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| Kienast, M.; Lehmann, M. F.; Timmermann, A.; Galbraith, E.; Bolliet, T.; Holboum, A.; Normandeau, C.; Laj, C.. |
| Sedimentary delta(15)N records from the oligotrophic western equatorial Pacific (WEP) off Mindanao show that late Holocene sedimentary delta(15)N is substantially lower than that of the early Holocene, following a gradual >3 parts per thousand decrease that occurred between 7 and 3 kyrs ago. Analyses of modem day nitrate isotope profiles from the same region indicate the sensitivity of the WEP N pools towards (1) the advection of (15)N-enriched nitrate from the Eastern Equatorial Pacific (EEP) by the North Equatorial Current (NEC) and the Mindanao Current in subsurface waters and, (2) at shallow depths, the input of new and (15)N-depleted nitrate through N, fixation. We suggest that the Holocene decrease in sedimentary delta(15)N reflects a diminished... |
| Tipo: Text |
Palavras-chave: Tropical Pacific; El Nino; Surface temperature; Fresh water; Nitrate; Mindanao; Ocean; Variability; Holocene; Seawater. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00207/31843/30257.pdf |
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| Kienast, M.; Macintyre, G.; Dubois, N.; Higginson, S.; Normandeau, C.; Chazen, C.; Herbert, T. D.. |
| Significant uncertainties persist in the reconstruction of past sea surface temperatures in the eastern equatorial Pacific, especially regarding the amplitude of the glacial cooling and the details of the post-glacial warming. Here we present the first regional calibration of alkenone unsaturation in surface sediments versus mean annual sea surface temperatures (maSST). Based on 81 new and 48 previously published data points, it is shown that open ocean samples conform to established global regressions of U-K' 37 versus maSST and that there is no systematic bias from seasonality in the production or export of alkenones, or from surface ocean nutrient concentrations or salinity. The flattening of the regression at the highest maSSTs is found to be... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00265/37673/36760.pdf |
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