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Lehmann, Nadine; Granger, Julie; Kienast, Markus; Brown, Kevin S; Rafter, Patrick A; Martínez Méndez, Gema; Mohtadi, Mahyar (2018): Isotopic composition of nitrate and DIC and physical oceanography along the western equatorial Pacific. PANGAEA,, Supplement to: Lehmann, N et al. (2018): Isotopic evidence for the evolution of subsurface nitrate in the Western Equatorial Pacific. Journal of Geophysical Research: Oceans, 123(3), 1684-1707,

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Subsurface waters from both hemispheres converge in the Western Equatorial Pacific (WEP), some of which form the Equatorial Undercurrent (EUC) that influences equatorial Pacific productivity across the basin. Measurements of nitrogen (N) and oxygen (O) isotope ratios in nitrate (d15N-NO3 and d18O-NO3), the isotope ratios of dissolved inorganic carbon (d13C-DIC), and complementary biogeochemical tracers reveal that northern and southern WEP waters have distinct biogeochemical histories. Organic matter remineralization plays an important role in setting the nutrient characteristics on both sides of the WEP. However, remineralization in the northern WEP contributes a larger concentration of the nutrients, consistent with the older "age" of northern thermocline- and intermediate-depth waters. Remineralization introduces a relatively low d15N-NO3 to northern waters, suggesting the production of sinking organic matter by N2 fixation at the surface - consistent with the notion that N2 fixation is quantitatively important in the North Pacific. In contrast, remineralization contributes elevated d15N-NO3 to the southern WEP thermocline, which we hypothesize to derive from the vertical flux of high-d15N material at the southern edge of the equatorial upwelling. This signal potentially masks any imprint of N2 fixation from South Pacific waters. The observations further suggest that the intrusion of high d15N-NO3 and d18O-NO3 waters from the eastern margins is more prominent in the northern than southern WEP. Together, these north-south differences enable the examination of the hemispheric inputs to the EUC, which appear to derive predominantly from southern hemisphere waters.
Median Latitude: 0.382411 * Median Longitude: 138.652478 * South-bound Latitude: -7.889167 * West-bound Longitude: 125.848167 * North-bound Latitude: 8.326333 * East-bound Longitude: 150.861333
Date/Time Start: 2013-05-09T00:00:00 * Date/Time End: 2013-06-13T00:45:00
Minimum DEPTH, water: 0.14 m * Maximum DEPTH, water: 4100.00 m
GeoB17401-1 * Latitude: 8.326333 * Longitude: 126.909667 * Date/Time: 2013-05-09T00:00:00 * Elevation: -5155.0 m * Campaign: SO228 (EISPAC/WESTWIND) * Basis: Sonne * Device: CTD/Rosette (CTD-RO)
GeoB17403-1 * Latitude: 7.824500 * Longitude: 126.678500 * Date/Time: 2013-05-11T07:55:00 * Elevation: -1438.0 m * Campaign: SO228 (EISPAC/WESTWIND) * Basis: Sonne * Device: CTD/Rosette (CTD-RO)
GeoB17404-1 * Latitude: 7.900333 * Longitude: 126.543333 * Date/Time: 2013-05-12T00:12:00 * Elevation: -407.0 m * Campaign: SO228 (EISPAC/WESTWIND) * Basis: Sonne * Device: CTD/Rosette (CTD-RO)
D(15-18) refers to the difference in d15N and d18O of nitrate.
Si* represents the difference between silicic acid and nitrate concentrations.
#NameShort NameUnitPrincipal InvestigatorMethodComment
1Event labelEventLehmann, Nadine
2Latitude of eventLatitudeLehmann, Nadine
3Longitude of eventLongitudeLehmann, Nadine
4Elevation of eventElevationmLehmann, Nadine
5Date/Time of eventDate/TimeLehmann, Nadine
6DEPTH, waterDepth watermLehmann, NadineGeocode
7Pressure, waterPressdbarLehmann, NadineAveraged 100
8Temperature, waterTemp°CLehmann, Nadine
9SalinitySalLehmann, Nadine
10Density, mass densityDensitykg/m3Lehmann, NadineAveraged 100
11Density, sigma-theta (0)Sigma-thetakg/m3Lehmann, NadineAveraged 100
12OxygenO2µmol/lLehmann, Nadine
13Oxygen saturationO2 sat%Lehmann, NadineAveraged 100
14δ13C, dissolved inorganic carbonδ13C DIC‰ PDBLehmann, Nadinewater
15δ13C, dissolved inorganic carbon, standard deviationδ13C DIC std dev±Lehmann, Nadine
16Nitrate[NO3]-µmol/lLehmann, Nadine
17Phosphate[PO4]3-µmol/lLehmann, Nadine
18SilicateSi(OH)4µmol/lLehmann, Nadine
19δ15N, nitrateδ15N NO3‰ airLehmann, NadineAVG
20δ15N, nitrate, standard deviationδ15N NO3 std dev±Lehmann, Nadine
21δ18O, nitrateδ18O NO3Lehmann, NadineAVG
22δ18O, standard deviationδ18O std dev±Lehmann, Nadine
23DifferenceDiffLehmann, NadineDelta(15-18)
24DifferenceDiffLehmann, NadineSi*
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