Katharina Six

Department Climate Variability
Group Ocean Physics
Position Research Scientist
phone +49 40 41173-163
Email katharina.six@mpimet.mpg.de
Room B 226



Research interest

Initially trained as a physical oceanographer, I have been involved in modelling the cycles of marine biogeochemistry for decades. The role of marine biology in carbon storage was as much a part of my research as the future evolution of planktonic sulphur emissions, whose decrease due to the ongoing ocean acidification may play a significant contribution to anthropogenic warming.

My current research focus is on the biogeochemistry of the Mediterranean during the last deglaciation. Comprehensive sediment archives show strong variations in sedimentation processes of planktonic and benthic organisms. In particular, during the early Holocene (6000-10 000 years before present), deposits of organic rich layers, so-called sapropels, are found in regions of the Mediterranean Sea that are now characterised by extremely low biological activity. Based on the group's paleo simulations with the global MPI-ESM and a regional model of the Mediterranean Sea, I investigate the different physical and biogeochemical driving forces that have led to the observed sediment variations.


Under review:

  • Six, K. D. and Mikolajewicz, U. and Schmiedl, G., Modeling Mediterranean ocean biogeochemistry of the Last Glacial Maximum, Climate of the Past Discussions, doi.org/10.5194/cp-2024-9


  • Liu, B., Six, K.D. & Ilyina, T. Incorporating the stable carbon isotope 13C in the ocean biogeochemical component of the Max Planck Institute Earth System Model Biogeosciences, 18, 4389–4429, doi.org/10.5194/bg-18-4389-2021
  • Liu, F., Mikolajewicz, U. & Six, K.D. Drivers of the decadal variability of the North Ionian Gyre upper layer circulation during 1910–2010: a regional modelling study. Clim Dyn (2021). doi.org/10.1007/s00382-021-05714-y



  • Mauritsen, T., Bader, J., Becker, T., Behrens, J., Bittner, M., Brokopf, R., Brovkin, V., Claussen, M., Crueger, T., Esch, M., Fast, I., Fiedler, S., Popke, D., Gayler, V., Giorgetta, M., Goll, D., Haak, H., Hagemann, S., Hedemann, C., Hohenegger, C., Ilyina, T., Jahns, T., Jimenez Cuesta de la Otero, D., Jungclaus, J., Kleinen, T., Kloster, S., Kracher, D., Kinne, S., Kleberg, D., Lasslop, G., Kornblueh, L., Marotzke, J., Matei, D., Meraner, K., Mikolajewicz, U., Modali, K., Möbis, B., Müller, W., Nabel, J., Nam, C., Notz, D., Nyawira, S., Paulsen, H., Peters, K., Pincus, R., Pohlmann, H., Pongratz, J., Popp, M., Raddatz, T., Rast, S., Redler, R., Reick, C., Rohrschneider, T., Schemann, V., Schmidt, H., Schnur, R., Schulzweida, U., Six, K., Stein, L., Stemmler, I., Stevens, B., von Storch, J., Tian, F., Voigt, A., de Vrese, P., Wieners, K.-H., Wilkenskjeld, S., Roeckner, E. & Winkler, A. (2019). Developments in the MPI-M Earth System Model version 1.2 (MPI-ESM1.2) and its response to increasing CO2. Journal of Advances in Modeling Earth Systems, 11, 998-1038. doi:10.1029/2018MS001400


  • Paulsen, H., Ilyina, T., Jungclaus, J. H., Six, K. D., and Stemmler, I. (2018): Light absorption by marine cyanobacteria affects tropical climate mean state and variability, Earth Syst. Dynam., 9, 1283-1300, doi.org/10.5194/esd-9-1283-2018
  • Mikolajewicz, U., Ziemen, F., Cioni, G., Claussen, M., Fraedrich, K., Heidkamp, M., Hohenegger, C., Jimenez de la Cuesta, D., Kapsch, M.-L., Lemburg, A., Mauritsen, T., Meraner, K., Röber, N., Schmidt, H., Six, K. D., Stemmler, I., Tamarin-Brodsky, T., Winkler, A., Zhu, X., and Stevens, B. (2018): The climate of a retrograde rotating Earth, Earth Syst. Dynam., 9, 1191-1215, doi.org/10.5194/esd-9-1191-2018.
  • Pätsch, J. , Kühn, W., and Six,K.D.: Interannual sedimentary effluxes of alkalinity in the southern North Sea: model results compared with summer observations, Biogeosciences, doi.org/10.5194/bg-15-3293-2018
  • Landschützer, P., Gruber, N., Bakker, D., Stemmler, I. & Six, K.D. (2018). Strengthening seasonal marine CO2 variations due to increasing atmospheric CO2. Nature Climate Change , doi:10.1038/s41558-017-0057-x


  • J.Schwinger, J. Tjiputra, N. Goris, K. Six, A. Kirkevåg, Ø. Seland, C. Heinze, and T. Ilyina, Amplification of global warming through pH-dependence of DMS-production simulated with a fully coupled Earth system model, Biogeosciences, doi:10.5194/bg-14-3633-2017
  • Paulsen, H., T. Ilyina., K. D. Six., and I. Stemmler, Incorporating a prognostic representation of marine nitrogen fixers into the global ocean biogeochemical model HAMOCC, J. Adv. Model. Earth Syst., DOI: 10.1002/2016MS000737


  • Grimm,R., D. Notz, R.N. Glud, S. Rysgaard, and K.D. Six: Assessment of the sea-ice carbon pump: Insights from a three-dimensional ocean-sea-ice-biogeochemical model (MPIOM/HAMOCC). Elementa, doi:10.12952/journal.elementa.000136


  • Hoffman, F.M., J.T. Randerson, V.K. Arora, Q. Bao, P. Cadule, D. Ji, C.D. Jones, M. Kawamiya, S. Khatiwala, K. Lindsay, A. Obata, E. Shevliakova, K.D. Six, J.F. Tjiputra, E.M. Volodin, and T. Wu Causes and implications of persistent atmospheric carbon dioxide biases in Earth System Models. Journal of Geophysical Research-Biogeosciences, 119, 141-162, DOI: 10.1002/2013JG002381
  • Steiner, N. S., J. R. Christian, K. D. Six, A. Yamamoto, and M. Yamamoto-Kawai, Future ocean acidification in the Canada Basin and surrounding Arctic Ocean from CMIP5 earth system models, J. Geophys. Res. Oceans, 119, 332–347, doi:10.1002/2013JC009069


  • Six K.D., Kloster S., Ilyina T., Archer S.D., Zhang.K, Maier-Reimer,E., Global warming amplified by reduced sulphur fluxes as a result of ocean acidification. Nature Climate Change, doi:10.1038/nclimate1981
  • Giorgetta M.A., Jungclaus J., Reick C.H., Legutke S., Bader J., Böttinger J., Brovkin B., Crueger T., Esch M., Fieg K., Glushak K., Gayler V., Haak H., Hollweg H.D., Ilyina T., Kinne S., Kornblueh L., Matei D., Mauritsen T., Mikolajewicz U., Mueller W., Notz D., Pithan F., Raddatz T., Rast S., Redler R., Roeckner E., Schmidt H., Schnur R., Segschneider J., Six K.D., Stockhause M., Timmreck C., Wegner J., Widmann H., Wieners K.H., Claussen M., Marotzke J., Stevens B.: Climate and carbon cycle changes from 1850 to 2100 in MPI-ESM simulations for the coupled model intercomparison project phase 5. Journal of Advances in Modeling Earth Systems, doi:10.1002/jame.20038
  • Ilyina T., Six K.D., Segschneider J., Maier-Reimer E., Li H., Núñez-Riboni I.: Global ocean biogeochemistry model HAMOCC: Model architecture and performance as component of the MPI-Earth System Model in different CMIP5 experimental realizations. Journal of Advances in Modeling Earth Systems, doi: 10.1029/2012MS000178
  • Segschneider, J., Beitsch, A., Timmreck, C., Brovkin, V., Ilyina, T., Jungclaus, J., Lorenz, S. J., Six, K. D., and Zanchettin, D.: Impact of an extremely large magnitude volcanic eruption on the global climate and carbon cycle estimated from ensemble Earth System Model simulations, Biogeosciences, 10, 669-687, doi:10.5194/bg-10-669-2013.


  • J.H. Jungclaus et al. (24, incl K.Six) Climate and carbon-cycle variability over the last millennium. Climate of the Past, 6, 723-737
  • Brovkin, V., S. Lorenz, J. Jungclaus, T. Raddatz, C. Reick, C. Timmreck, J. Segschneider, K. Six, 2010. Sensitivity of a coupled climate-carbon cycle model to large volcanic eruptions during the last millennium. Tellus B, 62 (5), 674-682
  • Le Clainche, Y., A. Vezina, M. Levasseur, R. A. Cropp, J. R. Gunson, S. M. Vallina, M. Vogt, C. Lancelot, J. I. Allen, S. D. Archer, L. Bopp, C. Deal, S. Elliott, M. Jin, G. Malin, V. Schoemann, R. Simo, K. D. Six and J. Stefels: A first appraisal of prognostic ocean DMS models and prospects for their use in climate models. Global Biogeochemical Cycles 24, Art. No. GB3021, doi: 10.1029/2009GB003721


  • Kloster, S., K.D. Six, J. Feichter, E.Maier-Reimer, E. Roeckner, P. Wetzel, P. Stier, and M. Esch, Response of dimethylsulfide (DMS) in the ocean and atmosphere to global warming, Journal of Geophysical Research-Biogeosciences 112, Seq. No.: G03005 (2007). doi: 10.1029/2006JG000224


  • Six, K.D. and E. Maier-Reimer, What controls the oceanic dimethylsulfide (DMS) cycle? A modelling approach, Global Biogeochem.Cycles, 20 , doi:10.1029/2005GB002674
  • Kloster, S., J. Feichter, E. Maier-Reimer, K. D. Six, P. Stier and P. Wetzel: DMS cycle in the marine ocean-atmosphere system – a global model study. Biogeosciences 3, 1, 29-51 (2006). doi: 1726-4189/bg/2006-3-29


  • Hoffmann, G.,M. Cuntz, C.Weber, P.Ciais, P. Friedlingstein, M. Heimann, J. Jouzel, J. Kaduk, E. Maier-Reimer, U. Seibt, and K. Six, A model of the Earth’s Dole effect, Global Biogeochem. Cycles, 18, doi:10.1029/2003GB002059


  • Hofmann, M.,D.A. Wolf-Gladrow, T. Takahashi, S.C. Sutherland, K.D. Six, and E.Maier-Reimer, Stable carbon isotope distribution of particulate organic matter in the ocean: a model study, Marine Chemistry, 72, 131 - 150


  • Stephens, B.B., Keeling, R.F., Heimann, M., Six, K.D., Murnane, R., Caldeira, K., Testing global ocean carbon cycle models using measurements of atmospheric O2 and CO2 concentration, Global Biogeochem. Cycles, 12, 2, 213-230


  • Six, K.D. and E. Maier-Reimer, Effects of Plankton Dynamics on Seasonal Carbon Fluxes in an Ocean General Circulation Model, Global Biogeochem. Cycles, 10, 4, 559-583, 1996.
  • Erickson III,D.J., P.J. Rasch, P.P. Tans, P. Friedlingstein, P. Ciais, E. Maier- Reimer, K. Six, C.A. Fischer, and S. Walters, The seasonal cycle of atmoshperic CO2: A study based on the NCAR Community Climate Model (CCM2), J. Geophys. Res., 101, D10, 15079-15097, 1996.
  • P.K. Quinn, K.J. Barrett, F.J. Dentener, F. Lipschultz, and K.D. Six, Estimation of the Air/Sea Exchange of Ammonia for the North Atlantic Basin Biogeochemistry, 35, 1, 275-304, 1996.


  • Kurz, K. D.(maiden name), and E. Maier-Reimer (1993), Iron fertilization of the austral ocean—The Hamburg Model Assessment, Global Biogeochem. Cycles, 7(1), 229–244, doi:10.1029/92GB02910.


  • Quadfasel, D.; Rudels, B.; Kurz, K.. “Outflow of dense water from a Svalbard fjord into the Fram Strait”. Deep Sea Research A: Oceanographic Research Papers 35 (7). (1988): S. 1143-1150, doi:10.1016/0198-0149(88)90006-4.

Curriculum vitae

since August 2002 research scientist at MPI for Meteorology (part time)

1997 - 2002 parental leave



1996-1997 Institute of Oceanography, University of Hamburg 

1993-1996 MPI for Meteorology, Hamburg 



1993 in physical oceanography at the University of Hamburg


ORCID : 0000-0002-4594-2793 , SCOPUS : 6602543142