GREENCYCLESII
T2.4 Jorge Martinez-Rey
The project focuses on the response of the ocean nitrogen cycle to variability in the climatemarine biogeochemical interactions. There have been significant research efforts on modelling to describe the manifold interactions and the several processes involved in the nitrogen cycle. The aim of the project is to improve the marine biogeochemical model PISCES (Aumont and Bopp, 2006) on its nitrogen component through a series of analysis on specific N‐cycle processes. One of the critical issues is the impact of anthropogenic activities on nitrous oxide (N2O) in the ocean. Following the trend on increasing greenhouse gas emissions over the last century (IPCC, 2007), an assessment is required on whether the contributions of oceanic nitrous oxide to the Earth System are likely to increase in future scenarios and which processes are relevant in the ocean. In order to do that, three different forcings will be considered
• External nitrogen input: increased nitrogen contributions from riverine nutrient supply (Seitzinger et al., 2010) and nitrogen atmospheric deposition (Duce et al., 2008, Krishnamurthy, 2009) will be considered for an integral analysis.
• Climate Change: different future scenarios will be defined to see the response of ocean nitrous oxide emissions. It is expected to estimate also a global N2O budget making use of global climate models.
• Ocean acidificacion: effects of the decreased pH in the ocean due to increased CO2 will be evaluated in terms of phytoplankton CNP ratios and volume variability of oxygen minimum zones (OMZ).
The targets of this PhD project demand therefore dealing with up to date atmospheric (INCA model by Hauglustaine et al., 2004) and terrestrial (NEWS2 model by Seitzinger at al., 2010) model output datasets, further development of existing tools (decoupled C/N/P PISCES model version by Tagliabue et al., 2011) for stoichiometry analysis on different phytoplankton types, definition of a variety of climate change scenarios for future estimations (IPCC, Millenium Ecosystem Assesment ‐ MEA), formulation and validation of theoretical assumptions on N2O formation, sensitivity studies with partner institutions' models (UEA and ETH) and also coding of nitrogen isotopic (δ15N) processes into the PISCES model. The work at LSCE will strengthen the PISCES capabilities and aims to shed light onto the N‐cycle uncertainties
References
Aumont, O., and L. Bopp (2006), Globalizing results from ocean in situ iron fertilization studies, Global Biogeochem. Cycles, 20, GB2017.
Denman, K.L., G. Brasseur, A. Chidthaisong, P. Ciais, P.M. Cox, R.E. Dickinson, D. Hauglustaine, C. Heinze, E. Holland, D.Jacob, U. Lohmann, S Ramachandran, P.L. da Silva Dias, S.C. Wofsy and X. Zhang, 2007: Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Duce RA, LaRoche J, Altieri K, Arrigo KR, Baker AR, Capone DG, Cornell S, Dentener F, Galloway J, Ganeshram RS, Geider RJ, Jickells T, Kuypers MM, Langlois R, Liss PS, Liu SM, Middelburg JJ, Moore CM, Nickovic S, Oschlies A, Pedersen T,Prospero J, Schlitzer R, Seitzinger S, Sorensen LL, Uematsu M, Ulloa O, Voss M, Ward B, Zamora L. (2008), Impacts ofatmospheric anthropogenic nitrogen on the open ocean,Science. May 16;320(5878):893‐7.
Hauglustaine, D. A., F. Hourdin, L. Jourdain, M.‐A. Filiberti, S. Walters, J.‐F. Lamarque, and E. A. Holland (2004), Interactive chemistry in the Laboratoire de Météorologie Dynamique general circulation model: Description and background tropospheric chemistry evaluation, J. Geophys. Res., 109, D04314.
Krishnamurthy, A., J. K. Moore, N. Mahowald, C. Luo, S. C. Doney, K. Lindsay, and C. S. Zender (2009), Impacts of increasing anthropogenic soluble iron and nitrogen deposition on ocean biogeochemistry, Global Biogeochem. Cycles, 23, GB3016.
Seitzinger et al., 2010 S.P. Seitzinger, E. Mayorga, A.F. Bouwman, C. Kroeze, A.H.W. Beusen, G. Billen, G. Van Drecht, E. Dumont, B.M. Fekete, J. Garnier and J.A. Harrison (2010), Global river nutrient export: a scenario analysis of past and future trends, Global Biogeochem. Cycles 24, GB0A08.