Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 1 2010 10.5194/bg-7-1-2010 http://www.biogeosciences.net/7/1/2010/ http://www.biogeosciences.net/7/1/2010/bg-7-1-2010.html http://www.biogeosciences.net/7/1/2010/bg-7-1-2010.pdf 1 9 2010-01-04 Increase in water column denitrification during the last deglaciation: the influence of oxygen demand in the eastern equatorial Pacific P. Martinez p.martinez@epoc.u-bordeaux1.fr R. S. Robinson UMR 5805 EPOC, Université Bordeaux 1, avenue des facultés, 33405 Talence cedex, France Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA Here we present organic export production and nitrogen isotope results spanning the last 30 000 years from a core recovered off Costa Rica (Ocean Drilling Program (ODP) Site 1242) on the leading edge of the oxygen minimum zone of the Eastern Tropical North Pacific. Marine export production reveals glacial-interglacial variations with low organic matter (total organic carbon and total nitrogen) contents during warm intervals, twice more during cold episodes and double peaked maximum during the deglaciation, between ~15.5–18.5 and 11–13 ka B.P. When this new export production record is compared with four nearby cores from within the Eastern Pacific along the Equatorial divergence, good agreement between all the cores is observed. The major feature is a maximum of export during the early deglaciation. As for export production, water-column denitrification, represented by sedimentary δ¹⁵N records, along the Eastern tropical North and South Pacific between 15° N and 36° S is also coherent over the last deglaciation. Each of the nitrogen isotope profiles indicate that denitrification increased abruptly at 19 ka B.P to a maximum during the early deglaciation, confirming a typical Antarctic timing. It is proposed that the increase in export production and then in subsurface oxygen demand lead to an intensification of water-column denitrification within the oxygen minimum zones in the easternmost Pacific at the time of the last deglaciation. The triggering mechanism would have been primarily linked to an increase in preformed nutrients contents feeding the Equatorial Undercurrent driven by the resumption of overturning in the Southern Ocean and the return of nutrients from the deep ocean to the sea-surface. An increase in equatorial wind-driven upwelling of sub-surface nutrient-rich waters could have played the role of an amplifier. Altabet, M. A., Francois, R., Murray, D. E., and Prell, W. L.: Climate-related variations in denitrification in the Arabian Sea from sediment $^15$N/$^14$N ratios, Nature, 373, 506–509, 1995. Altabet, M. A., Higginson, M. J., and Murray, D. W.: The effect of millennial-scale changes in Arabian Sea denitrification on atmospheric CO₂, Nature, 415, 159–162, 2002. Altabet, M. A., Murray, D. W., and Prell, W. L.: Climatically linked oscillations in Arabian Sea denitrification over the past 1 m.y.: Implications for the marine N cycle, Paleoceanography, 14, 732–743, 1999. Benway, H. M., Mix, A. C., Haley, B. A., and Klinkhammer, G. P.: Eastern Pacific Warm Pool paleosalinity and climate variability: 0–30 kyr, Paleoceanography, 21, PA3008, doi:10.1029/2005PA001208, 2006. Bertrand, P., Shimmield, G., Martinez, P., Grousset, F., Jorissen, F., Paterne, M., Pujol, C., Bouloubassi, I., Buat-Ménard, P., Peypouquet, J.-P., Beaufort, L., Sicre, M.-A., Lallier-Vergès, E., Foster, J. M., Ternois, Y:: The glacial ocean productivity hypothesis: the importance of regional temporal and spatial studies, Mar. Geol. 130, 1–9, 1996. Bradtmiller, L. I., Anderson, R. F., Fleisher, M. Q., and Burckle L. H.: Diatom productivity in the equatorial Pacific Ocean from the last glacial period to the present: A test of the silicic acid leakage hypothesis, Paleoceanography, 21, PA4201, doi:10.1029/2006PA001282, 2006. Brunelle, B. G., Sigman, D. M., Cook, M. S., Keigwin, L. D., Haug, G. H., Plessen, B., Schettler, G., and Jaccard, S. L.: Evidence from diatom-bound nitrogen isotopes for subarctic Pacific stratification during the last ice age and a link to North Pacific denitrification changes, Paleoceanography, 22, PA1215, doi:10.1029/2005PA001205, 2007. Bush, A. B. G. and Philander, G. H.: The Role of Ocean-Atmosphere Interactions in Tropical Cooling During the Last Glacial Maximum, Science, 279, 1341–1344, 1998. Calvert, S. E. and Pedersen, T. F.: Elemental proxies for palaeoclimatic and palaeoceanographic variability in marine sediments: in: Interpretation and application, edited by: Hilaire-Marcel C. and de Vernal, A., Methods in Late Cenozoic, Paleoceanography, Elsevier, 567–644, 2007. Chazen, C. R., Altabet, M., and Herbert, T. D.: Mid-Holocene onset of high-amplitude decadal to centennial scale variability along the Peru Chile Margin American Geophysical Union, Fall Meeting, 2008. Codispoti, L. A., Yoshinari, T., and Devol, A. H.: Suboxic respiration in the oceanic water column, in: Respiration in Aquatic Ecosystems, edited by: del Giorgio, P. A. and Williams, P. J. Le B., Oxford University Press, 225–247, 2005. De Pol-Holz, R., Ulloa, O., Dezileau, L., Kaiser, J., Lamy, F., and Hebbeln, D.: Melting of the Patagonian ice sheet and deglacial perturbations of the nitrogen cycle in the eastern South Pacific, Geophy. Res. Lett., 33, L04704, doi:10.1029/2005GL024477, 2006. De Pol-Holz, R., Ulloa, O., Lamy, F., Dezileau, L., Sabatier, L., and Hebbeln, D.: Late Quaternary variability of sedimentary nitrogen isotopes in the eastern South Pacific Ocean, Paleoceanography, 22, PA2207, doi:10.1029/2006PA001308, 2007. Farrell, J. W., Pedersen, T. F., Calvert, S. E., and Nielsen, B.: Glacial/interglacial changes in nutrient utilization in the equatorial Pacific Ocean, Nature, 377, 514–517, 1995. Francois, R., Frank, M., Rutgers van der Loeff, M., and Bacon, M. P.: $^230$Th-normalization: an essential tool for interpreting sedimentary fluxes during the late Quaternary, Paleoceanography, 19(1), PA1018, doi:10.1029/2003PA000939, 2004. Galbraith, E. D., Kienast, M., Pedersen, T. F., and Calvert, S. E.: Glacial-interglacial modulation of the marine nitrogen cycle by high-latitude O₂ supply to the global thermocline, Paleoceanography, 19, PA4007, doi:10.1029/2003PA001000, 2004. Galbraith, E. D.: Interactions between climate and the marine nitrogen cycle on glacial-interglacial timescales, PhD Thesis, Vancouver University of British Colombia, 2006. Ganeshram, R. J., Pedersen, T. F., Calvert, S. E., and Murray, J. W.: Large changes in nutrient inventories from glacial to interglacial periods, Nature, 376, 755–758, 1995. Ganeshram, R. J., Pedersen, T. F., Calvert, S. E., McNeill, G. W., and Fontugne, M. R.: Glacial-interglacial variability in denitrification in the World's Oceans: Causes and consequences, Paleoceanography, 15, 361–376, 2000. Garcia, H. E., Locarnini, R. A., Boyer, T. P., and Antonov, J. I.: World Ocean Atlas~2005, Volume~3: Dissolved Oxygen, Oxygen Utilization and Oxygen Saturation, US Government Printing Office, Washington DC, 342~pp., 2006. Hendy, I. L., Pedersen, T. F., Kennett, J. P., and Tada, R.: Intermittent existence of a southern Californian upwelling cell, Paleoceanography, 19, PA3007, doi:10.1029/2003PA000965, 2004. Hendy, I. L. and Pedersen T. F.: Oxygen minimum zone expansion in the eastern tropical North Pacific during deglaciation, Geophys. Res. Lett., 33, L20602, doi:10.1029/2006GL025975, 2006. Higginson, M. J. and Altabet, M. A.: Initial test of the silicic acid leakage hypothesis using sedimentary biomarkers, Geophys. Res. Lett., 31, L18303, doi:10.1029/2004GL020511, 2004. Jaccard, S. L., Galbraith, E. D., Sigman, D. M., Haug, G. H., Francois, R., Pedersen, T. F., Dulski, P., and Thierstein, H. R.: Subarctic Pacific evidence for a glacial deepening of the oceanic respired carbon pool: Earth Planet. Sci. Lett., 277, 156–165, 2009. Kao, S. J., Liu, K. K., Hsu, S. C., Chang, Y. P., and Dai, M. H.: North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific, Biogeosciences, 5, 1641–1650, 2008. Kiefer, T. and Kienast, M.: Patterns of deglacial warming in the Pacific Ocean: a review with emphasis on the time interval of Heinrich event 1, Quaternary Sci. Rev., 24, 1063–-1081, 2005. Kienast, S. S., Calvert, S. E., and Pedersen, T. F.: Nitrogen isotope and productivity variations along the northeast Pacific margin over the last 120 kyr: Surface and subsurface paleoceanography, Paleoceanography, 17, 1055, doi:10.1029/2001PA000650, 2002. Kienast, S. S., Kienast, M., Jaccard, S., Calvert, S. E., and François, R.: Testing the silica leakage hypothesis with sedimentary records from the eastern equatorial Pacific over the last 150 kyrs, Geophy. Res. Lett., 33, L15607, doi:10.1029/2006GL026651, 2006. Kienast, S. S., Mix, A. C., Calvert, S. E., and François, R.: Thorium-230 normalized particle flux and sediment focusing in the Panama region during the last 30,000 years, Paleoceanography, 22, PA2213, doi:10.1029/2006PA001357, 2007. Kienast, M., Kienast, S. S., Calvert, S. E., Eglinton, T. I., Mollenhauer, G., Francois, R., and Mix, A. C.: Eastern Pacific cooling and Atlantic overturning circulation during the last deglaciation, Nature, 443, 846–848, 2006. Kienast, M., Lehmann, M., Timmermann, A., Galbraith, E., Bolliet, T., Holbourn, A., Normandeau, C., and Laj, C.: A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline?, Geophy. Res. Lett., 35, L23610, doi:10.1029/2008GL035464, 2008. Klinkhammer, G. P., Mix, A. C., and Haley, B. A.: Increased dissolved terrestrial input to the coastal ocean during the last deglaciation, Geochem. Geophy. Geosy., 10(3), Q03009, doi:10.1029/2008GC002219, 2009. Koutavas, A., Lynch-Stieglitz, J., Marchitto, T. M., and Sachs, J. P.: El Nino-like pattern in ice age tropical Pacific sea surface temperature, Science, 297, 226–230, 2002. Lea, D., Pak, D. K., Belanger, C. L., Spero, H. J., Hall, M. A., Shackleton, N. J., et al.: Paleoclimate history of Galapagos surface waters over the last 135,000 yr., Quat. Sci. Rev., 25, 1152–1167, 2006. Loubere, P., Richaud, M., and Mireles, S.: Variability in tropical thermocline nutrient chemistry on the glacial/interglacial timescale, Deep-Sea Res. II, 54, 747–761, 2007. Loubere, P.: Remote vs local control of changes in eastern equatorial Pacific bioproductivity from the Last Glacial Maximum to the Present, Global Planet Change, 35, 113–126, 2002. Lukas, R.: The termination of the Equatorial Undercurrent in the Eastern Pacific, Progr. Oceanogr., 16, 63–90, 1986. Marchitto, T. M., Lehman, S. J., Ortiz, J. D., Flückiger, J., and van Geen, A.: Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO₂, Science, 316, 1456–1459, 2007. Martinez, P., Lamy, F., Robinson, R. S., Pichevin, L., and Billy, I.: Atypical $\delta^15$N variations at the southern boundary of the east Pacific oxygen minimum zone over the last 50 kyr, Quat. Sci. Rev., 25, 3017–3028, 2006. Meissner, K. J., Galbraith, E. D., and Völker, C.: Denitrification under glacial and interglacial conditions: A physical approach, Paleoceanography, 20, PA3001, doi:10.1029/2004PA001083, 2005. Meyers, P. A.: Organic geochemical proxies of paleoceanographic, paleolimnologic and paleoclimatic processes, Org. Geochem., 27(5/6), 213–250, 1997. Mix, A. C., Tiedemann, R., and Blum, P., shipboard scientists: Southeast Pacific Paleoceanographic Transects, Initial Reports. vol. 202. ODP, Texas A&M University, 2003. Mollenhauer, G., Eglinton, T. I., Ohkouchi, N., Schneider, R. R., Müller, P. J., Grootes, P. M., Rullkörter, J., et al.: Asynchronous alkenone and foraminifera records from the Benguela Upwelling System, Geochim. Cosmochim. Ac., 67, 2157–2171, 2003. Müller, P. J.: C/N ratio in Pacific deep-sea sediments: effect of inorganic ammonium and organic nitrogen compounds sorbed by clays, Geochim. Cosmochim. Ac., 41, 765–776, 1977. Pahnke, K. and Zahn, R.: Southern Hemisphere water mass conversion linked with North Atlantic climate variability, Science, 307(5716), 1741–1746, 2005. Pedersen, T. F., Nielsen, B., and Pickering, M.: Timing of Late Quaternary productivity pulses in the Panama Basin and implications for atmospheric CO2, Paleoceanography, 6, 657–677, 1991. Pena, L. D., Cacho, I., Ferretti, P., and Hall, M. A.: ENSO-like variability during glacial terminations and interlatitudinal tele-connections, Paleoceanography, 23, PA3101, doi:10.1029/2008PA001620, 2008. Pennington, J. T., Mahoney, K. L., Kuwahara, V. S., Kolber, D. D., Calienes, R., and Chavez, F. P.: Primary production in the eastern tropical Pacific: A review, Progr. Oceanogr., 69, 285–317, 2006. Pichevin, L. E., Reynolds, B. C., Ganeshram, R. S., Cacho, I., Pena, L., Keefe, K., and Ellam, R. M.: Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean, Nature, 459, 1114–1118, doi:10.1038/nature08101, 2009. Pichevin, L. E., Ganeshram, R. S., Francavilla, S., Arellano-Torres, E., Pedersen, T. F., and Beaufort, L.: Inter-hemispheric leakage of isotopically heavy nitrate in the Eastern Tropical Pacific during the last glacial period, Paleoceanography, in press., 2009. Pride, C., Thunell, R., Sigman, D., Keigwin, L., Altabet, M., and Tappa, E.: Nitrogen isotopic variations in the Gulf of California since the last deglaciation: Response to global climate change, Paleoceanography, 14, 397–409, 1999. Ren, H., Sigman, D. M., Meckler, A. N., Plessen, B., Robinson, R. S., Rosenthal, Y., and Haug, G. H.: Foraminiferal isotope evidence of reduced nitrogen fixation in the ice age Atlantic Ocean, Science, 323, 244–248, doi:10.1126/science.1165787, 2009. Robinson, R. S., Mix, A., and Martinez, P.: Southern Ocean control on the extent of denitrification in the southeast Pacific over the last 70 ky, Quat. Sci. Rev., 26, 2001–2212, 2007. Robinson, R. S., Sigman, D. M., DiFiore, P. J., Rohde, M. M., Mashiotta, T. A., and Lea, D. W.: Diatom-bound $^15$N/$^14$N: New support for enhanced nutrient consumption in the ice age Subantarctic, Paleoceanography, 20, PA3003, doi:10.1029/2004PA2004001114, 2005. Robinson, R. S., Martinez, P., Pena, L. D., and Cacho, I.: Nitrogen isotopic evidence for deglacial changes in nutrient supply in the Eastern Equatorial Pacific, Paleoceanography, 24, PA4213, doi:10.1029/2008PA001702, 2009. Sarmiento, J. L., Gruber, N., Brzezinski, M. A., and Dunne, J. P.: High-latitude controls of thermocline nutrients and low latitude biological productivity, Nature, 427, 56–60, 2004. Schmittner, A., Galbraith, E. D., Hostetler, S. W., Pedersen, T. F., and Zhang, R.: Large fluctuations of dissolved oxygen in the Indian Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction, Paleoceanography, 22, PA3207, doi:10.1029/2006PA001384, 2007. Spero, H. J. and Lea, D. W.: The cause of carbon isotope minimum events on glacial terminations, Science, 296, 522–525, 2002. Thunell, R. C. and Kepple, A. B.: Glacial-Holocene $\delta^15$N record from the Gulf of Tehuantepec, Mexico: implications for denitrification in the eastern equatorial Pacific and changes in atmospheric N2O, Glob. Biogeochem. Cy., 18, GB1001, doi:10.1029/2002GB002028, 2004. Toggweiler, J. R., Dixon, K., and Broecker, W. S.: The Peru Upwelling and the Ventilation of the South-Pacific Thermocline, J. Geophys. Res.-Oceans, 96, 20467–20497, 1991.