Dr. Christopher Somes


Scientist at Research Unit Biogeochemical Modelling

Room: 5.515
Tel.: +49 431 600-2053
E-Mail: csomes(at)geomar.de

GEOMAR Helmholtz Centre for Ocean Research Kiel
Wischhofstr. 1-3
24148 Kiel, Germany

Twitter (@SomesOcean)
BlueSky (@SomesOcean.bsky.social)

CV download

Research Bio

I am a scientist interested in understanding how ocean biology and chemistry are affected by environmental change such as pollution and climate. I use global Earth system climate models to predict their response and associated feedbacks on the Earth’s climate system. My research focuses on analyzing and interpreting elemental isotopic ratios to gain insights and constraints on marine biogeochemical cycling and ecosystem dynamics in the modern ocean, as well as during past climate change events recorded in ocean sediments. This helps us to better understand the impacts of climate change on marine biology and chemistry, and thus improve our predictions of the future ocean and climate.

Research Interests

  • Climate change feedbacks associated with marine biogeochemistry in the past, present, and future ocean
  • Impact of anthropogenic nutrient pollutants on ocean deoxygenation and marine ecosystems
  • Nutrient co-limitation of marine phytoplankton growth
  • Isotopic constraints and insights on ocean biogeochemical cycling and marine ecosystem dynamics
  • Development of ocean biogeochemical, ecosystem, and Earth system models


Current Projects

ISOIRON Project (DFG page)

Isotopic constraints on global marine iron cycling, ocean productivity and deoxygenation

  • German Research Foundation (Deutsche Forschungsgemeinschaft)
  • Position: Principal Investigator
  • 2023-2026


ISODEG Project (DFG page)

Isotopic constraints on declining marine nutrient inventories weakening the soft-tissue biological carbon pump during the last deglaciation

  • German Research Foundation (Deutsche Forschungsgemeinschaft)
  • Position: Principal Investigator
  • 2021-2025

Submitted / In Press / Just Published Articles

  • Li N., Somes C.J., Landolfi A., Chien C.-T., Pahlow M., Oschlies A. (submitted prepint), Global impact of benthic denitrification on marine N2 fixation and primary production simulated by a variable stoichiometry Earth system model, EGUspherehttps://doi.org/10.5194/egusphere-2024-123

  • Hoogakker B. et al. (submitted preprint), Review and syntheses: Review of proxies for low-oxygen paleoceanographic reconstructions, EGUsphere, https://doi.org/10.5194/egusphere-2023-2981

  • Heinze C. et al. (submitted preprint), Review and syntheses: Abrupt ocean biogeochemical change under human-made climatic forcing - warming, acidification, and deoxygenation, Biogeosciences Discuss., https://doi.org/10.5194/bg-2023-182

  • Golikov A.V., Xavier J.C., Ceia F.R., Queiros J.P., Bustamante P., Couperus B., Guillou G., Larionova A.M., Sabirov R.M., Somes C.J., Hoving H.-J. (in press), Insights on long-term ecosystem changes from stable isotopes in historical squid beaks, BMC Ecology and Evolutionhttps://doi.org/10.1186/s12862-024-02274-7

  • Frenger I., Landolfi A., Kvale K., Somes C.J., Oschlies A., Yao W., Koeve W. (in press), Misconceptions of the marine biological carbon pump in a changing climate: Thinking outside the "export" box, Global Change Biologyhttps://doi.org/10.1111/gcb.17124



  • Pelz M.-T., Schartau M., Somes C.J., Lampe V., Slawig T. (2023): A diffusion-based kernel density estimator (diffKDE, version 1) with optimal bandwidth approximation for the analysis of data in geoscience and ecological research, Geoscientific Model Development, 16, 6609-6634, https://doi.org/10.5194/gmd-16-6609-2023

  • Derville S., Torres L.G., Newsome S., Somes C.J, Valenzuela L.O., Zanden H.B.V., et al., Carroll E.L. (2023): Long-term stability in the circumpolar foraging range of a Southern Ocean predator between the eras of whaling and rapid climte change, Proceedings of the National Academy of Sciences, 120 (10), e2214035120, https://doi.org/10.1073/pnas.2214035120


  • Wallmann K., José Y.S., Hopwood M.J., Somes, C.J., Dale A.W., Scholz F., Achterberg E.P., Oschlies A. (2022), Biogeochemical feedbacks may amplify ongoing and future deoxygenation: a case study from the Peruvian oxygen minimum zone, Biogeochemistry, 159, 45-67, e2021GB006948,  https://doi.org/10.1007/s10533-022-00908-w

  • Pelz M.-T., Somes C.J., Tuerena R.E., Lorrain A., Close H.G., Henderson L.C., St. John Glew K., Espinasse B., Trueman C.N. (2022): A global marine particulate organic carbon-13 isotope data product (Version2). PANGAEAhttps://doi.org/10.1594/PANGAEA.946915


  • Bodin N., Pethybridge H., Duffy L.M., Lorrain A., Allain V., Logan J.M., Ménard F., Graham B., Choy C.A., Somes C.J., Olson R.J., Young J.W. (2021), Global data set for nitrogen and carbon stable isotopes of tunas, Ecology, 102(3):e03265, https://doi.org/10.1002/ecy.3265

  • Farmer J., Hertzberg J.E., Cardinal D., Fietz F., Hendry K., Jaccard S.L., Paytan A., Rafter P.A., Ren H., Somes C.J., Sutton J.N., and the GEOTRACES-PAGES Biological Productivity Working Group Members (2021), Assessment of C, N, and Si isotopes as tracers of past ocean nutrient and carbon cycling, Global Biogeochemical Cycles, 35, e2020GB006775, https://doi.org/10.1029/2020GB006775

  • Kvale K., Keller D.P., Koeve W., Meissner K.J., Somes C.J., Yao W., Oschlies A. (2021), Explicit silicate cycling in the Kiel Marine Biogeochemistry Model, version 3 (KMBM3) embedded in the UVic ESCM version 2.9, Geoscientific Model Development , 14, 7255-7285, https://doi.org/10.5194/gmd-14-7255-2021

  • Landolfi A., Prowe F.A.E., Pahlow M., Somes C.J., Chien C.-T., Schartau M., Koeve W., Oschlies A. (2021), Can top-down controls expand the ecological niche of marine N2 fixers?, Frontiers in Microbiology, 12:690200, https://doi.org/10.3389/fmicb.2021.690200

  • Mèdieu A., Point D., Receveur A., Gauthier O., Allain V., Pethybridge H., Menkes C.E., Gillikin D.P., Revill A.T., Somes C.J., Collin J., Lorrain A. (2021), Stable mercury concentrations of tropical tuna in the south western Pacific Ocean: an 18-year monitoring study, Chemosphere, 263:128024. https://doi.org/10.1016/j.chemosphere.2020.128024

  • Somes, C.J., Dale A.W., Wallmann K., Scholz F., Yao W., Oschlies A., Muglia J., Schmittner A., Achterberg E.P. (2021), Constraining global marine iron sources and ligand-mediated scavenging fluxes with GEOTRACES dissolved iron measurements in a global ocean biogeochemical model, Global Biogeochemical Cycles, 35, e2021GB006948,  https://doi.org/10.1029/2021GB006948

  • St. John Glew K., Espinasse B., Hunt B.P.V, Pakhomov E.A., Bury S.J., Pinkerton M.H., Nodder S.D., Gutierrez-Rodrigues A., Safi K., Brown J.C.S., Graham L., Dunbar R.B., Mucciarone D.A., Magozzi S., Somes C.J., Trueman C. (2021), Isoscape Models of the Southern Ocean: Predicting Spatial and Temporal Variability in Carbon and Nitrogen Isotope Compositions of Particulate Organic MatterGlobal Biogeochemical Cycles, 35, e2020GB006901, https://doi.org/10.1029/2020GB006901

  • Verwega T.-M., Somes C.J., Schartau M., Lorrain A., Tuerena R.E., Oschlies A., Slawig T. (2021), Description of a global marine pariculate organic carbon-13 data set, Earth Syst. Sci. Data, 13, 4861-4880, https://doi.org/10.5194/essd-13-4861-2021


  • Lorrain, A., Pethybridge, H., Cassar, N., Receveur, A., Allain, V., Bodin, N., Bopp, L., Choy, C.A., Duffy, L., Fry, B., Goñi, N., Graham, B.S., Hobday, A.J., Logan, J.M., Ménard, F., Menkes, C., Olson, D.E., Pagendam, R.J., Point, D., Revill, A.T., Somes, C.J., Young, J.W. (2020), Trends in tuna isotopes suggest global changes in pelgic phytoplankton communities, Global Change Biology, 26:458-470. https://doi.org/10.1111/gcb.14858

  • Logan J.M., Pethybridge H., Lorrain A., Somes C.J., Allain V., Bodin N., Choy C.A., Duffy L., Goñi N., Graham B., Langlais C., Ménard F., Olson R., Young J. (2020), Global patterns and inferences of tuna movements and trophodynamics, Deep Sea Research II, 175:104775. https://doi.org/10.1016/j.dsr2.2020.104775

  • Dhureea Z., Pethybridge H., Langlais C., Somes C.J., Nikolic N., Bourjea J., Appadoo C., Bodin N. (2020), Spatial variation in stable isotopes and fatty acid trophic markers in albacore tuna (Thunnus alalunga) from the western Indian Ocean, Deep Sea Research I, 161:103286, https://doi.org/10.1016/j.dsr.2020.103286


  • Pethybridge, H., Choy, C.A., Logan, L.M., Allain, V., Lorrain, A., Bodin, N., Somes, C.J., Young, J., Menard, F., Langlais, C., Duffy, L., Hobday, A.J., Kuhnert, P., Fry, B., Menkes, C., Olson, R.J. (2018). A global meta-analysis of marine predator nitrogen stable isotopes: Relationships between trophic structure and environmental conditions. Global Ecology and Biogeography, 2018;00:1-13.  doi:10.1111/geb.12763

  • Glock, N., Erdem, Z., Wallmann, K., Somes, C. J., Liebtrau, V., Schönfeld, J., Gorb, S.,  Eisenhauer, A. (2018). Coupling of oceanic carbon and nitrogen facilitates spatially resolved quantitative reconstruction of nitrate inventories. Nature Communications, 9:1217.  doi:10.1038/s41467-018-03647-5


  • Muglia, J., Somes, C., Nickelsen, L. and Schmittner, A. (2017). Combined Effects of Atmospheric and Seafloor Iron Fluxes to the Glacial OceanPaleoceanography, 32, 1204-1218.  doi:10.1002/2016PA003077

  • Landolfi, A., Somes, C. J., Koeve, W., Zamora, L. M. and Oschlies, A. (2017) Oceanic nitrogen cycling and N2O flux perturbations in the Anthropocene. Global Biogeochemical Cycles, 31 (8), 1236-1255.  doi10.1002/2017GB005633

  • Somes, C. J., Schmittner, A., Muglia, J. and Oschlies, A. (2017). A Three-Dimensional Model of the Marine Nitrogen Cycle during the Last Glacial Maximum Constrained by Sedimentary IsotopesFrontiers in Marine Science, 4:108. doi:10.3389/fmars.2017.00108


  • Schmittner, A. and Somes, C. J. (2016). Complementary constraints from carbon (13C) and nitrogen (15N) isotopes on the glacial ocean's soft-tissue biological pumpPaleoceanography, 31 (6), 669-693. doi:10.1002/2015PA002905

  • Somes, C. J., Landolfi, A., Koeve, W. and Oschlies, A. (2016). Limited impact of atmospheric nitrogen deposition on marine productivity due to biogeochemical feedbacks in a global ocean model. Geophysical Research Letters, 43 (9), 4500-4509. doi:10.1002/2016GL068335


  • Somes, C. J. and Oschlies, A. (2015). On the influence of “non-Redfield” dissolved organic nutrient dynamics on the spatial distribution of Nfixation and the size of the marine fixed nitrogen inventory. Global Biogeochemical Cycles, 29 (7), 973-993. doi:10.1002/2014GB005050

  • Young, J. W., Olson, R. J., Ménard, F., Kuhnert, P. M., Duffy, L. M., Allain, V., Logan, J. M., Lorrain, A., Somes, C. J., Graham, B., Goñi, N., Pethybridge, H., Simier, M., Potier, M., Romanov, E., Pagendam, D., Hannides, C. and Choy, C. A. (2015). Setting the stage for a global-scale trophic analysis of marine top predators: a multi-workshop review. Reviews in Fish Biology and Fisheries, 25 (1), 261-272. doi:10.1007/s11160-014-9368-4


  • Moore, R. M., Kienast, M., Fraser, M., Cullen, J. J., Deutsch, C., Dutkiewicz, S., Follows, M. J. and Somes, C. J. (2014). Extensive hydrogen supersaturations in the western South Atlantic Ocean suggest substantial underestimation of nitrogen fixationJournal of Geophysical Research Oceans, 119 (7), 4340-4350. doi:10.1002/2014JC010017


  • Navarro, J., Coll, M., Somes, C. J. and Olson, R. J. (2013). Trophic niche of squids: Insights from isotopic data in marine systems worldwideDeep-Sea Research II, 95, 93-102. doi:10.1016/j.dsr2.2013.01.031

  • Somes, C. J., Oschlies, A. and Schmittner, A. (2013). Isotopic constraints on the pre-industrial oceanic nitrogen budgetBiogeosciences, 10 (9), 5889-5910. doi:10.5194/bg-10-5889-2013

  • Galbraith, E. D., Kienast, M., Galbraith, E. D., Kienast, M., Albuquerque, A. L., Altabet, M. A., Batista, F., Bianchi, D., Calvert, S. E., Contreras, S., Crosta, X., De Pol-Holz, R., Dubois, N., Etourneau, J., Francois, R., Hsu, T. C., Ivanochko, T., Jaccard, S. L., Kao, S. J., Kiefer, T., Kienast, S., Lehmann, M. F., Martinez, P., McCarthy, M., Meckler, A. N., Mix, A., Möbius, J., Pedersen, T. F., Pichevin, L., Quan, T. M., Robinson, R. S., Ryabenko, E., Schmittner-Boesch, A., Schneider, R., Schneider-Mor, A., Shigemitsu, M., Sinclair, D., Somes, C. J., Studer, A. S., Tesdal, J. E., Thunell, R. and Terence Yang, J. Y. (2013). The acceleration of oceanic denitrification during deglacial warmingNature Geoscience, 6, 579-584. doi:10.1038/ngeo1832


  • Robinson, R. S., Kienast, M., Luiza Albuquerque, A., Altabet, M., Contreras, S., De Pol Holz, R., Dubois, N., Francois, R., Galbraith, E., Hsu, T. C., Ivanochko, T., Jaccard, S., Kao, S. J., Kiefer, T., Kienast, S., Lehmann, M., Martinez, P., McCarthy, M., Möbius, J., Pedersen, T., Quan, T. M., Ryabenko, E., Schmittner, A., Schneider, R., Schneider-Mor, A., Shigemitsu, M., Sinclair, D., Somes, C. J., Studer, A., Thunell, R. and Yang, J. Y. (2012). A review of nitrogen isotopic alteration in marine sedimentsPaleoceanography, 27 (4), PA4203. doi:10.1029/2012PA002321


  • Somes, C. J., Schmittner, A. and Altabet, M. A. (2010). Nitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific OceanGeophysical Research Letters, 37 (23), L23605. doi:10.1029/2010GL044537

  • Somes, C. J., Schmittner, A., Galbraith, E. D., Lehmann, M. F., Altabet, M. A., Montoya, J. P., Letelier, R. M., Mix, A. C., Bourbonnais, A. and Eby, M. (2010). Simulating the global distribution of nitrogen isotopes in the oceanGlobal Biogeochemical Cycles, 24 (4), GB4019. doi:10.1029/2009GB003767


  • Somes, C. J. (2013). Nitrogen Isotopes in the Global OceanDoctoral (PhD) dissertation, Christian-Albrechts-University of Kiel, Kiel, Germany, 141 pp. (url)
  • Somes, C. J. (2009). Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixationMaster's thesis, Oregon State University, Corvallis, Oregon, USA, 72 pp., (url)


  • Ph.D, Oceanography, GEOMAR Helmholtz Centre for Ocean Research/Kiel University, dissertation: "Nitrogen Isotopes in the Global Ocean", 2013
  • M.Sc., Oceanography, College of Oceanic and Atmospheric Sciences, Oregon State University, thesis: "Nitrogen Isotopes in a Global Ocean Biogeochemical Model", 2010
  • B.Sc., Physics (Geophysics option), Oregon State University, thesis: "Modeling instabilities of the global thermohaline circulation and its effect on the Pacific Ocean oxygen minimum zone", 2006
  • A.Eng., Software Engineering Technology, Oregon Institute of Technology, 2003

Past Projects

    Impacts of anthropogenic nutrient pollutants on marine productivity, deoxygenation and sedimentary feedbacks in the Anthropocene: From the coastal to the global ocean (project page)

    • Postdoctoral research grant funded by the Cluster of Excellence "The Future Ocean" from the German Research Foundation (DFG)
    • Position: Project Leader
    • 2017-2019

    Climate-Biogeochemistry Interactions in the Tropical Ocean (project page)

    • Collaborative Research Centre funded by the German Research Foundation (DFG)
    • Position: PhD, Postdoctroal Researcher
    • 2010-2017

    Reconstructing Glacial Nitrogen and Carbon Cycling Using Isotopes (project page)

    • funded by Marine Geology and Geophysics program from the National Science Foundation
    • Position: External Collaborator
    • 2011-2014

    Ocean Circulation, Oxgyen and Nutrient Cycles during the Last Glacial (project page)

    • funded by Marine Geology and Geophysics program from the National Science Foundation
    • Position: Masters' Student Researcher
    • 2007-2010