ability to simulate denitrification, the dominant loss mechanism for oceanic fixed N.
520 $a The fixed N budget is central in the debate regarding the degree to which interactions among ocean organisms stabilize the ocean's biogeochemical cycles, with implications for the variability of global biological fertility and of CO2 and O2 concentrations in the atmosphere. The system of nitrogen isotopes can constrain the fixed N budget, but this requires a robust estimate for the isotope effect of water column denitrification (epsilonwcd). N isotope budgeting using an epsilonwcd of ~25‰ (inferred from treating observations from ocean suboxic zones with the Rayleigh model) result in a global denitrification rate that is much higher than the global rate of N2 fixation and thus an ocean N budget far in deficit. Recent culture experiments indicate that epsilonwcd may be much lower (13‰). In the context of the isotope budgeting, this value would imply a lower global rate of denitrification and a roughly balanced fixed N budget. Chapter 2 explores the case for a lower epsilonwcd using a multi-box model framework under various assumptions regarding the routes of nitrate-bearing water transport from the high latitude regions to the denitrification zones and the delta15N of the sinking N that adds nitrate to this water during its transport to these zones. The analysis shows that, assuming a plausible delta15N range for sinking N in the low latitudes, denitrification zone observations can be reproduced with a low isotope effect of ~13‰. Further, the estimates supporting the canonical epsilonwcd of ~25‰ may be an artifact of the inaccurate assumption that the regeneration of sinking N is a minor influence on the nitrate isotope distributions near denitrification zones.
520 $a Chapter 3 investigates the impact of the subduction of high latitude surface waters (SAMW) with high-delta15N (~6.2‰) and high-delta18O (~3.5‰) nitrate on the delta15N of nitrate supply to North Atlantic euphotic zone (from ~20°N to ~40°N). Nitrate isotope measurements along the zonal US GTUS transect indicate that the nitrate delta15N of SAMW- derived waters is up to ~0.6‰ higher than the delta15N of deep nitrate (~4.8‰) while the delta18O is not similarly elevated. Its low delta18O reflects that nitrate at shallow and mid-depths is mostly regenerated, masking the high delta18O of preformed nitrate from the Southern Ocean.
520 $a Chapter 4 reports and interprets nitrate isotope data along the CLIVAR A16N, a hydrographic section from south of Iceland to 6°S in the tropical Atlantic that provides a meridional view that is closely related to the largely north/south subsurface circulation of the Atlantic. Three approaches are used to calculate the delta15N of regenerated nitrate and of sinking N.
520 $a Chapter 5 uses nitrate delta15N measurements along different transects of the Atlantic (including A16N and US GTUS) to pursue the question of the controls on the rate of N2 fixation in the Atlantic basin. A novel strategy is developed for calculating the rate and spatial distribution of Atlantic N2 fixation, based on isotopic differences between northward- and southward-transported nitrate. (Abstract shortened by ProQuest.).
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
650 4 $a Biological oceanography. $3 1178855
650 4 $a Biogeochemistry. $3 642004
650 4 $a Chemical oceanography. $3 642003
655 7 $a Electronic books. $2 local $3 554714
690 $a 0416
690 $a 0425
690 $a 0403
710 2 $a ProQuest Information and Learning Co. $3 1178819
710 2 $a Princeton University. $b Geosciences. $3 1183380
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10284265 $z click for full text (PQDT)